Riding high: seroprevalence of SARS-CoV-2 after 4 pandemic waves in Manitoba, Canada, April 2020-February 2022.

BACKGROUND: Canada is emerging from the largest SARS-CoV-2 Omicron wave to date, with over 3.3 million confirmed cases. Unfortunately, PCR confirmed cases illuminate only a small portion of infections in the community and underestimate true disease burden. Population based seroprevalence studies, which measure antibody levels against a virus can more accurately estimate infection rates in the community and identify geographical and epidemiological trends to inform public health responses. METHODS: The Manitoba COVID-19 Seroprevalence (MCS) study is a population-based cross-sectional study to assess the prevalence of SARS-CoV-2 antibodies across the province. Residual convenience specimens (n = 14,901) were tested for anti-SARS-CoV-2 nucleocapsid and spike IgG antibodies from April 1, 2020 to February 31, 2022. We estimated the monthly and cumulative prevalence using an exponential decay model, accounting for population demographics, sensitivity/specificity, and antibody waning. This approach generated estimates of natural infection as well as total antibody including vaccine-induced immunity within the community. FINDINGS: After four waves of the pandemic, 60.1% (95%CI-56.6-63.7) of Manitobans have generated SARS-CoV-2 antibodies due to natural exposure independent of vaccination. Geographical analysis indicates a large portion of provincial prevalence stems from increased transmission in the Northern (92.3%) and Southern (71.8%) regional health authorities. Despite the high mortality rates reported by Manitoba, infection fatality ratios (IFR) peaked at 0.67% and declined to 0.20% following the Omicron wave, indicating parity with other national and international jurisdictions. Manitoba has achieved 93.4% (95%CI- 91.5-95.1) total antibody when including vaccination. INTERPRETATION: Our data shows that more than 3 in 5 Manitobans have been infected by SARS-CoV-2 after four waves of the pandemic. This study also identifies key geographical and age specific prevalence rates that have contributed greatly to the overall severity of the pandemic in Manitoba and will inform jurisdictions considering reduction of public health measures.

Evaluation of commercial SARS-CoV-2 serological assays in Canadian public health laboratories.

The COVID-19 pandemic has led to the influx of immunoassays for the detection of antibodies towards severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into the global market. The Canadian Public Health Laboratory Network Serology Task Force undertook a nationwide evaluation of twelve laboratory and 6 point-of-care based commercial serological assays for the detection of SARS-CoV-2 antibodies. We determined that there was considerable variability in the performance of individual tests and that an orthogonal testing algorithm should be prioritized to maximize the accuracy and comparability of results across the country. The manual enzyme immunoassays and point-of-care tests evaluated had lower specificity and increased coefficients of variation compared to automated enzyme immunoassays platforms putting into question their utility for large-scale sero-surveillance. Overall, the data presented here provide a comprehensive approach for applying accurate serological assays for longitudinal sero-surveillance and vaccine trials while informing Canadian public health policy.

Evaluation of the Diasorin Liaison® XL Zika Capture IgM CMIA for Zika virus serological testing.

Due to the increase of Zika virus (ZIKV) transmission throughout the world, many commercial kits have recently become available to aid in laboratory diagnosis of ZIKV infections in clinical samples. Here, we analyze the fully automated Liaison® XL Zika Capture immunoglobulin M (IgM) assay against the recommended IgM-capture enzyme-linked immunosorbent assay.

Human seroprevalence of Borrelia miyamotoi in Manitoba, Canada, in 2011-2014: a cross-sectional study.

BACKGROUND: Hard tick-borne relapsing fever caused by Borrelia miyamotoi has been reported in Russia, the Netherlands, Germany, Japan and the northeastern and upper midwestern United States. We sought to investigate the presence of B. miyamotoi infection in humans in Manitoba, Canada. METHODS: Two hundred fifty sera collected from residents of Manitoba with suspected Lyme disease between 2011 and 2014 were tested for Borrelia burgdorferi antibody using a C6 peptide enzyme-linked immunosorbent assay (ELISA) followed by Western blot. Residual sera were then anonymized, stored at -80°C and subsequently thawed and tested for B. miyamotoi antibody using a 2-step glycerosphosphodiester phosphodiesterase-based ELISA and Western blot assay. RESULTS: Twenty-four of the 250 (9.6%) sera tested positive for B. miyamotoi immunoglobulin G. Participants who were B. miyamotoi seropositive were predominantly male (54%) and younger on average than those who were seronegative (32 and 44 yr of age, respectively). Participants who were seropositive for B. burgdorferi were significantly more likely to be B. miyamotoi seropositive than those who were B. burgdorferi seronegative (20.3% v. 6.6%, respectively, odds ratio 3.6, 95% confidence interval 1.5-8.5). INTERPRETATION: This initial report of human B. miyamotoi infection in Canada should raise awareness of hard tick-borne relapsing fever among clinicians and residents of areas in Canada and western North America where Lyme disease is endemic.

Evaluation of a commercially available Zika virus IgM ELISA: specificity in focus.

Zika virus (ZIKV), an emerging arbovirus, has become the center of attention since it was linked to congenital abnormalities. Given the overlapping clinical picture of ZIKV disease with other infectious diseases and as an exigent public health matter, timely and reliable diagnosis of ZIKV infection is crucial. We evaluated the performance of a commercially available NS1-based ZIKV IgM ELISA. Our results showed suboptimal sensitivity within the first 5 days after onset while specificity remained robust.

Retrospective Study Investigating the Seroprevalence of Anaplasma phagocytophilum in Manitoba, Canada: 2011-2014.

Human granulocytic anaplasmosis is currently not nationally notifiable in Canada. This for the most part accounts for gross under-estimation of true incidence and prevalence of HGA and would potentially culminate in clinical missed opportunities. To the best of our knowledge, this is the first report on the seroprevalence of Anaplasma phagocytophilum in a Canadian jurisdiction with known established black-legged tick populations.

Retrospective study of the prevalence and clinical significance of hepatitis B virus precore and basal core promoter variants.

BACKGROUND: Hepatitis B virus (HBV) precore (PC) and basal core promoter (BCP) variants are well known; however, their prevalence in North America is unclear, especially among hepatitis B e antigen-negative patients. OBJECTIVE: To investigate the prevalence of PC/BCP mutations and their clinical significance. METHODS: One hundred twenty-eight patients positive for both hepatitis B surface antigen and hepatitis B e antibody were selected, and PC/BCP mutations were identified using a line probe assay. The subjects' charts were reviewed for race/ethnicity, HBV genotype, HBV viral load, sex, liver enzyme levels, imaging and biopsy results up to 10 years before the study. RESULTS: The prevalence of PC and BCP variants were 47.6% and 62.5%, respectively. Older age was associated with aspartate aminotransferase-to-platelet index ratio (APRI) ≥0.7 (P=0.011) and abnormal imaging/biopsy results (P=0.0008). Although the presence of BCP variant(s) was associated with APRI ≥0.7 (P=0.029), it was not associated with abnormal imaging/biopsy results. The combination of age ≥50 years and the presence of BCP variant(s) was associated with abnormal imaging/biopsy results, suggestive of either cirrhosis or hepatocellular carcinoma (not observed with PC mutation). Neither sex or genotype, or median HBV viral load showed significant influence on any of these outcomes. CONCLUSIONS: The present study suggests that the prevalence of PC and BCP mutations are higher than what has been previously reported. One potential explanation would be increased immigration in the past decade. Considering the potential public health and clinical implications of these variants, long-term multicentre and prospective studies could further unravel the uncertainty around these variants.