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We aimed to determine population immunity to measles in Canada, and to assess the risk of future outbreaks. We tested 11,176 sera from Cycles 2 (2009-2011) and 3 (2011-2013) cohorts from the biobank of Statistics Canada's Canadian Health Measures Survey (CHMS) using the BioPlex 2220 MMRV IgG assay. We then tested all BioPlex negative and equivocal samples using a more sensitive Plaque Reduction Neutralization Test (PRNT). We determined the weighted proportion of positive, equivocal, and negative samples by age, sex, region and whether individuals were born in Canada. We found that 90.0% (95% confidence interval (CI): 88.2, 91.9) of samples were positive, 4.5% (95% CI: 3.4, 5.5) were equivocal and 5.5% (95% CI: 4.3, 6.7) were negative. Individuals in the 12-19 year age band had the lowest proportion positive at 78.7% (95% CI: 74.2, 83.2) and the highest proportion of positive samples was found in those 60-79 years (99.6%, 95% CI: 99.3, 99.9). Seropositivity was consistently90% across a broad range of pediatric and adult age bands (6-39 years). We found that a slightly higher proportion of females were positive (91.9%, 95% CI: 90.1, 93.6) compared to males (88.3%, 95% CI: 85.8, 90.7). When taking into account interaction between age and born in Canada status, we found individuals born in Canada aged 19 and under were less susceptible (OR = 0.6 (95% CI: 0.4, 0.95)) compared to those born outside Canada whereas, those aged 20 and over were more susceptible (OR = 1.7 (95% CI: 1.1, 2.8)). Our findings indicate that measles immunity in Canada is below the 95% immunity threshold required to sustain measles elimination, underscoring the importance of maintaining high vaccine coverage to prevent future measles outbreaks and sustain Canada's elimination status.

Background Within-household transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been identified as one of the main sources of spread of coronavirus disease 2019 (COVID-19) after lockdown restrictions and self-isolation guidelines are implemented. Secondary attack rates among household contacts are estimated to be 5–10 times higher than among non-household contacts, but it is unclear which individuals are more prone to transmit infection within their households. Methods Using address matching, a cohort was assembled of all individuals with laboratory-confirmed COVID-19 residing in private households in Ontario, Canada. Descriptive analyses were performed to compare characteristics of cases in households that experienced secondary transmission versus those that did not. Logistic regression models were fit to determine index case characteristics and neighborhood characteristics associated with transmission. Results Between January and July 2020, there were 26 714 individuals with COVID-19 residing in 21 226 households. Longer testing delays (≥5 vs 0 days; odds ratio [OR], 3.02; 95% confidence interval [CI], 2.53–3.60) and male gender (OR, 1.28; 95% CI, 1.18–1.38) were associated with greater odds of household secondary transmission, while being a healthcare worker (OR, .56; 95% CI, .50–.62) was associated with lower odds of transmission. Neighborhoods with larger average family size and a higher proportion of households with multiple persons per room were also associated with greater odds of transmission. Conclusions It is important for individuals to get tested for SARS-CoV-2 infection as soon as symptoms appear, and to isolate away from household contacts; this is particularly important in neighborhoods with large family sizes and/or crowded households.

Background Serosurveys for SARS-CoV-2 aim to estimate the proportion of the population that has been infected. Aim This observational study assesses the seroprevalence of SARS-CoV-2 antibodies in Ontario, Canada during the first pandemic wave. Methods Using an orthogonal approach, we tested 8,902 residual specimens from the Public Health Ontario laboratory over three time periods during March–June 2020 and stratified results by age group, sex and region. We adjusted for antibody test sensitivity/specificity and compared with reported PCR-confirmed COVID-19 cases. Results Adjusted seroprevalence was 0.5% (95% confidence interval (CI): 0.1–1.5) from 27 March–30 April, 1.5% (95% CI: 0.7–2.2) from 26–31 May, and 1.1% (95% CI: 0.8–1.3) from 5–30 June 2020. Adjusted estimates were highest in individuals aged ≥ 60 years in March–April (1.3%; 95% CI: 0.2–4.6), in those aged 20–59 years in May (2.1%; 95% CI: 0.8–3.4) and in those aged ≥ 60 years in June (1.6%; 95% CI: 1.1–2.1). Regional seroprevalence varied, and was highest for Toronto in March–April (0.9%; 95% CI: 0.1–3.1), for Toronto in May (3.2%; 95% CI: 1.0–5.3) and for Toronto (1.5%; 95% CI: 0.9–2.1) and Central East in June (1.5%; 95% CI: 1.0–2.0). We estimate that COVID-19 cases detected by PCR in Ontario underestimated SARS-CoV-2 infections by a factor of 4.9. Conclusions Our results indicate low population seroprevalence in Ontario, suggesting that public health measures were effective at limiting the spread of SARS-CoV-2 during the first pandemic wave.

BackgroundMinimizing delays in disease identification and reporting improves the timeliness of surveillance data, and can reduce transmission of COVID-19. Our study investigates factors associated with timely testing and reporting of COVID-19 during the first pandemic wave in one province of Canada.MethodsWe identified all persons with confirmed SARS-CoV-2 infection residing in private households across the largest province of Canada, Ontario from the date of the first confirmed case in Ontario (January 25) to July 19, 2020. Our primary outcomes consisted of: (1) specimen collection within 1 day of symptom onset (test seeking), (2) test result reported to local public health within 1 day of specimen collection (test turnaround), and (3) entry of case data into the provincial database within 1 day of reporting test results (reporting). We examined 14 covariates including eight case characteristics, and six neighborhood characteristics. In addition to descriptive measures, logistic regression models were fitted. Unadjusted models included the covariate alone, while adjusted models included age, gender, month, and region.FindingsAmong 27,198 COVID-19 cases from January 25 2020 to July 19 2020, 28·7% had timely test seeking, 40·2% had timely test turnaround, and 75·5% had timely reporting. Male gender had lower odds of timely test seeking (adjusted odds ratio [aOR] 0·79 [95% CI: 0·74-0·85]) compared to females. Healthcare worker status (aOR 2·77 [95% CI: 2·52-3·05] compared to non-healthcare workers), and age ≥80 years (aOR 1·59 [95% CI: 1·33-1·91] compared to 40-59 year olds) were associated with timely test seeking. Specimen collection on Fridays and Saturdays (aOR 0·88 [95% CI: 0·79-0·98], aOR 0·83 [95% CI: 0·74-0·92] respectively, compared to Wednesdays) had lower odds of timely test turnaround. Urban areas (aOR 1·55 [95% CI: 1·41-1·70] compared to rural areas) were associated with timely test turnaround. Urban areas (aOR 0·79 [95% CI: 0·70-0·89] compared to rural areas) were less likely to have timely reporting.InterpretationIndividual, neighborhood, and administrative factors are associated with timely testing and reporting of SARS-CoV-2 infections. These findings present considerations for developing targeted strategies to minimize delays and improve timely testing and reporting of SARS-CoV-2 infections.FundingThis study was funded by Public Health Ontario.Research in ContextEvidence before this studyWe searched PubMed and medRxiv up to November 30 2020 to identify studies examining the impact of delays in the disease reporting process on the public health response to COVID-19. We used the search terms (“2019-nCoV” OR “COVID-19” OR “SARS-CoV-2”) AND (“delays” OR “timely” OR “reporting” OR “test” OR “turnaround”), and reviewed reference lists of any relevant articles in the original search. Numerous modeling studies have highlighted the importance of timely testing and reporting to effectively control the spread of COVID-19. Additional studies have also identified delays of only 1 day in testing were associated with increased risk of secondary transmission within households. However no study has described the multiple delays in the disease reporting process of COVID-19 and examined factors associated with timely disease reporting using a large population cohort.Added value of this studyOur study described timely test seeking, test turnaround, and reporting for laboratory-confirmed COVID-19 cases in Ontario, Canada and identified associated individual, neighbourhood, and administrative factors. To the best of our knowledge, this study is the first to describe detailed delays in the disease reporting process of COVID-19 and identified associated factors using a large population cohort.Implications of all the available evidenceNumerous individual, neighborhood, and administrative characteristics are associated with timely testing and reporting of COVID-19. These identified factors may be used to develop strategies such as broadened test access, prioritization of vulnerable populations, and increased testing capacity to reduce delays in testing and reporting and improve the effectiveness of public health response to COVID-19.

BACKGROUNDWithin-household transmission of SARS-CoV-2 infection has been identified as one of the main sources of spread of COVID-19 after lockdown restrictions and self-isolation guidelines are implemented. Secondary attack rates among household contacts are estimated to be five to ten times higher than among non-household contacts, but it is unclear which individuals are more prone to transmit infection within their households.METHODSUsing address matching, a cohort was assembled of all laboratory-confirmed cases of COVID-19 residing in private households in Ontario, Canada. Descriptive analyses were performed to compare characteristics of cases in households that experienced secondary transmission versus those that did not. Logistic regression models were fit to determine index case characteristics and neighbourhood characteristics associated with transmission.FINDINGSBetween January and July, 2020, there were 26,152 cases of COVID-19 residing in 21,226 households. Longer testing delays (≥5 days versus 0 days OR=3·02, 95% CI: 2·53 - 3·60) and male sex (OR=1·28, 95% CI: 1·18 - 1·38) were associated with greater odds of household secondary transmission, while being a healthcare worker (OR=0·56, 95% CI: 0·50 - 0·62) was associated with lower odds of transmission. Neighbourhoods with larger average economic family size and a higher proportion of households with multiple persons per room were also associated with greater odds of transmission.INTERPRETATIONIt is important for individuals to get tested for SARS-CoV-2 infection as soon as symptoms appear, and to isolate away from household contacts; this is particularly important in neighbourhoods with large family sizes and/or crowded households.FUNDINGThis study was supported by Public Health Ontario.Research in ContextEVIDENCE BEFORE THIS STUDYWe searched PubMed and Google Scholar up to September 3, 2020 to identify individual-level cohort studies or meta-analyses on household transmission of COVID-19. We used the search terms (“COVID” OR “SARS-CoV-2”) AND (“household” [Title]), and also reviewed the reference lists of any studies found during the search to identify additional studies. We considered studies that reported secondary attack rates and/or other measures of association (i.e., relative risk, odds ratio, or hazard ratio) for household transmission. We did not consider any modelling studies, studies that focused specifically on children, or small case studies that included less than three households. The search returned 53 studies, of which 51 were included in three meta-analyses. Pooled household secondary attack rates from the three meta-analyses were 19%, 27%, and 30%; secondary attack rates in households were estimated to be five to ten times as high as in non-household settings. Most studies were conducted in Asia and identified households from contact tracing, with individual studies reporting on fewer than 6000 households. Most studies did not consider households with no secondary transmission, and focused on a limited set of secondary case characteristics.ADDED VALUE OF THIS STUDYWe applied an address matching algorithm, which identified 21,226 private households of laboratory-confirmed cases of COVID-19 in Ontario, Canada. Ontario has the advantage of a universal healthcare system and population-wide data for the entire province. To our knowledge, this study contains the largest number of private households with at least one confirmed case of COVID-19. We compared a variety of individual- and neighbourhood-level characteristics of households with and without secondary transmission. We also applied logistic regression models to determine index case characteristics associated with transmission, which gave important insights into factors that may help reduce secondary transmission in households.IMPLICATIONS OF ALL THE AVAILABLE EVIDENCEFindings from this study and existing evidence suggest that testing delays and household crowding play important roles in whether household secondary transmission occurs. Odds of household transmission may be reduced by cases seeking testing as soon as symptoms appear, and self-isolating outside the home or in a room alone if possible. These strategies may be considered by public health officials to reduce household transmission and mitigate local spread of COVID-19. Future research should further investigate the role of children and youth in household transmission.

Homeless people in the United States may experience poor hygiene and spend extended periods of time outdoors, which increases exposure to animal and insect vectors of disease. Despite these risks, efforts to understand frequency and risk factors for zoonotic and vector-borne infections among homeless people have been limited. We queried homeless people in Boston, Massachusetts (n=194) to evaluate exposure to urban wildlife and ectoparasites associated with infection. Thirty percent of participants reported seeing rodents daily, and 25% reported daily sightings of cats. Body lice and fleas were reported by 4% and 11% of participants, respectively. Sleeping outdoors and heavy drinking were positively associated with rodent and ectoparasite exposure. Frequent sightings of rodents and rodent feces among homeless people in particular areas may indicate human exposure risk to urban rodent-borne pathogens, including Leptospira spp, Seoul hantavirus, and Rickettsia akari. Epidemiologic studies of zoonotic and vector-borne infections in this population are warranted.

Drinking water is a recognized pathway through which populations can be exposed to biological and chemical hazards. We mapped Ontario Municipal Drinking Water Distribution systems (DWDS) by matchin...

Poster: "18th ICID / Fri_Station_03.2 / The role of regional surveillance networks in enhancing global outbreak reporting" by: "E. Joh1, L. Madoff2, Z. Haddad2, M. Carrion2, S. Mekaru3, M. Pollack2, B. Lassmann2; 1Toronto, ON/CA, 2Brookline/US, 3Boston/US"