69 results on '"Van Schalkwyk C"'
Search Results
2. Impact of interventions for tuberculosis prevention and care in South Africa - a systematic review of mathematical modelling studies
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Brown, L R, van Schalkwyk, C, de Villiers, A K, and Marx, F M
- Abstract
BACKGROUND: Substantial additional efforts are needed to prevent, find and successfully treat tuberculosis (TB) in South Africa (SA). In the past decade, an increasing body of mathematical modelling research has investigated the population-level impact of TB prevention and care interventions. To date, this evidence has not been assessed in the SA context OBJECTIVE: To systematically review mathematical modelling studies that estimated the impact of interventions towards the World Health Organization's End TB Strategy targets for TB incidence, TB deaths and catastrophic costs due to TB in SA METHODS: We searched the PubMed, Web of Science and Scopus databases for studies that used transmission-dynamic models of TB in SA and reported on at least one of the End TB Strategy targets at population level. We described study populations, type of interventions and their target groups, and estimates of impact and other key findings. For studies of country-level interventions, we estimated average annual percentage declines (AAPDs) in TB incidence and mortality attributable to the intervention RESULTS: We identified 29 studies that met our inclusion criteria, of which 7 modelled TB preventive interventions (vaccination, antiretroviral treatment (ART) for HIV, TB preventive treatment (TPT)), 12 considered interventions along the care cascade for TB (screening/case finding, reducing initial loss to follow-up, diagnostic and treatment interventions), and 10 modelled combinations of preventive and care-cascade interventions. Only one study focused on reducing catastrophic costs due to TB. The highest impact of a single intervention was estimated in studies of TB vaccination, TPT among people living with HIV, and scale-up of ART. For preventive interventions, AAPDs for TB incidence varied between 0.06% and 7.07%, and for care-cascade interventions between 0.05% and 3.27% CONCLUSION: We describe a body of mathematical modelling research with a focus on TB prevention and care in SA. We found higher estimates of impact reported in studies of preventive interventions, highlighting the need to invest in TB prevention in SA. However, study heterogeneity and inconsistent baseline scenarios limit the ability to compare impact estimates between studies. Combinations, rather than single interventions, are likely needed to reach the End TB Strategy targets in SA more...
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- 2023
Catalog
3. Bowtie technique—a novel approach to correct the widened ventral labia majora after male-to-female gender reassignment surgery
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Liang, D. G., Dusseldorp, J. R., van Schalkwyk, C., and Haertsch, P. A.
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- 2016
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4. Impact of interventions for tuberculosis prevention and care in South Africa - a systematic review of mathematical modelling studies.
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Brown, L. R., van Schalkwyk, C., de Villiers, A. K., and Marx, F. M.
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- 2023
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5. Neonatal sepsis: Challenges in data access, harmonisation and analysis to inform empirical antibiotic recommendations in South African neonatal units.
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Bolton, L., Bekker, A., Govender, N., van Schalkwyk, C., Whitelaw, A., and Dramowski, A.
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- 2023
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6. Coke formation on WO 3/SiO 2 metathesis catalysts
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Moodley, D.J., van Schalkwyk, C., Spamer, A., Botha, J.M., and Datye, A.K.
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- 2007
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7. Extracellular polymer production and potential for aggregate formation by classical propionibacteria
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van Schalkwyk, C., Joubert, H., and Britz, T.J.
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- 2003
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8. Silication of γ-alumina catalyst during the dehydration of linear primary alcohols
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Makgoba, N.P., Sakuneka, T.M., Koortzen, J.G., van Schalkwyk, C., Botha, J.M., and Nicolaides, C.P.
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- 2006
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9. Algorithm for the introduction of rapid-acting insulin analogues in patients with type 2 diabetes on basal insulin therapy
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Owens, D R, van Schalkwyk, C, Smith, P, Beer, S, Goenka, N, Bain, S C, Bootle, S, Robertson, D, Robinson, A, and Shaw, J AM
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- 2009
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10. Application of a WO 3/SiO 2 catalyst in an industrial environment: part II
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Spamer, A., Dube, T.I., Moodley, D.J., van Schalkwyk, C., and Botha, J.M.
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- 2003
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11. The reduction of isomerisation activity on a WO 3/SiO 2 metathesis catalyst
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Spamer, A, Dube, T.I, Moodley, D.J, van Schalkwyk, C, and Botha, J.M
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- 2003
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12. Factors that could influence the activity of a WO 3/SiO 2 catalyst: Part III
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van Schalkwyk, C., Spamer, A., Moodley, D.J., Dube, T., Reynhardt, J., Botha, J.M., and Vosloo, H.C.M.
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- 2003
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13. An investigation into the activity of the in situ ruthenium(III) chloride catalytic system for the metathesis of 1-octene
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van Schalkwyk, C., Vosloo, H.C.M., and Botha, J.M.
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- 2002
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14. The association between sources of financial advice and retirement confidence among working pre-retirees in South Africa.
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Visagie, J. and van Schalkwyk, C. H.
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SOUTH Africans ,RETIREMENT ,CONFIDENCE ,INVESTMENT advisors ,ADVICE - Abstract
Owing to the concern that individuals are not adequately preparing for retirement, factors that affect retirement savings and confidence have been the focus of research in the field of household finance. By making use of data from a nationally representative sample of South African individuals, this study aimed to determine whether working pre-retirees' retirement confidence can be associated with the source of financial advice used (formal, informal, workplace or social network), while controlling for sociodemographic factors and financial knowledge. The results indicated that among working pre-retirees, higher levels of income and education were positively associated with retirement confidence, and respondents who made use of formal financial advice were more likely to feel confident about their financial preparation for retirement than respondents who did not. These findings have implications for financial advisors, consumers and policymakers. [ABSTRACT FROM AUTHOR] more...
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- 2020
15. Reviews
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van Schalkwyk, C.
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Sinonieme, antonieme, hiponieme, superordinate, leks!kografie, tesourus, konsepkategoriee, behoeftebepaling, gebruikersvriendelik, semantiese struktuur, gebruiksleiding, rekenaartegnologie, woordverwerker, konseptuele raamwerk, rassisties, indeks - Abstract
L.G. de Stadler en Amanda de Stadler (Medewerker). Groot Tesourusvan Afrikaans, Iste uitgawe, Iste druk 1994, xxxiii + 863 pp. ISBN186~12 478 9. Halfweghuis: Southern Boekuitgewers. Prys R89,99.De Stadler se Groot Tesourus van Afrikaans word in oenskou geneem. Kwessies wat aan die bod gestel word, is vrae soos: Wat is 'n tesourus? Wat is die funksie van 'n tesourus? Wie is die tipiese tesourusgebruiker? Waarvoor is dit geskik? Hoe moet dit saamgestel word? Wat moet daarin opgeneem word? Voldoen Groot Tesourus van Afrikaans aan hierdie kriteria? more...
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- 2016
16. National differences in the financial risk tolerance of financial planning clients.
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Mabalane, M. D., van Schalkwyk, C. H., and Reyers, M.
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FINANCIAL risk ,FINANCIAL planning ,LOGISTIC regression analysis ,NET worth ,U.S. states - Abstract
This study provides policy makers and financial planners with key information to identify demographic traits that are associated with the financial risk tolerance (FRT) of financial planning clients in order to be able to target them appropriately. It explores international nationality differences and similarities in financial risk tolerance based on previously collected survey data, using logistic regression analysis. Data were obtained from 6 828 financial planning clients in Australia, the United Kingdom, the United States and South Africa. Each country's log-regression model contained seven independent variables (age, gender, education, income, marital status, number of dependants and net worth). The results revealed national differences in the financial risk tolerance, with a younger and predominantly male South African sample showing the highest financial risk tolerance. In all the countries, being young and male was associated with higher financial risk tolerance levels. In Australia and the United Kingdom, higher income levels were associated with higher levels of financial risk tolerance, while in the United States and South Africa, those with higher levels of net worth demonstrated higher levels of financial risk tolerance. In addition, in the South African sample those with higher levels of education had higher financial risk tolerance scores. The full multivariate model (n = 3 981), which included all demographic variables, revealed that higher financial risk tolerance levels are associated with younger, more educated South African males with both higher levels of income and accumulated net worth. [ABSTRACT FROM AUTHOR] more...
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- 2019
17. Symptom screening rules to identify active pulmonary tuberculosis: Findings from the Zambian South African Tuberculosis and HIV/AIDS Reduction (ZAMSTAR) trial prevalence surveys.
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Claassens, M. M., van Schalkwyk, C., Floyd, S., Ayles, H., and Beyers, N.
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TUBERCULOSIS diagnosis , *MEDICAL screening , *SYMPTOMS , *HIV prevention , *DISEASE prevalence , *HEALTH surveys - Abstract
Background: High tuberculosis (TB) burden countries should consider systematic screening among adults in the general population. We identified symptom screening rules to be used in addition to cough ≥2 weeks, in a context where X-ray screening is not feasible, aiming to increase the sensitivity of screening while achieving a specificity of ≥85%. Methods: We used 2010 Zambia South Africa Tuberculosis and HIV/AIDS Reduction (ZAMSTAR) survey data: a South African (SA) training dataset, a SA testing dataset for internal validation and a Zambian dataset for external validation. Regression analyses investigated relationships between symptoms or combinations of symptoms and active disease. Sensitivity and specificity were calculated for candidate rules. Results: Among all participants, the sensitivity of using only cough ≥2 weeks as a screening rule was less than 25% in both SA and Zambia. The addition of any three of six TB symptoms (cough <2 weeks, night sweats, weight loss, fever, chest pain, shortness of breath), or 2 or more of cough <2 weeks, night sweats, and weight loss, increased the sensitivity to ~38%, while reducing specificity from ~95% to ~85% in SA and ~97% to ~92% in Zambia. Among HIV-negative adults, findings were similar in SA, whereas in Zambia the increase in sensitivity was relatively small (15% to 22%). Conclusion: High TB burden countries should investigate cost-effective strategies for systematic screening: one such strategy could be to use our rule in addition to cough ≥2 weeks. [ABSTRACT FROM AUTHOR] more...
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- 2017
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18. Missed pulmonary TB screening opportunities at Primary Healthcare Facilities: An Exit Study, Eastern Cape Province, South Africa
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Kweza, P.F., Abraham, N., Claassens, M.M., Van Schalkwyk, C., and Medino-Marino, A.
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- 2016
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19. Coke formation on WO3/SiO2 metathesis catalysts
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Moodley, D.J., van Schalkwyk, C., Spamer, A., Botha, J.M., and Datye, A.K.
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COKE (Coal product) , *COAL carbonization , *METATHESIS reactions , *CATALYSTS , *TRANSMISSION electron microscopy - Abstract
Abstract: An appreciable amount of coke forms over an 8wt% WO3/SiO2 during the metathesis of 1-alkenes to internal alkenes. Catalyst activity is maintained despite the high coke levels (49wt%). To understand this phenomenon, the coked catalyst was characterized by thermogravimetric analysis (TGA), BET and energy filtered transmission electron microscopy (EFTEM). Even at high coke levels, carbon maps show that the coke is dispersed over the support rather than covering the tungsten oxide. This observation may explain why the high activity of the catalyst is maintained and gives an indication that the location of coke laydown is more important than the amount deposited, in determining catalyst activity. Trace quantities of water, butanol and 2-pentanone were introduced into the feed stream and this resulted in the inhibition of coke formation without a significant loss in catalyst activity. 2-Pentanone was found to be the most effective inhibitor. Coking profiles indicated that the internal alkenes coked more rapidly than the 1-alkene feed. [Copyright &y& Elsevier] more...
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- 2007
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20. Factors that could influence the activity of a WO3/SiO2 catalyst: Part III
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van Schalkwyk, C., Spamer, A., Moodley, D.J., Dube, T., Reynhardt, J., Botha, J.M., and Vosloo, H.C.M.
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CATALYSTS , *METATHESIS reactions , *ADDITIVES , *CHEMICAL reactors - Abstract
An 8% WO3/SiO2 catalyst was used for a metathesis reaction of 1-octene in the presence of different additives. These additives represents the possible components in an industrial 1-heptene feed stream that might have an influence on the performance of a WO3/SiO2 metathesis catalyst. The reaction conditions for the metathesis reaction in a once-through mode reactor were 460 °C and a Liquid Hour Space Velocity (LHSV) of 5 h−1. The operating conditions for the recycle reactor were 460 °C,
LHSV=16 h−1 and a feed to recycle ratio of 1:5.6. The oxygenates used for the poison testing were 2-pentanone, hexanal, acetic acid, butanol and water. Both Brønsted acids and Lewis bases used, slows the reaction rate down if the amount of oxygenates are more than 500 ppm. The reaction was unstable with more than 500 ppm of oxygenates present in the feed, but this resulted in a product with a clearer colour (more colourless). Changing the feed back to pure feed resulted in reactivation of the catalyst. The catalyst was thereafter more selective and active towards the primary metathesis products, indication a permanent change in morphology of the catalyst. [Copyright &y& Elsevier] more...- Published
- 2003
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21. A Comparison of the Activity of Homogeneous Tungsten and Ruthenium Catalysts for the Metathesis of 1-Octene.
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van Schalkwyk, C., Vosloo, H. C. M., and du Plessis, J. A. K.
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- 2002
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22. Translating Jabberwocky into Brabbelwoggel.
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van Schalkwyk, C.
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- 1983
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23. An AC-to-AC converter based voltage regulator.
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van Schalkwyk, C., Beukes, H.J., and du T Mouton, H.
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- 2002
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24. W(O-2,6-C 6H 3X 2) 2Cl 4/Bu 4Sn as metathesis catalyst of 1-alkenes
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van Schalkwyk, C., Vosloo, H.C.M., and du Plessis, J.A.K.
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- 1998
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25. The reduction of isomerisation activity on a WO3/SiO2 metathesis catalyst
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Spamer, A., Dube, T.I., Moodley, D.J., van Schalkwyk, C., and Botha, J.M.
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METATHESIS reactions , *CATALYSTS , *TUNGSTEN , *ALKALI metals - Abstract
By increasing the WO3 loading on WO3/SiO2 metathesis catalysts it was observed that metathesis activity is closely related to the tungsten surface compound and not to the crystalline WO3. It was observed that metathesis activity reached a maximum while WO3 crystalline material continued to increase with increasing WO3 loading. At high WO3 loadings the formation of crystalline material also protected the active tungsten surface compound from deactivation by being the preferred species for over-reduction. The occurrence of branched metathesis products was attributed to an increase in Brønsted acidity indicating an alkoxide (carbenium ion) mechanism responsible for skeletal isomerisation. Reduction of branched metathesis products were achieved with the addition of small amounts of an alkali-metal ion. Large amounts of the alkali-metal ion resulted in a sharp decline in conversion indicating destruction of the Lewis acidity necessary for metathesis activity. Preparation of WO3/SiO2 catalysts at a pH above the iso-electric point of silica also had a significant effect on catalyst selectivity. [Copyright &y& Elsevier] more...
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- 2003
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26. Application of a WO3/SiO2 catalyst in an industrial environment: part II
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Spamer, A., Dube, T.I., Moodley, D.J., van Schalkwyk, C., and Botha, J.M.
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CATALYSTS , *FEED utilization efficiency , *COKE (Coal product) , *COAL carbonization - Abstract
During investigations into the activity of the 8% WO3/SiO2 catalyst it was observed that the selectivity and online lifetime of the catalyst improved, while the overall feed conversion decreased slightly after the first regeneration. It was further observed that the online lifetime of the catalyst was different after the first regeneration of the catalyst. Analysis of the fresh, coked and regenerated catalyst did not show any sintering of the catalyst taking place. It was concluded that coking of the catalyst is mostly occurring in the pores of the support. Analysis also indicated a possible change in the morphology of the catalyst after the first regeneration. The purpose of this investigation is to highlight the significant effect that regeneration has on the lifetime and selectivity of a WO3/SiO2 metathesis catalyst. [Copyright &y& Elsevier] more...
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- 2003
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27. Epidemiology of healthcare-associated bloodstream infection in South African neonatal units.
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Dramowski A, Bolton L, Bekker A, Engelbrecht A, Erasmus L, Fataar A, Geldenhuys C, Kunneke M, Roux DL, Connell NO, Reddy K, Rhoda N, Tooke L, Wates M, Wessels T, van Schalkwyk C, and Whitelaw A
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- Humans, South Africa epidemiology, Infant, Newborn, Cross-Sectional Studies, Male, Female, Bacteremia epidemiology, Bacteremia microbiology, Bacteremia mortality, Intensive Care Units, Neonatal statistics & numerical data, Infant, Very Low Birth Weight, Cross Infection epidemiology, Cross Infection microbiology, Anti-Bacterial Agents therapeutic use
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Background: Reports of healthcare-associated bloodstream infection (HA-BSI) epidemiology in African neonatal units are limited., Methods: We conducted a cross-sectional study (2017-2018) in nine neonatal units in the Western Cape Province, South Africa, including central, regional and district hospitals (416 beds) using laboratory and clinical records. Patient demographics, HA-BSI rates, pathogen spectrum, and hospital outcomes and empiric antibiotic coverage rates were determined., Results: Over two years, 23,748 neonates were admitted with unit occupancy rates ranging from 79 to 93%. 485 HA-BSI episodes occurred, with median onset at 11 (IQR 7-24) days of life. Most HA-BSI episodes (348; 72%) affected very low birth weight neonates (< 1500 g). The overall HA-BSI rate was 2.0/1000 patient days. The highest HA-BSI rate was observed at the central unit with onsite surgery (3.8/1000 patient days). Crude HA-BSI mortality was 31.8% (154/485) with two-thirds of deaths occurring within three days of BSI onset. Higher mortality was observed for Gram-negative/fungal BSI compared to Gram-positive BSI (RR 1.5; 95%CI 1.1-2.0; p = 0.01) and very preterm neonates (gestation < 32 weeks) versus ≥ 32 weeks (RR 1.5; 95%CI 1.1-2.1; p = 0.01). Mean estimated empiric antibiotic coverage rates varied by unit type: 66-79% for piperacillin-tazobactam plus amikacin, 60-76% for meropenem and 84-92% for meropenem plus vancomycin., Conclusion: Most HA-BSI events affected preterm neonates at the central hospital with onsite surgery. One-third of patients with HA-BSI died, with highest mortality in preterm infants and Gram-negative/fungal BSI. Empiric antibiotic regimens provide moderate coverage of circulating pathogens but require annual review given increasing carbapenem resistance rates., Competing Interests: Declarations. Ethical approval: The Stellenbosch University Health Research Ethics Committee (SU HREC) and the Tygerberg Hospital management reviewed and approved the study protocol SU HREC approvals (N18/07/068, N20/07/070), in accordance with the Declaration of Helsinki standards. The Stellenbosch University Health Research Ethics Committee (SU HREC) approved a waiver of individual informed consent for the retrospective analysis of neonatal bloodstream infection data. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).) more...
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- 2024
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28. Excess mortality attributable to AIDS among people living with HIV in high-income countries: a systematic review and meta-analysis.
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Trickey A, Ambia J, Glaubius R, van Schalkwyk C, Imai-Eaton JW, Korenromp EL, and Johnson LF
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- Humans, Male, Female, Adult, Acquired Immunodeficiency Syndrome mortality, Acquired Immunodeficiency Syndrome drug therapy, Developed Countries statistics & numerical data, HIV Infections mortality, HIV Infections drug therapy, HIV Infections complications
- Abstract
Introduction: Identifying strategies to further reduce AIDS-related mortality requires accurate estimates of the extent to which mortality among people living with HIV (PLHIV) is due to AIDS-related or non-AIDS-related causes. Existing approaches to estimating AIDS-related mortality have quantified AIDS-related mortality as total mortality among PLHIV in excess of age- and sex-matched mortality in populations without HIV. However, recent evidence suggests that, with high antiretroviral therapy (ART) coverage, a growing proportion of excess mortality among PLHIV is non-AIDS-related., Methods: We searched Embase on 22/09/2023 for English language studies that contained data on AIDS-related mortality rates among adult PLHIV and age-matched comparator all-cause mortality rates among people without HIV. We extracted data on the number and rates of all-cause and AIDS-related deaths, demographics, ART use and AIDS-related mortality definitions. We calculated the proportion of excess mortality among PLHIV that is AIDS-related. The proportion of excess mortality due to AIDS was pooled using random-effects meta-analysis., Results: Of 4485 studies identified by the initial search, eight were eligible, all from high-income settings: five from Europe, one from Canada, one from Japan and one from South Korea. No studies reported on mortality among only untreated PLHIV. One study included only PLHIV on ART. In all studies, most PLHIV were on ART by the end of follow-up. Overall, 1,331,742 person-years and 17,471 deaths were included from PLHIV, a mortality rate of 13.1 per 1000 person-years. Of these deaths, 7721 (44%) were AIDS-related, an overall AIDS-related mortality rate of 5.8 per 1000 person-years. The mean overall mortality rate among the general population was 2.8 (95% CI: 1.8-4.0) per 1000 person-years. The meta-analysed percentage of excess mortality that was AIDS-related was 53% (95% CI: 45-61%); 52% (43-60%) in Western and Central Europe and North America, and 71% (69-74%) in the Asia-Pacific region., Discussion: Although we searched all regions, we only found eligible studies from high-income countries, mostly European, so, the generalizability of these results to other regions and epidemic settings is unknown., Conclusions: Around half of the excess mortality among PLHIV in high-income regions was non-AIDS-related. An emphasis on preventing and treating comorbidities linked to non-AIDS mortality among PLHIV is required., (© 2024 The Author(s). Journal of the International AIDS Society published by John Wiley & Sons Ltd on behalf of International AIDS Society.) more...
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- 2024
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29. Estimation of the poliovirus type 2 immunity gap in South Africa.
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Brown L, Bingham J, Pulliam J, Mthombothi Z, Sereo T, Kamupira M, Botha S, Molema K, Maseti E, Schönfeldt M, Mabhena N, Prabdial-Sing N, von Gottberg A, McCarthy K, and van Schalkwyk C
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- Humans, South Africa epidemiology, Infant, Child, Preschool, Vaccination statistics & numerical data, Vaccine Efficacy statistics & numerical data, Poliomyelitis prevention & control, Poliomyelitis immunology, Poliomyelitis epidemiology, Poliovirus immunology, Poliovirus Vaccine, Inactivated administration & dosage, Poliovirus Vaccine, Inactivated immunology, Immunization Programs, Vaccination Coverage statistics & numerical data, Disease Eradication methods
- Abstract
In the context of polio eradication efforts, accurate assessment of vaccination programme effectiveness is essential to public health planning and decision making. Such assessments are often based on zero-dose children, estimated using the number of children who did not receive the first dose of the Diphtheria-Tetanus-Pertussis containing vaccine as a proxy. Our study introduces a novel approach to directly estimate the number of children susceptible to poliovirus type 2 (PV2) and uses this approach to provide district-level estimates for South Africa of susceptible children born between 2017 and 2022. We used district-level data on annual doses of inactivated poliovirus vaccine (IPV) administered, live births, and population sizes, from 2017 through 2022. We imputed missing vaccination data, implemented flexible assumptions regarding dose distribution in the eligible population, and used estimated efficacy values for one, two, three, and four doses of IPV, to compute the number of susceptible and immune children by birth year. We validated our approach by comparing an intermediary output with zero-dose children (ZDC) estimated using data reported by WHO/UNICEF Estimates of National Immunization Coverage (WUENIC). Our results indicate high heterogeneity in susceptibility to PV2 across South Africa's 52 districts as of the end of 2022. In children under 5 years, PV2 susceptibility ranged from approximately 30 % in districts including Xhariep (31.9 %), Ekurhuleni (30.1 %), and Central Karoo (29.8 %), to less than 4 % in Sarah Baartman (1.9 %), Buffalo City (2.1 %), and eThekwini (3.2 %). Our susceptibility estimates were consistently higher than ZDC over the timeframe. We estimated that ZDC decreased nationally from 155,168 (152,737-158,523) in 2017 to 108,593 in 2021, and increased to 127,102 in 2022, a trend consistent with ZDC derived from data reported by WUENIC. While our approach provides a more comprehensive profile of PV2 susceptibility, our susceptibility and ZDC estimates generally agree in the ranking of districts according to risk., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.) more...
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- 2024
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30. Facility-Based Indicators to Manage and Scale Up Cervical Cancer Prevention and Care Services for Women Living With HIV in Sub-Saharan Africa: a Three-Round Online Delphi Consensus Method.
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Davidović M, Asangbeh SL, Taghavi K, Dhokotera T, Jaquet A, Musick B, Van Schalkwyk C, Schwappach D, Rohner E, Murenzi G, Wools-Kaloustian K, Anastos K, Omenge OE, Boni SP, Duda SN, von Groote P, and Bohlius J more...
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- Humans, Female, Consensus, Delphi Technique, Africa South of the Sahara epidemiology, HIV Infections diagnosis, HIV Infections drug therapy, HIV Infections prevention & control, Uterine Cervical Neoplasms diagnosis, Uterine Cervical Neoplasms prevention & control
- Abstract
Background: Of women with cervical cancer (CC) and HIV, 85% live in sub-Saharan Africa, where 21% of all CC cases are attributable to HIV infection. We aimed to generate internationally acceptable facility-based indicators to monitor and guide scale up of CC prevention and care services offered on-site or off-site by HIV clinics., Methods: We reviewed the literature and extracted relevant indicators, grouping them into domains along the CC control continuum. From February 2021 to March 2022, we conducted a three-round, online Delphi process to reach consensus on indicators. We invited 106 experts to participate. Through an anonymous, iterative process, participants adapted the indicators to their context (round 1), then rated them for 5 criteria on a 5-point Likert-type scale (rounds 2 and 3) and then ranked their importance (round 3)., Results: We reviewed 39 policies from 21 African countries and 7 from international organizations; 72 experts from 15 sub-Saharan Africa countries or international organizations participated in our Delphi process. Response rates were 34% in round 1, 40% in round 2, and 44% in round 3. Experts reached consensus for 17 indicators in the following domains: primary prevention (human papillomavirus prevention, n = 2), secondary prevention (screening, triage, treatment of precancerous lesions, n = 11), tertiary prevention (CC diagnosis and care, n = 2), and long-term impact of the program and linkage to HIV service (n = 2)., Conclusion: We recommend that HIV clinics that offer CC control services in sub-Saharan Africa implement the 17 indicators stepwise and adapt them to context to improve monitoring along the CC control cascade., Competing Interests: S.L.A. received the Swiss Government Excellence Scholarship, No 2019.0741. The remaining authors have no funding or conflicts of interest to disclose., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc.) more...
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- 2024
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31. Updated Data and Methods for the 2023 UNAIDS HIV Estimates.
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van Schalkwyk C, Mahy M, Johnson LF, and Imai-Eaton JW
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- Humans, Dietary Supplements, HIV Infections epidemiology, HIV Infections prevention & control, Acquired Immunodeficiency Syndrome epidemiology, Acquired Immunodeficiency Syndrome prevention & control, Epidemics
- Abstract
Abstract: Each year, supported by the Joint United Nations Programme on HIV/AIDS (UNAIDS), country teams across the globe produce estimates that chart the state of their HIV epidemics. In 2023, HIV estimates were available for 174 countries, accounting for 99% of the global population, of which teams from 150 countries actively engaged in this process. The methods used to derive these estimates are developed under the guidance of the UNAIDS Reference Group on Estimates, Modeling, and Projections (www.epidem.org). Updates to these methods and epidemiological analyses that inform parameters and assumptions are documented in this supplement., Competing Interests: The authors have no funding or conflicts of interest to disclose., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc.) more...
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- 2024
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32. The role of wastewater-based epidemiology for SARS-CoV-2 in developing countries: Cumulative evidence from South Africa supports sentinel site surveillance to guide public health decision-making.
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Iwu-Jaja C, Ndlovu NL, Rachida S, Yousif M, Taukobong S, Macheke M, Mhlanga L, van Schalkwyk C, Pulliam JRC, Moultrie T, le Roux W, Schaefer L, Pocock G, Coetzee LZ, Mans J, Bux F, Pillay L, de Villiers D, du Toit AP, Jambo D, Gomba A, Groenink S, Madgewick N, van der Walt M, Mutshembele A, Berkowitz N, Suchard M, and McCarthy K more...
- Abstract
The uptake of wastewater-based epidemiology (WBE) for SARS-CoV-2 as a complementary tool for monitoring population-level epidemiological features of the COVID-19 pandemic in low-and-middle-income countries (LMICs) is low. We report on the findings from the South African SARS-CoV-2 WBE surveillance network and make recommendations regarding the implementation of WBE in LMICs. Eight laboratories quantified influent wastewater collected from 87 wastewater treatment plants in all nine South African provinces from 01 June 2021 to 31 May 2022 inclusive, during the 3rd and 4th waves of COVID-19. Correlation and regression analyses between wastewater levels of SARS-CoV-2 and district laboratory-confirmed caseloads were conducted. The sensitivity and specificity of novel 'rules' based on WBE data to predict an epidemic wave were determined. Amongst 2158 wastewater samples, 543/648 (85 %) samples taken during a wave tested positive for SARS-CoV-2 compared with 842 positive tests from 1512 (55 %) samples taken during the interwave period. Overall, the regression-co-efficient was 0,66 (95 % confidence interval = 0,6-0,72, R
2 = 0.59), ranging from 0.14 to 0.87 by testing laboratory. Early warning of the 4th wave of SARS-CoV-2 in Gauteng Province in November-December 2021 was demonstrated. A 50 % increase in log copies of SARS-CoV-2 compared with a rolling mean over the previous five weeks was the most sensitive predictive rule (58 %) to predict a new wave. Our findings support investment in WBE for SARS-CoV-2 surveillance in LMICs as an early warning tool. Standardising test methodology is necessary due to varying correlation strengths across laboratories and redundancy across testing plants. A sentinel site model can be used for surveillance networks without affecting WBE finding for decision-making. Further research is needed to identify optimal test frequency and the need for normalisation to population size to identify predictive and interpretive rules to support early warning and public health action., Competing Interests: Declaration of competing interest All authors declare no competing interests., (Copyright © 2023. Published by Elsevier B.V.) more...- Published
- 2023
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33. Differential in-hospital mortality and intensive care treatment over time: Informing hospital pathways for modelling COVID-19 in South Africa.
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Jamieson L, Van Schalkwyk C, Nichols BE, Meyer-Rath G, Silal S, Pulliam J, Blumberg L, Cohen C, Moultrie H, and Jassat W
- Abstract
There are limited published data within sub-Saharan Africa describing hospital pathways of COVID-19 patients hospitalized. These data are crucial for the parameterisation of epidemiological and cost models, and for planning purposes for the region. We evaluated COVID-19 hospital admissions from the South African national hospital surveillance system (DATCOV) during the first three COVID-19 waves between May 2020 and August 2021. We describe probabilities and admission into intensive care units (ICU), mechanical ventilation, death, and lengths of stay (LOS) in non-ICU and ICU care in public and private sectors. A log-binomial model was used to quantify mortality risk, ICU treatment and mechanical ventilation between time periods, adjusting for age, sex, comorbidity, health sector and province. There were 342,700 COVID-19-related hospital admissions during the study period. Risk of ICU admission was 16% lower during wave periods (adjusted risk ratio (aRR) 0.84 [0.82-0.86]) compared to between-wave periods. Mechanical ventilation was more likely during a wave overall (aRR 1.18 [1.13-1.23]), but patterns between waves were inconsistent, while mortality risk in non-ICU and ICU were 39% (aRR 1.39 [1.35-1.43]) and 31% (aRR 1.31 [1.27-1.36]) higher during a wave, compared to between-wave periods, respectively. If patients had had the same probability of death during waves vs between-wave periods, we estimated approximately 24% [19%-30%] of deaths (19,600 [15,200-24,000]) would not have occurred over the study period. LOS differed by age (older patients stayed longer), ward type (ICU stays were longer than non-ICU) and death/recovery outcome (time to death was shorter in non-ICU); however, LOS remained similar between time periods. Healthcare capacity constraints as inferred by wave period have a large impact on in-hospital mortality. It is crucial for modelling health systems strain and budgets to consider how input parameters related to hospitalisation change during and between waves, especially in settings with severely constrained resources., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Jamieson et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.) more...
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- 2023
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34. Impact of interventions for tuberculosis prevention and care in South Africa - a systematic review of mathematical modelling studies.
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Brown LK, Van Schalkwyk C, De Villiers AK, and Marx FM
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- Humans, South Africa, Anti-Retroviral Agents, Databases, Factual, Tuberculosis, HIV Infections
- Abstract
Background: Substantial additional efforts are needed to prevent, find and successfully treat tuberculosis (TB) in South Africa (SA). In thepast decade, an increasing body of mathematical modelling research has investigated the population-level impact of TB prevention and careinterventions. To date, this evidence has not been assessed in the SA context., Objective: To systematically review mathematical modelling studies that estimated the impact of interventions towards the World HealthOrganization's End TB Strategy targets for TB incidence, TB deaths and catastrophic costs due to TB in SA., Methods: We searched the PubMed, Web of Science and Scopus databases for studies that used transmission-dynamic models of TB in SAand reported on at least one of the End TB Strategy targets at population level. We described study populations, type of interventions andtheir target groups, and estimates of impact and other key findings. For studies of country-level interventions, we estimated average annualpercentage declines (AAPDs) in TB incidence and mortality attributable to the intervention., Results: We identified 29 studies that met our inclusion criteria, of which 7 modelled TB preventive interventions (vaccination,antiretroviral treatment (ART) for HIV, TB preventive treatment (TPT)), 12 considered interventions along the care cascade for TB(screening/case finding, reducing initial loss to follow-up, diagnostic and treatment interventions), and 10 modelled combinationsof preventive and care-cascade interventions. Only one study focused on reducing catastrophic costs due to TB. The highest impactof a single intervention was estimated in studies of TB vaccination, TPT among people living with HIV, and scale-up of ART. Forpreventive interventions, AAPDs for TB incidence varied between 0.06% and 7.07%, and for care-cascade interventions between 0.05%and 3.27%., Conclusion: We describe a body of mathematical modelling research with a focus on TB prevention and care in SA. We found higherestimates of impact reported in studies of preventive interventions, highlighting the need to invest in TB prevention in SA. However, studyheterogeneity and inconsistent baseline scenarios limit the ability to compare impact estimates between studies. Combinations, rather thansingle interventions, are likely needed to reach the End TB Strategy targets in SA. more...
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- 2023
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35. Estimating the effect of HIV on cervical cancer elimination in South Africa: Comparative modelling of the impact of vaccination and screening.
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Boily MC, Barnabas RV, Rönn MM, Bayer CJ, van Schalkwyk C, Soni N, Rao DW, Staadegaard L, Liu G, Silhol R, Brisson M, Johnson LF, Bloem P, Gottlieb S, Broutet N, and Dalal S
- Abstract
Background: In 2020, the World Health Organization (WHO) launched its initiative to eliminate cervical cancer as a public health problem. To inform global efforts for countries with high HIV and cervical cancer burden, we assessed the impact of human papillomavirus (HPV) vaccination and cervical cancer screening and treatment in South Africa, on cervical cancer and the potential for achieving elimination before 2120, considering faster HPV disease progression and higher cervical cancer risk among women living with HIV(WLHIV) and HIV interventions., Methods: Three independent transmission-dynamic models simulating HIV and HPV infections and disease progression were used to predict the impact on cervical cancer incidence of three scenarios for all women: 1) girls' vaccination (9-14 years old), 2) girls' vaccination plus 1 lifetime cervical screen (at 35 years), and 3) girls' vaccination plus 2 lifetime cervical screens (at 35 and 45 years) and three enhanced scenarios for WLHIV: 4) vaccination of young WLHIV aged 15-24 years, 5) three-yearly cervical screening of WLHIV aged 15-49 years, or 6) both. Vaccination assumed 90% coverage and 100% lifetime protection with the nonavalent vaccine (against HPV-16/18/31/33/45/52/58). Cervical cancer screening assumed HPV testing with uptake increasing from 45% (2023), 70% (2030) to 90% (2045+). We also assumed that UNAIDS 90-90-90 HIV treatment and 70% male circumcision targets are reached by 2030. We examined three elimination thresholds: age-standardised cervical cancer incidence rates below 4 or 10 per 100,000 women-years, and >85% reduction in cervical cancer incidence rate. We conducted sensitivity analyses and presented the median age-standardised predictions of outcomes of the three models (minimum-maximum across models)., Findings: Girls' vaccination could reduce age-standardised cervical cancer incidence from a median of 47.6 (40.9-79.2) in 2020 to 4.5 (3.2-6.3) per 100,000 women-years by 2120, averting on average ∼4% and ∼46% of age-standardised cumulative cervical cancer cases over 25 and 100 years, respectively, compared to the basecase . Adding 2 lifetime screens helped achieve elimination over the century among all women (2120 cervical cancer incidence: 3.6 (1.9-3.6) per 100,000 women-years), but not among WLHIV (10.8 (5.3-11.6)), and averted more cumulative cancer cases overall (∼45% over 25 years and ∼61% over 100 years compared to basecase ) than girls' vaccination alone. Adding three-yearly cervical screening among WLHIV (to girls' vaccination and 2 lifetime cervical screens) further reduced age-standardised cervical cancer incidence to 3.3 (1.8-3.6) per 100,000 women-years overall and to 5.2 (3.9-8.5) among WLHIV by 2120 and averted on average 12-13% additional cumulative cancer cases among all women and 21-24% among WLHIV than girls' vaccination and 2 lifetime cervical screens over 25 years or longer. Long-term vaccine protection and using the nonavalent vaccine was required for elimination., Interpretation: High HPV vaccination coverage of girls and 2 lifetime cervical screens could eliminate cervical cancer among women overall in South Africa by the end of the century and substantially decrease cases among all women and WLHIV over the short and medium term. Cervical cancer elimination in WLHIV would likely require enhanced prevention strategies for WLHIV. Screening of WLHIV remains an important strategy to reduce incidence and alleviate disparities in cervical cancer burden between women with and without HIV, despite HIV interventions scale-up., Funding: World Health Organization. National Cancer Institute, National Institutes of Health. MRC Centre for Global Infectious Disease Analysis, UK Medical Research Council. National Institute of Child Health and Human Development research. Cancer Association of South Africa. Canadian Institutes of Health Research and the Fonds de recherche du Québec - Santé research., Competing Interests: RVB reports grants from the Bill and Melinda Gates Foundation (BMGF), the 10.13039/100000002National Institutes of Health (10.13039/100000002NIH), and manuscript and abstract writing support from Regeneron Pharmaceuticals outside the submitted work. MMR reports funding from Harvard Data Science Institute and travel support to attend meetings for cervical cancer elimination from the WHO and Canadian Institute of Health Research, all outside of the submitted work. CJB did a Graduate Research Assistantship with Merck & Co., Inc. after and outside of the submitted work. GL started working from Merck in March 2022 and detains Merck stock/stock options. MB received funding from the 10.13039/100012016Institut National de Santé Publique du Québec for other work. DWR reports additional NIH, USAID and WHO salary support for unrelated work. LS received funding from 10.13039/100014588Sanofi Pasteur for projects outside the scope of this manuscript. PB, SG, NS, RS, LFJ, SG, and NB declare no competing interests., (© 2022 The Authors.) more...
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- 2022
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36. The Impact of Early Antiretroviral Treatment (ART) for HIV on the Sensitivity of the Latest Generation of Blood Screening and Point of Care Assays.
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Vermeulen M, van Schalkwyk C, Jacobs G, van den Berg K, Stone M, Bakkour S, Custer B, Jentsch U, Busch MP, Murphy E, and Grebe E
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- Anti-Retroviral Agents therapeutic use, HIV Antibodies, Humans, Point-of-Care Systems, HIV Infections diagnosis, HIV Infections drug therapy, HIV-1
- Abstract
Introduction: Rapid initiation of antiretroviral therapy (ART) in early HIV infection is important to limit seeding of the viral reservoir. A number of studies have shown that if ART is commenced prior to seroconversion, the seroconversion may, or may not, occur. We aimed to assess whether seroreversion or no seroconversion occurs using samples collected during an early treatment study in South Africa., Methods: We tested 10 longitudinal samples collected over three years from 70 blood donors who initiated ART after detection of acute or early HIV infection during donation screening on fourth- and fifth-generation HIV antibody and RNA assays, and three point of care (POC) rapid tests. Donors were allocated to three treatment groups: (1) very early, (2) early, and (3) later. Longitudinal samples were grouped into time bins post-treatment initiation., Results: On all three high-throughput HIV antibody assays, no clear pattern of declining signal intensity was observed over time after ART initiation in any of the treatment initiation groups and 100% detection was obtained. The Abbott Determine POC assay showed 100% detection at all time points with no seroreversion. However, the Abbott ABON HIV1 and OraSure OraQuick POC assays showed lower proportions of detection in all time bins in the very early treated group, ranging from 50.0% (95% CI: 26.8-73.2%) to 83.1% (95% CI: 64.2-93.0%), and moderate detection rates in the early and later-treated groups., Conclusion: While our findings are generally reassuring for HIV detection when high-throughput serological screening assays are used, POC assays may have lower sensitivity for detection of HIV infection after early treatment. Findings are relevant for blood safety and other settings where POC assays are used. more...
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- 2022
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37. Increased risk of SARS-CoV-2 reinfection associated with emergence of Omicron in South Africa.
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Pulliam JRC, van Schalkwyk C, Govender N, von Gottberg A, Cohen C, Groome MJ, Dushoff J, Mlisana K, and Moultrie H
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- Humans, Reinfection epidemiology, South Africa epidemiology, COVID-19 epidemiology, SARS-CoV-2 genetics
- Abstract
We provide two methods for monitoring reinfection trends in routine surveillance data to identify signatures of changes in reinfection risk and apply these approaches to data from South Africa's severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic to date. Although we found no evidence of increased reinfection risk associated with circulation of the Beta (B.1.351) or Delta (B.1.617.2) variants, we did find clear, population-level evidence to suggest immune evasion by the Omicron (B.1.1.529) variant in previously infected individuals in South Africa. Reinfections occurring between 1 November 2021 and 31 January 2022 were detected in individuals infected in all three previous waves, and there has been an increase in the risk of having a third infection since mid-November 2021. more...
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- 2022
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38. Modelling the impact of prevention strategies on cervical cancer incidence in South Africa.
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van Schalkwyk C, Moodley J, Welte A, and Johnson LF
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- AIDS Vaccines administration & dosage, Adult, Aged, Alphapapillomavirus isolation & purification, Early Detection of Cancer methods, Female, Follow-Up Studies, HIV isolation & purification, HIV Infections complications, HIV Infections virology, Humans, Incidence, Middle Aged, Papillomavirus Infections complications, Papillomavirus Infections virology, Papillomavirus Vaccines administration & dosage, Prognosis, South Africa epidemiology, Uterine Cervical Neoplasms diagnosis, Uterine Cervical Neoplasms virology, Young Adult, Alphapapillomavirus drug effects, HIV drug effects, HIV Infections prevention & control, Models, Statistical, Papillomavirus Infections prevention & control, Uterine Cervical Neoplasms epidemiology
- Abstract
In 2020, the World Health Organisation (WHO) published a strategy to eliminate cervical cancer as a public health concern. In South Africa, despite having a national screening policy in place since 2000, diagnosed cervical cancer incidence has shown no signs of decline. We extend a previously developed individual-based model for human immunodeficiency virus (HIV) and human papillomavirus (HPV) infection to include progression to cervical cancer. The model accounts for future reductions in HIV incidence and prevalence and includes a detailed cervical cancer screening algorithm, based on individual-level data from the public health sector. We estimate the impact of the current prevention programme and alternative screening scenarios on cervical cancer incidence. The South African screening programme prevented 8600 (95%CI 4700-12 300) cervical cancer cases between 2000 and 2019. At current levels of prevention (status quo vaccination, screening, and treatment), age-standardised cervical cancer incidence will reduce from 49.4 per 100 000 women (95%CI 36.6-67.2) in 2020, to 12.0 per 100 000 women (95%CI 8.0-17.2) in 2120. Reaching WHO's prevention targets by 2030 could help South Africa reach elimination (at the 10/100 000 threshold) by 2077 (94% probability of elimination by 2120). Using new screening technologies could reduce incidence to 4.7 per 100 000 women (95%CI 2.8-6.7) in 2120 (44% probability of elimination at the 4/100 000 threshold). HPV vaccination and decreasing HIV prevalence will substantially reduce cervical cancer incidence in the long term, but improvements to South Africa's current screening strategy will be required to prevent cases in the short term. Switching to new screening technologies will have the greatest impact., (© 2021 UICC.) more...
- Published
- 2021
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39. Mortality during tuberculosis treatment in South Africa using an 8-year analysis of the national tuberculosis treatment register.
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Osman M, van Schalkwyk C, Naidoo P, Seddon JA, Dunbar R, Dlamini SS, Welte A, Hesseling AC, and Claassens MM
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- Adolescent, Adult, Aged, Aged, 80 and over, Coinfection complications, Coinfection microbiology, Female, HIV Infections complications, HIV-1 pathogenicity, Humans, Male, Middle Aged, Mycobacterium tuberculosis pathogenicity, Retrospective Studies, Risk Factors, South Africa epidemiology, Tuberculosis drug therapy, Tuberculosis mortality, Coinfection mortality, Tuberculosis, Pulmonary drug therapy, Tuberculosis, Pulmonary mortality
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In 2011, the South African HIV treatment eligibility criteria were expanded to allow all tuberculosis (TB) patients lifelong ART. The impact of this change on TB mortality in South Africa is not known. We evaluated mortality in all adults (≥ 15 years old) treated for drug-susceptible TB in South Africa between 2009 and 2016. Using a Cox regression model, we quantified risk factors for mortality during TB treatment and present standardised mortality ratios (SMR) stratified by year, age, sex, and HIV status. During the study period, 8.6% (219,618/2,551,058) of adults on TB treatment died. Older age, male sex, previous TB treatment and HIV infection (with or without the use of ART) were associated with increased hazard of mortality. There was a 19% reduction in hazard of mortality amongst all TB patients between 2009 and 2016 (adjusted hazard ratio: 0.81 95%CI 0.80-0.83). The highest SMR was in 15-24-year-old women, more than double that of men (42.3 in 2016). Between 2009 and 2016, the SMR for HIV-positive TB patients increased, from 9.0 to 19.6 in women, and 7.0 to 10.6 in men. In South Africa, case fatality during TB treatment is decreasing and further interventions to address specific risk factors for TB mortality are required. Young women (15-24-year-olds) with TB experience a disproportionate burden of mortality and interventions targeting this age-group are needed., (© 2021. The Author(s).) more...
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- 2021
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40. Modelling of HIV prevention and treatment progress in five South African metropolitan districts.
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van Schalkwyk C, Dorrington RE, Seatlhodi T, Velasquez C, Feizzadeh A, and Johnson LF
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- Adult, Animals, Anti-Retroviral Agents therapeutic use, Female, Humans, Male, Mice, Inbred C57BL, South Africa, Mice, Disease Progression, HIV Infections drug therapy, HIV Infections prevention & control, Models, Biological
- Abstract
Globally, large proportions of HIV-positive populations live in cities. The Fast-Track cities project aims to advance progress toward elimination of HIV as a public health threat by accelerating the response in cities across the world. This study applies a well-established HIV transmission model to provide key HIV estimates for the five largest metropolitan districts in South Africa (SA): Cape Town, Ekurhuleni, eThekwini, Johannesburg and Tshwane. We calibrate the model to metro-specific data sources and estimate progress toward the 90-90-90 targets set by UNAIDS (90% of people living with HIV (PLHIV) diagnosed, 90% of those diagnosed on antiretroviral therapy (ART) and viral suppression in 90% of those on ART). We use the model to predict progress towards similarly defined 95-95-95 targets in 2030. In SA, 90.5% of PLHIV were diagnosed in 2018, with metro estimates ranging from 86% in Johannesburg to 92% in eThekwini. However, only 68.4% of HIV-diagnosed individuals nationally were on ART in 2018, with the proportion ranging from 56% in Tshwane to 73% in eThekwini. Fractions of ART users who were virally suppressed ranged from 77% in Ekurhuleni to 91% in eThekwini, compared to 86% in the whole country. All five metros are making good progress to reach diagnosis targets and all (with the exception of Ekurhuleni) are expected to reach viral suppression targets in 2020. However, the metros and South Africa face severe challenges in reaching the 90% ART treatment target. more...
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- 2021
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41. Projected early spread of COVID-19 in Africa through 1 June 2020.
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Pearson CA, Van Schalkwyk C, Foss AM, O'Reilly KM, and Pulliam JR
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- Africa epidemiology, Betacoronavirus, COVID-19, China epidemiology, Forecasting, Humans, Models, Statistical, Mortality, SARS-CoV-2, Time Factors, Coronavirus, Coronavirus Infections epidemiology, Coronavirus Infections transmission, Disease Outbreaks, Pandemics, Pneumonia, Viral epidemiology, Pneumonia, Viral transmission
- Abstract
For 45 African countries/territories already reporting COVID-19 cases before 23 March 2020, we estimate the dates of reporting 1,000 and 10,000 cases. Assuming early epidemic trends without interventions, all 45 were likely to exceed 1,000 confirmed cases by the end of April 2020, with most exceeding 10,000 a few weeks later. more...
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- 2020
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42. Birth outcomes following antiretroviral exposure during pregnancy: Initial results from a pregnancy exposure registry in South Africa.
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Mehta UC, van Schalkwyk C, Naidoo P, Ramkissoon A, Mhlongo O, Maharaj NR, Naidoo N, Fieggen K, Urban MF, Krog S, Welte A, Dheda M, Pillay Y, and Moran NF
- Abstract
Background: In 2013, a pregnancy exposure registry and birth defects surveillance (PER/BDS) system was initiated in eThekwini District, KwaZulu-Natal (KZN), to assess the impact of antiretroviral treatment (ART) on birth outcomes., Objectives: At the end of the first year, we assessed the risk of major congenital malformations (CM) and other adverse birth outcomes (ABOs) detected at birth, in children born to women exposed to ART during pregnancy., Method: Data were collected from women who delivered at Prince Mshiyeni Memorial Hospital, Durban, from 07 October 2013 to 06 October 2014, using medicine exposure histories and birth outcomes from maternal interviews, clinical records and neonatal surface examination. Singleton births exposed to only one ART regimen were included in bivariable analysis for CM risk and multivariate risk analysis for ABO risk., Results: Data were collected from 10 417 women with 10 517 birth outcomes (4013 [38.5%] HIV-infected). Congenital malformations rates in births exposed to Efavirenz during the first trimester (T1) (RR 0.87 [95% CI 0.12-6.4; p = 0.895]) were similar to births not exposed to ART during T1. However, T1 exposure to Nevirapine was associated with the increased risk of CM (RR 9.28 [95% CI 2.3-37.9; p = 0.002]) when compared to the same group. Other ABOs were more frequent in the combination of HIV/ART-exposed births compared to HIV-unexposed births (29.9% vs. 26.0%, adjusted RR 1.23 [1.14-1.31; p < 0.001])., Conclusion: No association between T1 use of EFV-based ART regimens and CM was observed. Associations between T1 NVP-based ART regimen and CM need further investigation. HIV- and ART-exposed infants had more ABOs compared to HIV-unexposed infants., Competing Interests: The authors have no conflict of interests., (© 2019. The Authors.) more...
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- 2019
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43. Estimated impact of human papillomavirus vaccines on infection burden: The effect of structural assumptions.
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van Schalkwyk C, Moodley J, Welte A, and Johnson LF
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- Adolescent, Adult, Female, Human papillomavirus 16 immunology, Human papillomavirus 16 pathogenicity, Human papillomavirus 18 immunology, Human papillomavirus 18 pathogenicity, Humans, Male, Papillomavirus Infections virology, Vaccination methods, Young Adult, Papillomavirus Infections prevention & control, Papillomavirus Vaccines therapeutic use
- Abstract
Mathematical models have been used to estimate the impact of human papillomavirus (HPV) vaccines on infection burden and cervical cancer. Models assume different mechanisms of naturally acquired immunity against re-infection, but processes of latency and reactivation of latent infection have not been explored. This study uses an individual-based dynamic model to simulate randomised controlled trials (RCTs) for vaccine efficacy, using different assumptions about naturally acquired immunity and viral latency after clearance of HPV infection. Model estimates of vaccine effectiveness are compared to those from published RCTs. We then estimate the impact of the bivalent vaccine on HPV-16 and -18 infection burden in South Africa under these different assumptions. When assuming no latency, simulated vaccine effectiveness overestimates results from RCTs and the model cannot match the observed difference in vaccine effectiveness between total vaccinated cohorts and more HPV-naïve cohorts. The reduction in HPV-16 and -18 burden by 2045, following roll-out of vaccination in 2014, does not depend on assumptions about natural immunity, but models that assume no latency predict ∼25% greater reduction in HPV-16 and -18 burden than models that include reactivation of latent infection for all men and women. Mathematical models that do not allow for reactivation of latent HPV infections may therefore overestimate the long-term impact of HPV vaccines., (Copyright © 2019 Elsevier Ltd. All rights reserved.) more...
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- 2019
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44. Evaluation of the Performance of Three Biomarker Assays for Recent HIV Infection Using a Well-Characterized HIV-1 Subtype C Incidence Cohort.
- Author
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Gonese E, Kilmarx PH, van Schalkwyk C, Grebe E, Mutasa K, Ntozini R, Parekh B, Dobbs T, Duong Pottinger Y, Masciotra S, Owen M, Nachega JB, van Zyl G, and Hargrove JW
- Subjects
- Africa epidemiology, Antibody Affinity, Biomarkers blood, CD4 Lymphocyte Count, Cohort Studies, Female, HIV Antibodies blood, HIV Antibodies immunology, HIV Infections epidemiology, HIV Seropositivity diagnosis, HIV-1 classification, HIV-1 immunology, Humans, Incidence, Postpartum Period, Viral Load, AIDS Serodiagnosis methods, HIV Infections diagnosis, HIV-1 isolation & purification, Immunoenzyme Techniques methods
- Abstract
Biomarkers for detecting early HIV infection and estimating HIV incidence should minimize false-recent rates (FRRs) while maximizing mean duration of recent infection (MDRI). We compared HIV subtypes B, E and D (BED) capture enzyme immunoassay (BED), Sedia limiting antigen (LAg) avidity enzyme immunoassay, and Bio-Rad avidity incidence (BRAI) assays using samples from Zimbabwean postpartum women infected with clade C HIV. We calculated MDRIs using 590 samples from 351 seroconverting postpartum women, and FRRs using samples from 2,825 women known to be HIV positive for >12 months. Antibody kinetics were more predictable with LAg and had higher precision compared with BED or BRAI. BRAI also exhibited more variability, and avidity reversal in some cases. For BED, LAg, and BRAI, used alone or with viral load, MDRI values in days were: BED-188 and 170 at normalized optical density (ODn) 0.8; LAg-104 and 100 at ODn cutoff 1.5; BRAI-135 and 134 at avidity index cutoff 30%. Corresponding FRRs were: BRAI 1.1% and 1.0% and LAg 0.57% and 0.35%: these were 3.8-10.9 times lower than BED values of 4.8% and 3.8%. BRAI and LAg have significantly lower FRRs and MDRIs than in published studies, and much lower than BED and could be used to estimate incidence in perinatal women and to measure population-level HIV incidence in HIV control operations in Africa. more...
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- 2019
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45. Are associations between HIV and human papillomavirus transmission due to behavioural confounding or biological effects?
- Author
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van Schalkwyk C, Moodley J, Welte A, and Johnson LF
- Subjects
- Adolescent, Adult, Bayes Theorem, Cohort Studies, Female, HIV physiology, Humans, Male, Middle Aged, Papillomaviridae physiology, Papillomavirus Infections epidemiology, Prevalence, Proportional Hazards Models, Risk Factors, Sexual Partners, South Africa epidemiology, Young Adult, Confounding Factors, Epidemiologic, HIV Infections transmission, Papillomavirus Infections transmission, Sexual Behavior
- Abstract
Objectives: Cohort studies have shown significant increased risk of HIV acquisition following human papillomavirus (HPV) detection and increased risk of new HPV detection in individuals with HIV infection, after adjusting for behavioural risk factors. This study uses an individual-based model to assess whether confounding sexual behaviour factors and network level effects can explain these associations between HIV and HPV infection status, without biological interactions., Methods: The model simulates infection with 13 oncogenic HPV types and HIV. It allows for different relationship types, with heterogeneity in probabilities of concurrency and rates of partner change. No effect of prevalent HPV infection on HIV acquisition is assumed and vice versa. The model is calibrated to South African HIV and type-specific HPV prevalence data using a Bayesian approach. The model is used to simulate cohorts with quarterly HIV and HPV testing from 2000 to 2002. These simulated data are analysed using proportional hazard models., Results: The mean of the unadjusted HRs of HIV acquisition following detection of an oncogenic HPV type calculated for each simulated cohort is 2.6 (95% CI 2.2 to 3.1). The mean of the unadjusted HRs for the effect of HIV on newly detected HPV is 2.5 (95% CI 2.2 to 2.8). Simulated associations between HIV and HPV infection status are similar to corresponding empirical estimates. In sensitivity analyses in which HIV and HPV were assumed to increase each other's transmission risk, simulated associations were stronger but not inconsistent with empirical estimates., Conclusions: Although we cannot rule out the possibility that associations between HIV and HPV transmission may be due in part to biological interactions, these results suggest that observed associations could be explained entirely by residual confounding by behavioural factors and network-level effects that observational studies cannot account for., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.) more...
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- 2019
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46. Pooled PCR testing of dried blood spots for infant HIV diagnosis is cost efficient and accurate.
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van Schalkwyk C, Maritz J, van Zyl GU, Preiser W, and Welte A
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- Costs and Cost Analysis, Early Diagnosis, Humans, Infant, Models, Economic, Retrospective Studies, Sensitivity and Specificity, South Africa, Specimen Handling, HIV Infections diagnosis, Polymerase Chain Reaction economics
- Abstract
Background: Access to qualitative HIV PCRs for early infant diagnosis (EID) is restricted in resource-limited settings due to cost. We hypothesised that pooling of dried blood spots (DBS), defined as combining multiple patient samples in a single test with subsequent individual testing of positive pools, would be cost saving while retaining clinical accuracy compared to individual patient testing., Methods: Cost savings: A model was developed to simulate reagent and consumable cost saving of pooled compared to individual sample testing. Daily sample/result data of a public health laboratory in South Africa were used to illustrate outputs from the model. Samples were randomly allocated to pools and the process was repeated 1000 times to measure variation in estimates due to this stochasticity. Clinical accuracy: 1170 patient samples were tested using the Roche CAP/CTM Qual assay in pools of five 50 μl DBS. Negative pools comprised DBS previously tested in single reactions; positive pools included 1 positive sample., Results: Pooling would have saved 64% of laboratory costs in 2015. The model is published as an R-based web tool, into which the user enters sample/positivity estimates and workflow management parameters to obtain cost saving estimates at an optimal pool size. Sensitivity of pooled testing was 98.8% overall; 100% for strongly reactive pools. One pool tested false positive which would not impact clinical specificity as individual patient testing is performed prior to reporting., Conclusions: Pooled PCR testing for EID remains accurate and dramatically reduces costs in settings with moderate to low prevalence rates and sufficient sample numbers. more...
- Published
- 2019
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47. Wing length and host location in tsetse (Glossina spp.): implications for control using stationary baits.
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Hargrove J, English S, Torr SJ, Lord J, Haines LR, van Schalkwyk C, Patterson J, and Vale G
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- Animals, Body Size, Feeding Behavior, Female, Male, Species Specificity, Flight, Animal physiology, Insect Control methods, Tsetse Flies anatomy & histology, Tsetse Flies physiology, Wings, Animal anatomy & histology
- Abstract
Background: It has been suggested that attempts to eradicate populations of tsetse (Glossina spp.) using stationary targets might fail because smaller, less mobile individuals are unlikely to be killed by the targets. If true, tsetse caught in stationary traps should be larger than those from mobile baits, which require less mobility on the part of the flies., Results: Sampling tsetse in the Zambezi Valley of Zimbabwe, we found that the number of tsetse caught from stationary traps, as a percent of total numbers from traps plus a mobile vehicle, was ~5% for male G. morsitans morsitans (mean wing length 5.830 mm; 95% CI: 5.800-5.859 mm) and ~10% for females (6.334 mm; 95% CI: 6.329-6.338 mm); for G. pallidipes the figures were ~50% for males (6.830 mm; 95% CI: 6.821-6.838 mm) and ~75% for females (7.303 mm, 95% CI: 7.302-7.305 mm). As expected, flies of the smaller species (and the smaller sex) were less likely to be captured using stationary, rather than mobile sampling devices. For flies of a given sex and species the situation was more complex. Multivariable analysis showed that, for females of both species, wing lengths changed with ovarian age and the month, year and method of capture. For G. pallidipes, there were statistically significant interactions between ovarian age and capture month, year and method. For G. m. morsitans, there was only a significant interaction between ovarian age and capture month. The effect of capture method was, however, small in absolute terms: for G. pallidipes and G. m. morsitans flies caught on the mobile vehicle had wings only 0.24 and 0.48% shorter, respectively, than flies caught in stationary traps. In summary, wing length in field samples of tsetse varies with ovarian age, capture month and year and, weakly, with capture method. Suggestions that a target-based operation against G. f. fuscipes in Kenya caused a shift towards a smaller, less mobile population of tsetse, unavailable to the targets, failed to account for factors other than capture method., Conclusions: The results are consistent with the successful use of targets to eradicate populations of tsetse in Zimbabwe. Until further, more nuanced, studies are conducted, it is premature to conclude that targets alone could not, similarly, be used to eradicate G. f. fuscipes populations in Kenya. more...
- Published
- 2019
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48. Estimating the magnitude of pulmonary tuberculosis patients missed by primary health care clinics in South Africa.
- Author
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Kweza PF, Van Schalkwyk C, Abraham N, Uys M, Claassens MM, and Medina-Marino A
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- Adolescent, Adult, Cross-Sectional Studies, Drug Resistance, Bacterial, Female, Humans, Logistic Models, Male, Mass Screening methods, Middle Aged, South Africa, Sputum microbiology, Young Adult, Delayed Diagnosis statistics & numerical data, Mass Screening statistics & numerical data, Mycobacterium tuberculosis isolation & purification, Primary Health Care statistics & numerical data, Tuberculosis, Pulmonary diagnosis
- Abstract
Setting: The present study was conducted at 20 randomly selected primary health clinics across Buffalo City Metropolitan Health District, a high TB burden district in South Africa., Objective: To estimate the proportion of TB patients missed by primary health clinics., Design: We enrolled 1255 TB-symptomatic individuals exiting primary health clinics between March and December 2015. Participants were interviewed and asked to provide sputum for Xpert® MTB/RIF testing., Results: Clinic staff screened 79.1% of participants seeking care for TB-related symptoms and 21.9% of those attending a clinic for other reasons (P < 0.001). Of those screened by clinic staff, 21.5% reported submitting sputum, although only 9.8% had available results. Study staff tested sputum from 779 participants not tested by clinic staff. Of these, 39 (5.0%) individuals tested positive for TB, three of whom were rifampicin-resistant; 15/39 (38.5%) were never screened and 24/39 (61.5%) were screened but not tested by clinic staff. We estimate that the health system missed 62.9-78.5% of TB patients attending primary health clinics for TB-related symptoms and 89.5-100% of those attending a clinic for other reasons., Conclusion: Low rates of TB screening and testing by the health system resulted in missed TB patients. Universal TB screening and testing of symptomatic individuals should be instituted in high TB burden communities in South Africa. more...
- Published
- 2018
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49. High human papillomavirus (HPV) prevalence in South African adolescents and young women encourages expanded HPV vaccination campaigns.
- Author
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Mbulawa ZZA, van Schalkwyk C, Hu NC, Meiring TL, Barnabas S, Dabee S, Jaspan H, Kriek JM, Jaumdally SZ, Muller E, Bekker LG, Lewis DA, Dietrich J, Gray G, Passmore JS, and Williamson AL
- Subjects
- Adolescent, Adult, Female, Humans, Papillomavirus Infections prevention & control, Papillomavirus Infections virology, Prevalence, South Africa epidemiology, Young Adult, Alphapapillomavirus isolation & purification, Papillomavirus Infections epidemiology, Papillomavirus Vaccines administration & dosage
- Abstract
The objectives of the study were to investigate prevalence of cervical human papillomavirus (HPV) genotypes to inform HPV vaccination strategy in South Africa and to study factors associated with HPV prevalence. Sexually active, HIV-negative women, aged 16-22 years recruited from Soweto (n = 143) and Cape Town (n = 148) were tested for cervical HPV and other genital infections. Overall HPV prevalence was 66.7% (194/291) in young women. Cape Town women were more likely to have multiple HPV infections than the Soweto women (48.0%, 71/148 versus 35.0%, 50/143 respectively, p = 0.033) and probable HR-HPV types (34.5%, 51/148 versus 21.7%, 31/143 respectively, p = 0.022). The most frequently detected HPV types were HPV-16 (11.7%), HPV-58 (10.3%), HPV-51 (8.9%), HPV-66 (8.6%), HPV-18 and HPV-81 (7.6% each). HPV types targeted by the bivalent HPV vaccine (HPV-16/18) were detected in 18.6% (54/291) of women, while those in the quadrivalent vaccine (HPV-6/11/16/18) were detected in 24.7% (72/291) of women; and those in the nonavalent vaccine (HPV-6/11/16/18/31/33/45/52/58) were detected in 38.5% (112/291) of women. In a multivariable analysis, bacterial vaginosis remained significantly associated with HPV infection (OR: 4.0, 95% CI: 1.4-12.6). Women were more likely to be HPV positive if they had received treatment for STI during the past 6-months (OR: 3.4, 95% CI: 1.1-12.4) or if they had ever been pregnant (OR: 2.3, 95% CI: 1.1-5.5). Compared to women who reported only one sexual partner, those with increased number of lifetime sex partners were more likely to have HPV (4-10 partners: OR: 2.9, 95% CI: 1.1-8.0). The high prevalence of HPV types targeted by the nonavalent HPV vaccine encourages the introduction of this vaccine and catch-up HPV vaccination campaigns in South Africa. The high burden of BV and concurrent STIs also highlights the need to improve the prevention and appropriate management of sexually-acquired and other genital tract infections in South African youth. more...
- Published
- 2018
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50. Short Communication: Heightened HIV Antibody Responses in Postpartum Women as Exemplified by Recent Infection Assays: Implications for Incidence Estimates.
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Hargrove JW, van Schalkwyk C, Humphrey JH, Mutasa K, Ntozini R, Owen SM, Masciotra S, Parekh BS, Duong YT, Dobbs T, Kilmarx PH, and Gonese E
- Subjects
- Antibody Affinity immunology, Antibody Formation immunology, Biomarkers blood, Female, HIV Antigens immunology, HIV Infections blood, HIV-1 immunology, Humans, Incidence, Serologic Tests methods, Zimbabwe, HIV Antibodies immunology, HIV Infections immunology, Postpartum Period immunology
- Abstract
Laboratory assays that identify recent HIV infections are important for assessing impacts of interventions aimed at reducing HIV incidence. Kinetics of HIV humoral responses can vary with inherent assay properties, and between HIV subtypes, populations, and physiological states. They are important in determining mean duration of recent infection (MDRI) for antibody-based assays for detecting recent HIV infections. We determined MDRIs for multi-subtype peptide representing subtypes B, E and D (BED)-capture enzyme immunoassay, limiting antigen (LAg), and Bio-Rad Avidity Incidence (BRAI) assays for 101 seroconverting postpartum women, recruited in Harare from 1997 to 2000 during the Zimbabwe Vitamin A for Mothers and Babies trial, comparing them against published MDRIs estimated from seroconverting cases in the general population. We also compared MDRIs for women who seroconverted either during the first 9 months, or at later stages, postpartum. At cutoffs (C) of 0.8 for BED, 1.5 for LAg, and 40% for BRAI, estimated MDRIs for postpartum mothers were 192, 104, and 144 days, 33%, 32%, and 52% lower than published estimates of 287, 152 and 298 days, respectively, for clade C samples from general populations. Point estimates of MDRI values were 7%-19% shorter for women who seroconverted in the first 9 months postpartum than for those seroconverting later. MDRI values for three HIV incidence biomarkers are longer in the general population than among postpartum women, particularly those who recently gave birth, consistent with heightened immunological activation soon after birth. Our results provide a caution that MDRI may vary significantly between subjects in different physiological states. more...
- Published
- 2017
- Full Text
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