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Singapore offered the BNT162b2 vaccine (tozinameran; Pfizer-BioNTech) to adolescents aged 12-17 years in May 18, 2021, and extended booster vaccines to this group in Jan 21, 2022. Literature on the effectiveness of primary series and booster vaccination among adolescents is scarce outside of Europe and North America. We aimed to determine primary series and booster vaccine effectiveness against SARS-CoV-2 infection and hospitalisation among adolescents in Singapore.For this national cohort study, we assessed the incidence of confirmed SARS-CoV-2 infection and hospitalisation among adolescents aged 12-17 years vaccinated with BNT162b2 in Singapore from Sept 1 to Dec 15, 2021, during the delta (B.1.617.2) variant wave, and from Jan 21 to April 28, 2022, during the omicron (B.1.1.529) variant wave. Data were collected from official databases maintained by the Ministry of Health of Singapore. Individuals were classified as partly vaccinated (those who had received one dose and those who had received the second dose no more than 7 days previously), fully vaccinated (8 days after receiving a second dose), or boosted (8 days after receiving a third dose) and compared with unvaccinated individuals.249 763 individuals aged 12-17 years were included in the study, contributing over 56·2 million person-days of observation. Compared with unvaccinated individuals, two vaccine doses achieved vaccine effectiveness of 66% (95% CI 63-69) against infection with the delta variant and 25% (21-29) against infection with the omicron variant, and 83% (74-89) against delta variant-associated hospitalisation and 75% (56-86) against omicron variant-associated hospitalisation. Booster vaccination with a third dose achieved vaccine effectiveness of 56% (53-58) against infection with the omicron variant and 94% (86-97) against omicron-associated hospitalisation, compared with unvaccinated adolescents. Vaccine effectiveness against infection for both variants after two doses waned over time, whereas vaccine effectiveness against hospitalisation for both variants remained stable; both were increased after three doses.Among adolescents aged 12-17 years, vaccine effectiveness against confirmed SARS-CoV-2 infection after two doses of BNT162b2 decreased over time and increased after a third dose. Boosted adolescents were also the most protected from hospitalisation compared with fully vaccinated, partly vaccinated, and unvaccinated adolescents. Therefore, the booster dose of BNT162b2 can help to reduce the burden on the health-care system and individual morbidity during an omicron wave.None.

We compared the vaccine effectiveness over time of the primary series and booster against infection and severe disease with the Delta, Omicron BA.1, and BA.2 variants in Singapore, an Asian setting with high vaccination coverage.We conducted a test-negative case-control study on all adult residents in Singapore who underwent PCR testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in acute hospitals. Individuals with a negative PCR from 1 September, 2021, to 30 November, 2021, and 1 December, 2021, to 25 April, 2022, served as controls for the Delta and Omicron variants respectively, and PCR-positive individuals within these two time periods served as cases. Associations between vaccination status and severe SARS-CoV-2 infection and severe disease with the Delta or Omicron variants were measured using Poisson regressions. Vaccine effectiveness was calculated by taking 1 minus risk ratio.There were 68 114 individuals comprising 58 495 controls and 9619 cases for the Delta period, of whom 53 093 completed the primary series and 9161 were boosted. For the Omicron period, 104 601 individuals comprising 80 428 controls, 8643 BA.1 cases, and 15 530 BA.2 cases were included, of whom 29 183 and 71 513 were vaccinated with the primary series and boosted, respectively. The primary series provided greater protection against infection with Delta (45%, 95% CI 40-50%) than against infection with Omicron (21%, 95% CI 7-34% for BA.1; 18%, 95% CI 6-29% for BA.2) at2 months from vaccination. Vaccine effectiveness of the booster was similar against infection with BA.1 (44%, 95% CI 38-50%) and BA.2 (40%, 95% CI 35-40%). Protection against severe disease by the booster for BA.1 (83%, 95% CI 76-88%) and BA.2 (78%, 95% CI 73-82%) was comparable to that by the primary series for Delta (80%, 95% CI 73-85%).Our findings support the use of a booster dose to reduce the risk of severe disease and mitigate the impact on the healthcare system in an Omicron-predominant epidemic.

Compared with individuals vaccinated with Pfizer-BioNTech/Comirnaty, recipients of Sinovac-CoronaVac and Sinopharm were 2.37 (95% CI, 2.29–2.46) and 1.62 (95% CI, 1.43–1.85) times more likely to be infected with coronavirus disease 19, respectively, while individuals vaccinated with Moderna were 0.42 (95% CI, 0.25–0.70) times less likely to develop severe disease.

Background The impact of SARS-CoV-2 variants of concern (VOCs) on disease severity is unclear. In this retrospective study, we compared the outcomes of patients infected with B.1.1.7, B.1.351, and B.1.617.2 with wild-type strains from early 2020. Methods National surveillance data from January to May 2021 were obtained and outcomes in relation to VOCs were explored. Detailed patient-level data from all patients with VOC infection admitted to our center between December 2020 and May 2021 were analyzed. Clinical outcomes were compared with a cohort of 846 patients admitted from January to April 2020. Results A total of 829 patients in Singapore in the study period were infected with these 3 VOCs. After adjusting for age and sex, B.1.617.2 was associated with higher odds of oxygen requirement, intensive care unit admission, or death (adjusted odds ratio [aOR], 4.90; 95% confidence interval [CI]: 1.43-30.78). Of these patients, 157 were admitted to our center. After adjusting for age, sex, comorbidities, and vaccination, the aOR for pneumonia with B.1.617.2 was 1.88 (95% CI: .95-3.76) compared with wild-type. These differences were not seen with B.1.1.7 and B.1.351. Vaccination status was associated with decreased severity. B.1.617.2 was associated with significantly lower polymerase chain reaction cycle threshold (Ct) values and longer duration of Ct value ≤30 (median duration 18 days for B.1.617.2, 13 days for wild-type). Conclusions B.1.617.2 was associated with increased severity of illness, and with lower Ct values and longer viral shedding. These findings provide impetus for the rapid implementation of vaccination programs.

There were 290 multidrug-resistant (MDR)-TB cases diagnosed in Singapore from 2006 to 2018. Eighty-one percent were foreign-born. Spoligotyping and MIRU-VNTR methods identified 108 patients in 24 clusters. The Beijing spoligotype accounted for 22 clusters. Whole genome sequencing (WGS) analysis reduced the number of clustered patients and clusters to 43 and nine respectively. One MIRU cluster was redefined into three WGS clusters. All the clusters had foreign-born source cases. Forty percent of local-born, versus 9% of foreign-born, MDR-TB cases belonged to WGS clusters. WGS more accurately elucidated potential MDR-TB transmission which was overestimated by conventional genotyping methods in Singapore.

Objective To describe the characteristics of healthcare workers (HCWs) infected with COVID‐19 and to examine their sources of exposure. Methods A descriptive cross‐sectional study using data extracted from the centralized disease notification system comprising individuals confirmed with COVID‐19 in Singapore between 23 January and 17 April 2020. Occupation of HCWs was categorized into six categories. Their job nature was classified into “frontline” or “back‐end” based on the frequency of direct patient contact, and source of exposure was classified as family/household, social interaction or workplace. Chi‐square and median tests were used to identify differences between categorical groups and sample medians, respectively. Results A total of 88 (1.7%) HCWs were identified from 5,050 cases. Their median age was 35 years. Chinese and Indians constituted 42.0% and 31.8%, respectively, and 43.2% were foreigners. The majority (63.6%) was serving at frontlines handling patient‐facing duties, 15.9% were doctors, 11.4% were nurses and 44.3% were ancillary staff. About 81.8% acquired the infection locally, of which 40.3% did not have a clearly identifiable source of exposure. Exposure from the family/household was most common (27.8%), followed by workplace (16.7%) and social interaction (15.3%). All HCWs were discharged well with no mortality; three (3.4%) were ever admitted to intensive care unit and required increased care. Conclusion Healthcare workers accounted for a small proportion of COVID‐19 cases in Singapore with favourable outcomes. The possibility of transmission resulting from family/household exposure and social interactions highlights the need to maintain strict vigilance and precautionary measures at all times beyond the workplace.

Summary The severe acute respiratory syndrome (SARS) outbreak in 2003 resulted in more than 8000 cases and 800 deaths. SARS was eventually contained by means of syndromic surveillance, prompt isolation of patients, strict enforcement of quarantine of all contacts, and in some areas top-down enforcement of community quarantine. By interrupting all human-to-human transmission, SARS was effectively eradicated. By contrast, by Feb 28, 2020, within a matter of 2 months since the beginning of the outbreak of coronavirus disease 2019 (COVID-19), more than 82 000 confirmed cases of COVID-19 have been reported with more than 2800 deaths. Although there are striking similarities between SARS and COVID-19, the differences in the virus characteristics will ultimately determine whether the same measures for SARS will also be successful for COVID-19. COVID-19 differs from SARS in terms of infectious period, transmissibility, clinical severity, and extent of community spread. Even if traditional public health measures are not able to fully contain the outbreak of COVID-19, they will still be effective in reducing peak incidence and global deaths. Exportations to other countries need not result in rapid large-scale outbreaks, if countries have the political will to rapidly implement countermeasures.

Objectives: The Ministry of Health (MOH), Singapore, conducted the National Paediatric Seroprevalence Survey 2018 (NPSS 2018) to estimate the latest immunity levels against measles, rubella, varicella, diphtheria, tetanus and hepatitis B, and the seroprevalence of chronic hepatitis B virus (HBV) carriage in children and adolescents in Singapore. Methods: The survey involved prospective collection of residual sera from 1,200 children and adolescents aged 1–17 years in two public acute hospitals. Enzyme-linked immunosorbent assays (EIA) or plague reduction neutralisation tests (PRNT) were used to determine the seroprevalence of the vaccine-preventable diseases. Results: Overall prevalence of measles and rubella antibodies among Singaporean children and adolescents aged 1–17 years were 98.2% (95% CI: 91.2–98.8%) and 94.8% (95% CI: 93.4–95.9%) respectively. 97.1% (95% CI: 96.0–97.9%) of subjects had at least basic protection against diphtheria, while 89.3% (95% CI: 87.5–91.0%) were protected against tetanus. The prevalence of chronic HBV carriage was 0.4% (95% CI: 0.2–1.0%), while 45.7% (95% CI: 42.9–48.5%) were immune against HBV. The seroprevalence for varicella antibodies was 52.9% (95% CI: 50.1–55.7%). Concordance between vaccination status and seroprevalence was observed for measles, rubella, diphtheria and tetanus. Conclusion: Singapore’s children and adolescents are well-protected against measles, rubella, diphtheria and tetanus. Continual efforts in ensuring high vaccination coverage should be sustained. Keywords: Seroprevalence, Survey, Vaccine, Immunity, Children, Adolescents, Singapore, Epidemiology, Public health

Background Respiratory syncytial virus (RSV) is an important respiratory pathogen that affects people of all ages. Objectives We examined the patterns of RSV circulation in 2014‐2018, and investigated their age‐specific differences in tropical Singapore. Methods Nasopharyngeal and/or throat swabs were taken from outpatient attendees for the national influenza virological surveillance among those who presented with acute respiratory illness in the community. Specimens tested negative for influenza were then tested for RSV and other respiratory pathogens. Results Among 8436 influenza‐negative specimens tested during the five‐year period, 5.8% (95% confidence interval 5.3%‐6.3%) were positive for RSV. The peak of RSV activity occurred around middle of the year. The age‐specific proportion of RSV detections showed a reverse J‐shaped pattern; RSV positivity was the highest in young children ≤2 years of age (10.9%), followed by those aged 3‐5 years (6.4%) and persons aged ≥65 years (5.3%), while the nadir was observed in the age group of 15‐24 years (1.2%). RSV type A was predominantly circulating in children ≤5 years of age from 2014 to 2015 and 2017, whereas in 2016, they were more affected by type B. Conclusion Respiratory syncytial virus was more frequently detected among the two age groups that have been recommended for influenza vaccination; persons ≥65 years of age and children 6 months to

Background: Respiratory syncytial virus (RSV) infections are one of the leading causes of lower respiratory tract infections and have a major burden on society. For prevention and control to be deployed effectively, an improved understanding of the seasonality of RSV is necessary. Objectives: The main objective of this study was to contribute to a better understanding of RSV seasonality by examining the GERi multi-country surveillance dataset. Methods: RSV seasons were included in the analysis if they contained ≥100 cases. Seasonality was determined using the "average annual percentage" method. Analyses were performed at a subnational level for the United States and Brazil. Results: We included 601 425 RSV cases from 12 countries. Most temperate countries experienced RSV epidemics in the winter, with a median duration of 10-21 weeks. Not all epidemics fit this pattern in a consistent manner, with some occurring later or in an irregular manner. More variation in timing was observed in (sub)tropical countries, and we found substantial differences in seasonality at a subnational level. No association was found between the timing of the epidemic and the dominant RSV subtype. Conclusions: Our findings suggest that geographical location or climatic characteristics cannot be used as a definitive predictor for the timing of RSV epidemics and highlight the need for (sub)national data collection and analysis. This study was funded by Sanofi/AstraZeneca. Sí

Objectives: Highly effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) have been developed but variants of concerns are worrisome, especially B.1.617.2 (Delta) which has rapidly spread across the world. We aim to study if vaccination alters virological and serological kinetics in breakthrough infections. Methods: We conducted a multicentre retrospective cohort study of patients in Singapore who had received a licensed mRNA vaccine and been admitted to hospital with B.1.617.2 SARS-CoV-2 infection. We compared clinical features, virological and serological kinetics (anti-nucleocapsid, anti-spike and surrogate virus neutralization titres) between fully vaccinated and unvaccinated individuals. Results: Out of 218 individuals with B.1.617.2 infection, 84 received an mRNA vaccine of which 71 were fully vaccinated, 130 were unvaccinated and four received a non-mRNA vaccine. Despite significantly older age in the vaccine breakthrough group, only 2.8% (2/71) developed severe COVID-19 requiring oxygen supplementation compared with 53.1% (69/130) in the unvaccinated group (p < 0.001). Odds of severe COVID-19 following vaccination were significantly lower (adjusted odds ratio 0.07 95% CI 0.015 e0.335, p 0.001). PCR cycle threshold values were similar between vaccinated and unvaccinated groups at diagnosis, but viral loads decreased faster in vaccinated individuals. Early, robust boosting of anti-spike protein antibodies was observed in vaccinated patients; however, these titres were significantly lower against B.1.617.2 than the wildtype vaccine strain. Discussion: The mRNA vaccines are highly effective at preventing symptomatic and severe COVID-19 associated with B.1.617.2 infection. Vaccination is associated with faster decline in viral RNA load and a robust serological response. Vaccination remains a key strategy for control of the COVID-19 pandemic. National Medical Research Council (NMRC) Published version B.E.Y. reports personal fees from Roche, Sanofi and Gilead, outside the submitted work. All other authors declare no competing interests. This study was funded by grants from the Singapore National Medical Research Council (COVID19RF-001, COVID19RF-008). The funders had no role in the design and conduct of the study; collection, management, analysis and interpretation of the data; preparation, review or approval of the manuscript; and decision to submit the manuscript for publication.

ObjectivesWHO recommends that low burden countries consider systematic screening and treatment of latent tuberculosis infection (LTBI) in migrants from high incidence countries. We aimed to determine LTBI prevalence and risk factors and evaluate cost-effectiveness of screening and treating LTBI in migrants to Singapore from a government payer perspective.DesignCross-sectional study and cost-effectiveness analysis.SettingMigrants in Singapore.Participants3618 migrants who were between 20 and 50 years old, have not worked in Singapore previously and stayed in Singapore for less than a year were recruited.Primary and secondary outcome measuresCosts, quality-adjusted life-years (QALYs), threshold length of stay, incremental cost-effectiveness ratios (ICERs), cost per active TB case averted.ResultsOf 3584 migrants surveyed, 20.4% had positive interferon-gamma release assay (IGRA) results, with the highest positivity in Filipinos (33.2%). Higher LTBI prevalence was significantly associated with age, marital status and past TB exposure. The cost-effectiveness model projected an ICER of S$57 116 per QALY and S$12 422 per active TB case averted for screening and treating LTBI with 3 months once weekly isoniazid and rifapentine combination regimen treatment compared with no screening over a 50-year time horizon. ICER was most sensitive to the cohort’s length of stay in Singapore, yearly disease progression rates from LTBI to active TB, followed by the cost of IGRA testing.ConclusionsFor LTBI screening and treatment of migrants to be cost-effective, migrants from high burden countries would have to stay in Singapore for ~50 years. Risk-stratified approaches based on projected length of stay and country of origin and/or age group can be considered.

While most countries in the Western Pacific Region (WPR) had similar trajectories of COVID-19 from January to May, their implementations of non-pharmaceutical interventions (NPIs) differed by transmission stages. To offer a better understanding for an implementation of multidisciplinary policies in COVID-19 control, we compared the impact of NPIs by assessing the transmissibility and severity of COVID-19 in different phases of the epidemic during the first five months in WPR. In this study, we estimated the piecewise instantaneous reproduction number (Rt) and the reporting delay-adjusted case-fatality ratio (dCFR) of COVID-19 in seven WPR jurisdictions: Hong Kong Special Administrative Region, Japan, Malaysia, Shanghai, Singapore, South Korea, and Taiwan. According to the results, implementing NPIs was associated with an apparent reduction of the piecewise Rt in two epidemic waves in general. However, large cluster outbreaks raised the piecewise Rt to a high level. We also observed relaxing the NPIs could result in an increase of Rt. The estimated dCFR ranged from 0.09% to 1.59% among the jurisdictions, except in Japan where an estimate of 5.31% might be due to low testing efforts. To conclude, in conjunction with border control measures to reduce influx of imported cases which might cause local outbreaks, other NPIs including social distancing measures along with case finding by rapid tests are also necessary to prevent potential large cluster outbreaks and transmissions from undetected cases. A comparatively lower CFR may reflect the health system capacity of these jurisdictions. In order to keep track of sustained disease transmission due to resumption of economic activities, a close monitoring of disease transmissibility is recommended in the relaxation phase. The report of transmission of SARS CoV-2 to pets in Hong Kong and to mink in farm outbreaks highlight for the control of COVID-19 and emerging infectious disease, the One Health approach is critical in understanding and accounting for how human, animals and environment health are intricately connected., Highlights • Multidisciplinary One Health policies to combat COVID-19 are required in WPR. • NPIs were associated with an apparent reduction in transmissibility of COVID-19. • However, some large cluster outbreaks raised the transmissibility to a high level. • We observed an increase in transmissibility when NPIs were partially lifted. • A lower case-fatality ratio in WPR may reflect the health system capacity.

We compared indicators of influenza activity in 2020 before and after public health measures were taken to reduce coronavirus disease (COVID-19) with the corresponding indicators from 3 preceding years. Influenza activity declined substantially, suggesting that the measures taken for COVID-19 were effective in reducing spread of other viral respiratory diseases.

Background We report our experience in evaluating the severity of local influenza epidemics using the World Health Organization Pandemic Influenza Severity Assessment framework. Methods We assessed the severity of influenza by monitoring indicators of influenza transmissibility, seriousness of disease and impact on healthcare resource utilisation. Indicators were described by various parameters collected weekly from eight government hospitals, 20 government and 30 private primary care clinics, and the national public health laboratory. Transmissibility and seriousness of disease indicators were each represented by multiple parameters, and alert thresholds were set at the 70th and 90th percentile of a parameter's past 2‐year surveillance data. We derived a collective measure for each indicator using the average percentile rank of the related parameters. Alert thresholds for the single impact parameter were set at predefined values and evaluated for its sensitivity, specificity and positive predictive value. Results For the transmissibility and seriousness of disease parameters, calculation of the percentile rank was simple and independent of a parameter's underlying distribution. For the impact parameter, predefined alert thresholds had high sensitivity and specificity (>80%) but low positive predictive value (15%‐30%). Assessment scales were used to qualitatively classify the activity of an indicator as low, moderate or high together with a confidence level. Conclusion We applied different methods for threshold setting depending on the attributes of each parameter and indicator. For indicators represented by multiple parameters, an aggregated assessment of the indicator's level of activity and confidence level of the assessment was needed for effective reporting.

Influenza outbreaks occur periodically in Long Term Care Facilities (LTCFs) and vaccination is critical in preventing influenza infections. We evaluated the influenza vaccine effectiveness (VE) during respiratory outbreaks in LTCFs reported to the Ministry of Health, Singapore in 2017. A test-negative design was used to estimate the ratio of the odds of testing positive for influenza among vaccinated individuals to the odds among unvaccinated individuals. The VE was calculated as (1-odds ratio) × 100%. For adjusted VE, the estimates were derived using logistic regression adjusted for age group, gender, month of illness, and number of days from date of illness onset till to swab collection date. Estimates by influenza subtypes and post-vaccination time periods (15–180 days & 181–365 days) were also calculated using stratified data. 264 individuals, with 118 laboratory-confirmed influenza cases [32 A(H1N1)pdm09, 75 A(H3N2), 11 A(untypable)], were included in the analysis. No one was identified to be infected with influenza B. The overall adjusted VE estimate was 40.5% (95% CI: −12.2–68.5%), while the subtype-specific adjusted VE estimates were −43.4% (95% CI: −312.4–50.2%) against A(H1N1)pdm09 and 57.1% (95% CI: 5.7–80.5%) against A(H3N2). At 15–180 days post-vaccination period, the adjusted VEs were 59.3% (95% CI: 18.0–79.8%) against all influenza, 35.4% (95% CI: −123.5–81.3%) against A(H1N1)pdm09 and 67.9% (95% CI: 22.5–86.7%) against A(H3N2). Estimates were not significant at 181–365 days post-vaccination. The influenza vaccine showed varying effectiveness among individuals in Singapore’s LTCFs in 2017, with a higher effectiveness among those who were more recently vaccinated. It remains an important tool in preventing influenza infections, especially for those who are at high risk of influenza-related complications.

Surveillance and reporting of epidemiological features of seasonal influenza mostly are aggregates across all-ages. We investigated age-specific differences in distribution of influenza virus (sub)types in tropical Singapore, using laboratory-confirmed virological data collected under the national influenza surveillance programme from 2011 to 2017. The proportion of influenza-positive specimens from outpatients with influenza-like illness was used as an indicator of influenza activity in the community. The highest influenza positivity for age groups of 5 to 14 years and 15 to 64 years coincided in the same month in 5 out of the 7 years under study. Influenza positivity was lowest in young children

Singapore implements a school closure policy for institutional hand, foot, and mouth disease (HFMD) outbreaks, but there is a lack of empirical evidence on the effect of closure on HFMD transmission. We conducted a retrospective analysis of 197,207 cases of HFMD over the period 2003–2012 at the national level and of 57,502 cases in 10,080 institutional outbreaks over the period 2011–2016 in Singapore. The effects of school closure due to 1) institutional outbreaks, 2) public holidays, and 3) school vacations were assessed using a Bayesian time series modeling approach. School closure was associated with a reduction in HFMD transmission rate. During public holidays, average numbers of secondary cases having onset the week after dropped by 53% (95% credible interval 44–62%), and during school vacations, the number of secondary cases dropped by 7% (95% credible interval 3–10%). Schools being temporarily closed in response to an institutional outbreak reduced the average number of new cases by 1,204 (95% credible interval 1,140–1,297). Despite the positive effect in reducing transmission, the effect of school closure is relatively small and may not justify the routine use of this measure.

Background We present a novel approach for exiting coronavirus disease 2019 (COVID-19) lockdowns using a ‘risk scorecard’ to prioritize activities to resume whilst allowing safe reopening. Methods We modelled cases generated in the community/week, incorporating parameters for social distancing, contact tracing and imported cases. We set thresholds for cases and analysed the effect of varying parameters. An online tool to facilitate country-specific use including the modification of parameters (https://sshsphdemos.shinyapps.io/covid_riskbudget/) enables visualization of effects of parameter changes and trade-offs. Local outbreak investigation data from Singapore illustrate this. Results Setting a threshold of 0.9 mean number of secondary cases arising from a case to keep R 1. Conclusions Countries can utilize a ‘risk scorecard’ to balance relaxations for travel and domestic activity depending on factors that reduce disease impact, including hospital/ICU capacity, contact tracing, quarantine and vaccination. The tool enabled visualization of the combinations of imported cases and activity levels on the case numbers and the trade-offs required. For vaccination, a reduction factor should be applied both for likelihood of an infected case being present and a close contact getting infected.

Prior to the implementation of social distancing measures, we monitored the close family contacts of the first 400 cases of COVID‐19 in Singapore for SARS‐CoV‐2 infection to determine the risk of infection with age. Adjusting for gender and household size, the risk of COVID‐19 infection in household contacts was found to increase with age.

Background With at least 94 countries undergoing or exiting lockdowns for contact suppression to control the COVID-19 outbreak, sustainable and public health-driven exit strategies are required. Here we explore the impact of lockdown and exit strategies in Singapore for immediate planning. Methods We use an agent-based model to examine the impacts of epidemic control over 480 days. A limited control baseline of case isolation and household member quarantining is used. We measure the impact of lockdown duration and start date on final infection attack sizes. We then apply a 3-month gradual exit strategy, immediately re-opening schools and easing workplace distancing measures, and compare this to long-term social distancing measures. Findings At baseline, we estimated 815 400 total infections (21.6% of the population). Early lockdown at 5 weeks with no exit strategy averted 18 500 (2.27% of baseline averted), 21 300 (2.61%) and 22 400 (2.75%) infections for 6, 8 and 9-week lockdown durations. Using the exit strategy averted a corresponding 114 700, 121 700 and 126 000 total cases, representing 12.07–13.06% of the total epidemic size under baseline. This diminishes to 9 900–11 300 for a late 8-week start time. Long-term social distancing at 6 and 8-week durations are viable but less effective. Interpretation Gradual release exit strategies are critical to maintain epidemic suppression under a new normal. We present final infection attack sizes assuming the ongoing importation of cases, which require preparation for a potential second epidemic wave due to ongoing epidemics elsewhere. Funding Singapore Ministry of Health, Singapore Population Health Improvement Centre.

Summary Background Elucidation of the chain of disease transmission and identification of the source of coronavirus disease 2019 (COVID-19) infections are crucial for effective disease containment. We describe an epidemiological investigation that, with use of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serological assays, established links between three clusters of COVID-19. Methods In Singapore, active case-finding and contact tracing were undertaken for all COVID-19 cases. Diagnosis for acute disease was confirmed with RT-PCR testing. When epidemiological information suggested that people might have been nodes of disease transmission but had recovered from illness, SARS-CoV-2 IgG serology testing was used to establish past infection. Findings Three clusters of COVID-19, comprising 28 locally transmitted cases, were identified in Singapore; these clusters were from two churches (Church A and Church B) and a family gathering. The clusters in Church A and Church B were linked by an individual from Church A (A2), who transmitted SARS-CoV-2 infection to the primary case from Church B (F1) at a family gathering they both attended on Jan 25, 2020. All cases were confirmed by RT-PCR testing because they had active disease, except for A2, who at the time of testing had recovered from their illness and tested negative. This individual was eventually diagnosed with past infection by serological testing. ELISA assays showed an optical density of more than 1·4 for SARS-CoV-2 nucleoprotein and receptor binding domain antigens in titres up to 1/400, and viral neutralisation was noted in titres up to 1/320. Interpretation Development and application of a serological assay has helped to establish connections between COVID-19 clusters in Singapore. Serological testing can have a crucial role in identifying convalescent cases or people with milder disease who might have been missed by other surveillance methods. Funding National Research Foundation (Singapore), National Natural Science Foundation (China), and National Medical Research Council (Singapore).

Background Respiratory syncytial virus (RSV) is one of the leading causes of acute respiratory tract infections. To optimize control strategies, a better understanding of the global epidemiology of RSV is critical. To this end, we initiated the Global Epidemiology of RSV in Hospitalized and Community care study (GERi). Methods Focal points from 44 countries were approached to join GERi and share detailed RSV surveillance data. Countries completed a questionnaire on the characteristics of their surveillance system. Results Fifteen countries provided granular surveillance data and information on their surveillance system. A median (interquartile range) of 1641 (552–2415) RSV cases per season were reported from 2000 and 2020. The majority (55%) of RSV cases occurred in the Conclusions The high number of cases in the

In May 2019, we investigated monkeypox in a traveler from Nigeria to Singapore. The public health response included rapid identification of contacts, use of quarantine, and postexposure smallpox vaccination. No secondary cases were identified. Countries should develop surveillance systems to detect emerging infectious diseases globally. Published version

The Asia Pacific region, home to two-thirds of the world's population and ten of the least developed countries, is considered a regional hot-spot for the emergence and spread of antimicrobial resistance (AMR). Despite this, there is a dearth of high-quality regional data on the extent of AMR. Recognising the urgency to close this gap, Singapore organised a meeting to discuss the problems in the region and frame a call for action. Representatives from across the region and beyond attended the meeting on the "Antimicrobial Resistance in the Asia Pacific & its impact on Singapore" held in November 2018. This meeting report is a summary of the discussions on the challenges and progress in surveillance, drivers and levers of AMR emergence, and the promising innovations and technologies that could be used to combat the increasing threat of AMR in the region. Enhanced surveillance and research to provide improved evidence-based strategies and policies are needed. The major themes that emerged for an action plan are working towards a tailored solution for the region by harnessing the One Health approach, enhancing inter-country collaborations, and collaboratively leverage upon new emerging technologies. A regionally coordinated effort that is target-driven, sustainable and builds on a framework facilitating communication and governance will strengthen the fight against AMR in the Asia Pacific region. Nanyang Technological University Published version The expenses of the symposium and networking sessions were mainly supported by the Lee Kong Chian School of Medicine, Nanyang Technological University; Pfizer; and the British High Commission..

Influenza has long been a global public health priority because of the threat of another global pandemic. Although data are available for the annual burden of seasonal influenza in many developed countries, fewer disease burden data are available for low-income and tropical countries. In recent years, however, the surveillance systems created as part of national pandemic preparedness efforts have produced substantial data on the epidemiology and impact of influenza in countries where data were sparse. These data are leading to greater interest in seasonal influenza, including implementation of vaccination programs. However, a lack of quality data on severe influenza, nonrespiratory outcomes, and high-risk groups, as well as a need for better mathematical models and economic evaluations, are some of the major gaps that remain. These gaps are the focus of multilateral research and surveillance efforts that will strengthen global efforts in influenza control in the future.

The database of the Global Influenza B Study was created by collecting surveillance datasets from each of the participating countries. These national datasets are owned by the participating countries, and thus cannot be shared publicly. Researchers interested in obtaining the country-specific datasets may contact the individuals listed below for further details regarding data access.Argentina (Santa Fe Province): Gabriela Kusznierz (labconi@yahoo.com.ar)Australia: Kate Pennington (kate.pennington@health.gov.au)Bhutan: Sonam Wangchuk (swangchuk@health.gov.bt)Brazil: Cláudio Maierovitch Pessanha Henriques (claudio.henriques@saude.gov.br)Cameroon: Guy Vernet (vernet@pasteur-yaounde.org)Chile: Rodrigo Fasce (rfasce@ispch.cl)China: Feng Luzhao (fenglz@chinacdc.cn)Costa Rica: Alexey W. Clara (wclara@cdc.gov)Ecuador: Alfredo Bruno (alfredobruno@yahoo.es)El Salvador: Alexey W. Clara (wclara@cdc.gov)England: Maria Zambon (maria.zambon@phe.gov.uk)Guatemala: Alexey W. Clara (wclara@cdc.gov)Honduras: Alexey W. Clara (wclara@cdc.gov)Indonesia: Herman Kosasih (hermaninarespond@gmail.com)Italy: Caterina Rizzo (caterina.rizzo@iss.it)Ivory Coast: Herve A. Kadjo (hervekadjo@pasteur.ci)Kazakhstan: Gulzhan Muratbayeva (hnv2@cdc.gov)Kenya: Joshua Mott (zud9@cdc.gov)Madagascar: Jean-Michel Heraud (jmheraud@pasteur.mg)Morocco: Amal Barakat (amal.barakat@yahoo.fr)New Zealand: Sue Huang (sue.huang@esr.cri.nz)Nicaragua: Alexey W. Clara (wclara@cdc.gov)Panama: Alexey W. Clara (wclara@cdc.gov)Portugal: Ana Paula Rodrigues (ana.rodrigues@insa.min-saude.pt)Singapore: Vernon Lee (vernonljm@hotmail.com)South Africa: Cheryl Cohen (cherylc@nicd.ac.za)Turkey: Meral Akcay Ciblak (ciblakm@yahoo.com)Ukraine: Alla Mironenko (miralla@ukr.net)Viet Nam: Le Thi Quinh Mai (lom9@hotmail.com); International audience; BACKGROUND:Influenza disease burden varies by age and this has important public health implications. We compared the proportional distribution of different influenza virus types within age strata using surveillance data from twenty-nine countries during 1999-2014 (N=358,796 influenza cases).METHODS:For each virus, we calculated a Relative Illness Ratio (defined as the ratio of the percentage of cases in an age group to the percentage of the country population in the same age group) for young children (0-4 years), older children (5-17 years), young adults (18-39 years), older adults (40-64 years), and the elderly (65+ years). We used random-effects meta-analysis models to obtain summary relative illness ratios (sRIRs), and conducted meta-regression and sub-group analyses to explore causes of between-estimates heterogeneity.RESULTS:The influenza virus with highest sRIR was A(H1N1) for young children, B for older children, A(H1N1)pdm2009 for adults, and (A(H3N2) for the elderly. As expected, considering the diverse nature of the national surveillance datasets included in our analysis, between-estimates heterogeneity was high (I2>90%) for most sRIRs. The variations of countries' geographic, demographic and economic characteristics and the proportion of outpatients among reported influenza cases explained only part of the heterogeneity, suggesting that multiple factors were at play.CONCLUSIONS:These results highlight the importance of presenting burden of disease estimates by age group and virus (sub)type.

Objective Between February 2012 and May 2016, six residents of an 11-storey apartment block were diagnosed with MDR-TB. Based on initial tests, all isolates had similar genotypic profiles, although there were no identifiable epidemiological transmission patterns between three cases. We present findings from the cluster investigation and results of a mass screening exercise. Design Free voluntary TB screening was offered to past and current residents of the apartment block, comprising an interview, Chest X-Ray, and Interferon Gamma Release Assay or Tuberculin skin test. Expected latent TB proportions were calculated using a reference population, and whole genome sequencing (WGS) was performed. Results The index case was involved in a separate gaming centre outbreak involving five patrons. 241 current (67.9% of 355 residents) and 18 past residents were screened. The latent TB proportion was 19.9%, which was at the higher end of the expected range. WGS confirmed relatedness of cases' MDR-TB isolates– eight of 10 isolates were genetically identical, while the remaining two were one Single Nucleotide Polymorphism apart. Conclusion With WGS, TB clusters not apparent through regular activity-based contact tracing may be detected. Mass screening may help inform the extent of transmission, but is limited by participation and difficulties in interpretation.

From 2014 to 2017, the World Health Organization convened a working group to evaluate influenza disease burden and vaccine efficacy to inform estimates of maternal influenza immunization program impact. The group evaluated existing systematic reviews and relevant primary studies, and conducted four new systematic reviews. There was strong evidence that maternal influenza immunization prevented influenza illness in pregnant women and their infants, although data on severe illness prevention were lacking. The limited number of studies reporting influenza incidence in pregnant women and infants under six months had highly variable estimates and underrepresented low- and middle-income countries. The evidence that maternal influenza immunization reduces the risk of adverse birth outcomes was conflicting, and many observational studies were subject to substantial bias. The lack of scientific clarity regarding disease burden or magnitude of vaccine efficacy against severe illness poses challenges for robust estimation of the potential impact of maternal influenza immunization programs.KeywordsInfluenzaImmunizationPregnancyInfants

We assessed and found cross-protection between the influenza pandemic and 2 seasonal viruses that circulated in Singapore. Age-related differences in disease severity between the subtypes were investigated, and we demonstrate birth cohort effects consistent with the theory of antigenic sin., Background After 2009, pandemic influenza A(H1N1) [A(H1N1)pdm09] cocirculated with A(H3N2) and B in Singapore. Methods A cohort of 760 participants contributed demographic data and up to 4 blood samples each from October 2009 to September 2010. We compared epidemiology of the 3 subtypes and investigated evidence for heterotypic immunity through multivariable logistic regression using a generalized estimating equation. To examine age-related differences in severity between subtypes, we used LOESS (locally weighted smoothing) plots of hospitalization to infection ratios and explored birth cohort effects referencing the pandemic years (1957; 1968). Results Having more household members aged 5–19 years and frequent public transport use increased risk of infection, while preexisting antibodies against the same subtype (odds ratio [OR], 0.61; P = .002) and previous influenza infection against heterotypic infections (OR, 0.32; P = .045) were protective. A(H1N1)pdm09 severity peaked in those born around 1957, while A(H3N2) severity was least in the youngest individuals and increased until it surpassed A(H1N1)pdm09 in those born in 1952 or earlier. Further analysis showed that severity of A(H1N1)pdm09 was less than that for A(H3N2) in those born in 1956 or earlier (P = .021) and vice versa for those born in 1968 or later (P < .001), with no difference in those born between 1957 and 1967 (P = .632). Conclusions Our findings suggest that childhood exposures had long-term impact on immune responses consistent with the theory of antigenic sin. This, plus observations on short-term cross-protection, have implications for vaccination and influenza epidemic and pandemic mitigation strategies.

Introduction Achieving UNAIDS 90‐90‐90 targets is a crucial step towards ending the AIDS epidemic. Many countries have published estimates of care cascades, although often with methodological limitations. We describe an approach that used the national HIV registry as a starting‐point to determine the HIV care cascade and resulting UNAIDS 90‐90‐90 estimates for Singapore in 2014. Methods HIV is a legally notifiable disease in Singapore. The anonymized HIV registry data provided for a back‐calculation model from the European Centre for Disease Prevention and Control to obtain 2014 estimates for the total number of persons living with HIV (PLHIV), and the count in the registry for proportions diagnosed with HIV and linked to care. Using additional data collected for a simple random sample from the registry, outcomes in 2015 and 2016 were ascertained retrospectively to derive proportions for those retained in care, on antiretroviral therapy, and achieved viral suppression. Findings were extrapolated to derive national estimates and UN90‐90‐90 estimates. Bootstrapped samples from the model and sample were used to derive 95% confidence intervals. Results An estimated 6900 (95% CI 6650, 7050) persons were living with HIV and AIDS in 2014. Of these, 4948 were diagnosed with HIV, and 4820 had been linked to care. The random sample of 500 persons was further analysed, and of these, 87.2% were retained in care, 84.6% on antiretroviral therapy, and 79.6% had suppressed viral loads. The proportions of HIV‐infected individuals on antiretroviral therapy and achieving viral suppression were 60.7% (95% CI 58.4, 63.6) and 57.1% (95% CI 55.0, 60.5) respectively. The corresponding UNAIDS 90‐90‐90 estimates were 71.7% (95% CI 70.0, 74.2) of all persons diagnosed; 84.6% (95% CI 81.6, 87.4) of diagnosed persons being on antiretroviral therapy, and 94.1% (95% CI 91.6, 96.2) of persons on therapy having achieved viral suppression. Conclusions A national HIV registry, alongside back‐calculation and additional data from a sample, can be used to estimate attainment of UNAIDS 90‐90‐90 targets and identify system gaps. The registry had advantages of providing a well‐established, comprehensive capture of diagnosed persons and easily accessible data. The same approach can be used elsewhere if similar data are available.

Background We previously estimated Singapore's influenza‐associated hospitalisation rate for pneumonia and influenza (P&I) in 2010‐2012 to be 29.6 per 100 000 person‐years, which corresponds to 11.2% of all P&I hospitalisations. Objectives This study aims to update Singapore's estimates of the influenza‐associated pneumonia and influenza (P&I) hospitalisation burden using the latest data from 2010 to 2017. Methods We estimated the number of P&I hospitalisations associated with influenza using generalised additive models. We specified the weekly number of admissions for P&I and the weekly influenza positivity in the models, along with potential confounders such as weekly respiratory syncytial virus (RSV) positivity and meteorological data. Results In 2010‐2017, 16.3% of all P&I hospitalisations in Singapore were estimated to be attributed to influenza, corresponding to an excess influenza‐associated P&I hospitalisation rate of 50.1 per 100 000 person‐years. Higher excess rates were estimated for children aged 0‐4 years (186.8 per 100 000 person‐years) and elderly aged ≥ 65 years (338.0 per 100 000 person‐years). Higher influenza‐associated hospitalisation rates were estimated for 2016 and 2017 (67.9 and 75.1 per 100 000 persons, respectively) years when the influenza A(H3N2) subtype was dominant. Conclusion Influenza burden in Singapore has increased since 2010. Influenza vaccination programmes should continue to be prioritised for the young and the elderly.

Background Few studies have evaluated the relative cross-protection conferred by infection with different groups of viruses through studies of sequential infections in humans. We investigated the presence of short-lived relative cross-protection conferred by specific prior viral infections against subsequent febrile respiratory illness (FRI). Methods Men enlisted in basic military training between December 2009 and December 2014 were recruited, with the first FRI as the study entry point. ResPlex II assays and real-time polymerase chain reaction assays were used to detect viral pathogens in nasal wash samples, and survival analyses were performed to determine whether infection with particular viruses conferred short-lived relative cross-protection against FRI. Results Prior infection with adenovirus (hazard ratio [HR], 0.24; 95% confidence interval [CI], .14–.44) or influenza virus (HR, 0.52; 95% CI, .38–.73) conferred relative protection against subsequent FRI episode. Results were statistically significant even after adjustment for the interval between enlistment and FRI (P < .001). Adenovirus-positive participants with FRI episodes tended to be protected against subsequent infection with adenovirus, coronavirus, enterovirus/rhinovirus, and influenza virus (P = .062–.093), while men with influenza virus–positive FRI episodes tended be protected against subsequent infection with adenovirus (P = .044) and influenza virus (P = .081). Conclusion Prior adenovirus or influenza virus infection conferred cross-protection against subsequent FRI episodes relative to prior infection due to other circulating viruses.

Plasmodium knowlesi is a simian malaria parasite currently recognized as the fifth causative agent of human malaria. Recently, naturally acquired P. cynomolgi infection in humans was also detected in Southeast Asia. The main reservoir of both parasites is the long-tailed and pig-tailed macaques, which are indigenous in this region. Due to increased urbanization and changes in land use, there has been greater proximity and interaction between the long-tailed macaques and the general population in Singapore. As such, this study aims to determine the prevalence of simian malaria parasites in local macaques to assess the risk of zoonosis to the general human population. Screening for the presence of malaria parasites was conducted on blood samples from 660 peridomestic macaques collected between Jan 2008 and Mar 2017, and 379 wild macaques collected between Mar 2009 and Mar 2017, using a Pan-Plasmodium-genus specific PCR. Positive samples were then screened using a simian Plasmodium species-specific nested PCR assay to identify the species of parasites (P. knowlesi, P. coatneyi, P. fieldi, P. cynomolgi, and P. inui) present. All the peridomestic macaques sampled were tested negative for malaria, while 80.5% of the 379 wild macaques were infected. All five simian Plasmodium species were detected; P. cynomolgi being the most prevalent (71.5%), followed by P. knowlesi (47.5%), P. inui (42.0%), P. fieldi (32.5%), and P. coatneyi (28.5%). Co-infection with multiple species of Plasmodium parasites was also observed. The study revealed that Singapore’s wild long-tailed macaques are natural hosts of the five simian malaria parasite species, while no malaria was detected in all peridomestic macaques tested. Therefore, the risk of simian malaria transmission to the general human population is concluded to be low. However, this can be better demonstrated with the incrimination of the vectors of simian malaria parasites in Singapore., Author summary Malaria is one of the most important vector-borne diseases in the world. In Southeast Asia, the incidence of human malaria infections caused by simian malaria parasites that originate from macaques has been increasing in the last decade, possibly due to closer proximity between the macaque and human population as a result of deforestation. In Singapore, urbanization and change in land use have resulted in closer proximity and interactions between macaques and the general human population. In order to assess the risk of potential simian malaria zoonosis, 1039 macaques’ blood samples were screened in this study for simian malaria parasites. Our results showed that simian malaria parasites were only detected in macaques living deep in the forest within the military protected zone, while macaques living close to human habitations are malaria-free. This study illustrated a low risk of zoonotic transmission of simian malaria parasites to the general population in Singapore.

Singapore has experienced periodic dengue epidemics despite maintaining a low Aedes house index. Each epidemic was associated with a switch in the predominant serotype. We investigated the temporal dynamics of dengue fever and dengue virus (DENV) and analyzed the epidemiological and entomological patterns of dengue in Singapore from 2004 to 2016. The case surveillance is based on a mandatory notification system that requires all medical practitioners to report clinically suspected and laboratory-confirmed cases. Circulating (DENV) serotypes are monitored through a virus surveillance program. Entomological surveillance involves inspections for larval breeding and monitoring of adults using gravitraps. Singapore experienced a similar epidemic pattern during 2004–2007 and 2013–2016. The pattern involved a 2-year DENV-1 epidemic occurring after a switch in the predominant serotype from DENV-2 to DENV-1, followed by a “lull” year. Thereafter, the predominant serotype switched back to DENV-2, tailed by a small-scale epidemic. Across the years, the highest incidence group was in the 25–44 years age group. The incidence rate of those aged ≥ 55 years was about half of that of the 15–24 years age group during DENV-1 predominant years. However, it was almost equal to the younger age group in DENV-2 predominant years. Types of Aedes aegypti breeding habitats remained similar. Dengue incidence was significantly higher in areas with high breeding percentage (BP) than areas with low BP (P < 0.05). In conclusion, the oscillation of DENV-1 and DENV-2, throughout the 13-year period, led to a cyclical epidemic pattern and older adults were more affected by DENV-2 than DENV-1. Published version

Objectives We determined the seroprevalence of chikungunya virus (CHIKV) infection in the adult resident population in Singapore following local outbreaks of chikungunya fever (CHIKF) in 2008–2009. Methods Our cross-sectional study involved residual sera from 3,293 adults aged 18–79 years who had participated in the National Health Survey in 2010. Sera were tested for IgG antibodies against CHIKV and dengue virus (DENV) and neutralizing antibodies against CHIKV. Results The prevalence of CHIKV-neutralizing antibodies among Singapore residents aged 18–79 years was 1.9% (95% confidence interval: 1.4%– 2.3%). The CHIKV seroprevalence was highest in the elderly aged 70–79 years at 11.5%, followed by those aged 30–39 years at 3.1%. Men had significantly higher CHIKV seroprevalence than women (2.5% versus 1.3%, p = 0.01). Among the three main ethnic groups, Indians had the highest seroprevalence (3.5%) compared to Chinese (1.6%) and Malays (0.7%) (p = 0.02 and p = 0.01, respectively). Multivariable logistic regression identified adults aged 30–39 years and 70–79 years, men, those of Indian ethnicity and ethnic minority groups, and residence on ground floor of public and private housing apartments as factors that were significantly associated with a higher likelihood of exposure to CHIKV. The overall prevalence of anti-DENV IgG antibodies was 56.8% (95% CI: 55.1%– 58.5%), while 1.5% (95% CI: 1.1%– 2.0%) of adults possessed both neutralizing antibodies against CHIKV and IgG antibodies against DENV. Conclusions Singapore remains highly susceptible to CHIKV infection. There is a need to maintain a high degree of vigilance through disease surveillance and vector control. Findings from such serological study, when conducted on a regular periodic basis, could supplement surveillance to provide insights on CHIKV circulation in at-risk population., Author summary The prevalence of neutralizing antibodies against chikungunya virus (CHIKV) was low at 1.9% among resident adults in Singapore after local outbreaks in 2008–2009. Adults aged 30–39 years and 70–79 years, men, those of Indian ethnicity and ethnic minority groups, and residence on ground floor of public and private housing apartments were significantly associated with a higher likelihood of exposure to CHIKV.

During November 2012–July 2013, a marked increase of adenovirus type 7 (Ad7) infections associated with severe disease was documented among pediatric patients in Singapore. Phylogenetic analysis revealed close genetic links with severe Ad7 outbreaks in China, Taiwan, and other parts of Asia. Published version

Background From 31 August to 9 September 2015, a total of 150 military personnel at a military institution in Singapore were infected with acute gastroenteritis (AGE) with an attack rate of approximately 3%. This study aimed to determine the epidemiology of the outbreak, investigate its origins, and discuss measures to prevent future occurrences. Methods After the AGE outbreak was declared on 31 August 2015, symptom surveys, hygiene inspections, and the testing of water, food, and stool samples were initiated. We collected 86 stool samples from AGE cases and 58 samples from food-handlers during the course of the outbreak and these stool samples were tested for 8 bacterial pathogens and 2 viral pathogens (i.e., norovirus and sapovirus). Results We detected Sapovirus (SaV), group I Norovirus (NoV GI) and group II Norovirus (NoV GII) from the stool samples of AGE cases. Further sequence analyses showed that the AGE outbreak in August was caused mainly by three rarely reported calicivirus novel genotypes: NoV GI.7, NoV GII.17 and SaV GII.3. Control measures implemented focused on the escalation of personal and environmental hygiene, which included the separation of affected and unaffected soldiers, enforcement of rigorous hand-washing and hygiene, raising awareness of food and water safety, and disinfection of communal areas with bleach. Conclusions This study identified both NoV and SaV as the causative agents for an AGE outbreak at a Singapore military camp in August 2015. This study is also the first to report SaV as one of the main causative agents, highlighting the importance of caliciviruses as causative agents of AGE outbreaks in the Singapore military. As there are no commercially available vaccines against caliciviruses, strict personal hygiene and proper disinfection of environmental surfaces remain crucial to prevent calicivirus outbreak and transmission.

Background Respiratory illnesses have been identified as a significant factor leading to lost training time and morbidity among Singapore military recruits. A surveillance programme has been put in place to determine etiological agents responsible for febrile, as well as afebrile respiratory illnesses in a military camp. The goal of the study is to better understand the epidemiology of these diseases and identify potential countermeasures to protect military recruits against them. Methods From Jan 2016 - Jan 2017, a total of 2647 respiratory cases were enrolled into the surveillance programme. The cases were further stratified into Febrile Respiratory Illness (FRI, with body temperature > 37.5 °C) or Acute Respiratory Illness (ARI, with body temperature

Free PMC article: https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/31513690/ We describe the epidemiological characteristics, pattern of circulation, and geographical distribution of influenza B viruses and its lineages using data from the Global Influenza B Study. We included over 1.8 million influenza cases occurred in thirty-one countries during 2000-2018. We calculated the proportion of cases caused by influenza B and its lineages; determined the timing of influenza A and B epidemics; compared the age distribution of B/Victoria and B/Yamagata cases; and evaluated the frequency of lineage-level mismatch for the trivalent vaccine. The median proportion of influenza cases caused by influenza B virus was 23.4%, with a tendency (borderline statistical significance, p = 0.060) to be higher in tropical vs. temperate countries. Influenza B was the dominant virus type in about one every seven seasons. In temperate countries, influenza B epidemics occurred on average three weeks later than influenza A epidemics; no consistent pattern emerged in the tropics. The two B lineages caused a comparable proportion of influenza B cases globally, however the B/Yamagata was more frequent in temperate countries, and the B/Victoria in the tropics (p = 0.048). B/Yamagata patients were significantly older than B/Victoria patients in almost all countries. A lineage-level vaccine mismatch was observed in over 40% of seasons in temperate countries and in 30% of seasons in the tropics. The type B virus caused a substantial proportion of influenza infections globally in the 21st century, and its two virus lineages differed in terms of age and geographical distribution of patients. These findings will help inform health policy decisions aiming to reduce disease burden associated with seasonal influenza. info:eu-repo/semantics/publishedVersion

Introduction Previous influenza pandemics had second and on occasion third waves in many countries that were at times more severe than the initial pandemic waves. Objective This study aims to determine the seroepidemiology of successive waves of H1N1pdm09 infections in Singapore and the overall risks of infection. Methods We performed a cohort study amongst 838 adults, with blood samples provided upon recruitment and at 5 points from 2009 to 2011 and tested by haemagglutination inhibition (HI) with A/California/7/2009 (H1N1pdm09). Surveys on key demographic and clinical information were conducted at regular intervals, and associations between seroconversion and these variables were investigated. Results After the initial wave from June to September 2009, second and third waves occurred from November 2009 to February 2010 and April to June 2010, respectively. Seroconversion was 13·5% during the first wave and decreased to 6·2% and 6·8% in subsequent waves. Across the three waves, the elderly and those with higher starting HI titres were at lower risk of seroconversion, while those with larger households were at greater risk. Those with higher starting HI titres were also less likely to have an acute respiratory infection. Conclusions The second and third waves in Singapore had lower serological attack rates than the first wave. The elderly and those with higher HI titres had lower risk, while those in larger households had higher risk of seroconversion.