Wastewater-Based Surveillance Is an Effective Tool for Trending COVID-19 Prevalence in Communities: A Study of 10 Major Communities for 17 Months in Alberta.

The correlations between SARS-CoV-2 RNA levels in wastewater from 12 wastewater treatment plants and new COVID-19 cases in the corresponding sewersheds of 10 communities were studied over 17 months. The analysis from the longest continuous surveillance reported to date revealed that SARS-CoV-2 RNA levels correlated well with temporal changes of COVID-19 cases in each community. The strongest correlation was found during the third wave (r = 0.97) based on the population-weighted SARS-CoV-2 RNA levels in wastewater. Different correlations were observed (r from 0.51 to 0.86) in various sizes of communities. The population in the sewershed had no observed effects on the strength of the correlation. Fluctuation of SARS-CoV-2 RNA levels in wastewater mirrored increases and decreases of COVID-19 cases in the corresponding community. Since the viral shedding to sewers from all infected individuals is included, wastewater-based surveillance provides an unbiased and no-discriminate estimation of the prevalence of COVID-19 compared with clinical testing that was subject to testing-seeking behaviors and policy changes. Wastewater-based surveillance on SARS-CoV-2 represents a temporal trend of COVID-19 disease burden and is an effective and supplementary monitoring when the number of COVID-19 cases reaches detectable thresholds of SARS-CoV-2 RNA in wastewater of treatment facilities serving various sizes of populations.

Wastewater-Based Surveillance Is an Effective Tool for Trending COVID-19 Prevalence in Communities: A Study of 10 Major Communities for 17 Months in Alberta

The correlations between SARS-CoV-2 RNA levels in wastewater from 12 wastewater treatment plants and new COVID-19 cases in the corresponding sewersheds of 10 communities were studied over 17 months. The analysis from the longest continuous surveillance reported to date revealed that SARS-CoV-2 RNA levels correlated well with temporal changes of COVID-19 cases in each community. The strongest correlation was found during the third wave (r = 0.97) based on the population-weighted SARS-CoV-2 RNA levels in wastewater. Different correlations were observed (r from 0.51 to 0.86) in various sizes of communities. The population in the sewershed had no observed effects on the strength of the correlation. Fluctuation of SARS-CoV-2 RNA levels in wastewater mirrored increases and decreases of COVID-19 cases in the corresponding community. Since the viral shedding to sewers from all infected individuals is included, wastewater-based surveillance provides an unbiased and no-discriminate estimation of the prevalence of COVID-19 compared with clinical testing that was subject to testing–seeking behaviors and policy changes. Wastewater-based surveillance on SARS-CoV-2 represents a temporal trend of COVID-19 disease burden and is an effective and supplementary monitoring when the number of COVID-19 cases reaches detectable thresholds of SARS-CoV-2 RNA in wastewater of treatment facilities serving various sizes of populations. Fluctuation of SARS-CoV-2 RNA levels in wastewater reflects temporal trends of new COVID-19 cases in the community correspondingly.

Seropositivity to SARS-CoV-2 in Alberta, Canada in a post-vaccination period (March 2021-July 2021).

BACKGROUND: The COVID-19 pandemic has necessitated the need to rapidly make public health decisions. We systematically evaluated SARS-CoV-2 seropositivity to understand local COVID-19 epidemiology and support evidence-based public health decision making. METHODS: Residual blood samples were collected for SARS-CoV-2 receptor binding domain (RBD) IgG testing over a 1-5 day period monthly from 26 February 2021-9 July 2021 from six clinical laboratories across the province of Alberta, Canada. Monthly crude and adjusted (for age and gender) seropositivity were calculated. Results were linked to provincial administrative, laboratory, and vaccine databases. RESULTS: 60,632 individual blood samples were tested. Vaccination data were available for 98.8% of samples. Adjusted RBD IgG positivity rose from 11.9% (95% confidence interval [CI] 11.9-12.0%) in March 2021 to 70.2% (95% CI 70.2-70.3%) in July 2021 (p < .0001). Seropositivity rose from 9.4% (95% CI 9.3-9.4%) in March 2021 to 20.2% (95% CI 20.1-20.2%) in July 2021 in unvaccinated Albertans. Unvaccinated seropositive individuals were from geographic areas with significantly (p < .001) lower median household income, lower proportion of married/common-law relationships, larger average household size and higher proportions of visible minorities compared to seronegative unvaccinated individuals. In July 2021, the age groups with the lowest and highest seropositivity in unvaccinated Albertans were those ≥80 years (12.0%, 95% CI 5.3-18.6%) and 20-29 years (24.2%, 95% CI 19.6-28.8%), respectively. Of seropositive unvaccinated individuals, 50.2% (95% CI 45.9-54.5%) had no record of prior SARS-CoV-2 molecular testing. CONCLUSIONS: Longitudinal surveillance of SARS-CoV-2 seropositivity with data linkage is valuable for decision-making during the pandemic.

Number of COVID-19 cases required in a population to detect SARS-CoV-2 RNA in wastewater in the province of Alberta, Canada: Sensitivity assessment.

With a unique and large size of testing results of 1,842 samples collected from 12 wastewater treatment plants (WWTP) for 14 months through from low to high prevalence of COVID-19, the sensitivity of RT-qPCR detection of SARS-CoV-2 RNA in wastewater that correspond to the communities was computed by using Probit analysis. This study determined the number of new COVID-19 cases per 100,000 population required to detect SARS-CoV-2 RNA in wastewater at defined probabilities and provided an evidence-based framework of wastewater-based epidemiology surveillance (WBE). Input data were positive and negative test results of SARS-CoV-2 RNA in wastewater samples and the corresponding new COVID-19 case rates per 100,000 population served by each WWTP. The analyses determined that RT-qPCR-based SARS-CoV-2 RNA detection threshold at 50%, 80% and 99% probability required a median of 8 (range: 4-19), 18 (9-43), and 38 (17-97) of new COVID-19 cases /100,000, respectively. Namely, the positive detection rate at 50%, 80% and 99% probability were 0.01%, 0.02%, and 0.04% averagely for new cases in the population. This study improves understanding of the performance of WBE SARS-CoV-2 RNA detection using the large datasets and prolonged study period. Estimated COVID-19 burden at a community level that would result in a positive detection of SARS-CoV-2 in wastewater is critical to support WBE application as a supplementary warning/monitoring system for COVID-19 prevention and control.

Pre-Vaccine Positivity of SARS-CoV-2 Antibodies in Alberta, Canada during the First Two Waves of the COVID-19 Pandemic.

We systematically evaluated SARS-CoV-2 IgG positivity in a provincial cohort to understand the local epidemiology of COVID-19 and support evidence-based public health decisions. Residual blood samples were collected for serology testing over 5-day periods monthly from June 2020 to January 2021 from six clinical laboratories across the province of Alberta, Canada. A total of 93,993 individual patient samples were tested with a SARS-CoV-2 nucleocapsid antibody assay with positives confirmed using a spike antibody assay. Population-adjusted SARS-CoV-2 IgG seropositivity was 0.92% (95% confidence interval [CI]: 0.91 to 0.93%) shortly after the first COVID-19 wave in June 2020, increasing to 4.63% (95% CI: 4.61 to 4.65%) amid the second wave in January 2021. There was no significant difference in seropositivity between males and females (1.39% versus 1.27%; P = 0.11). Ages with highest seropositivity were 0 to 9 years (2.71%, 95% CI: 1.64 to 3.78%) followed by 20 to 29 years (1.58%, 95% CI: 1.12 to 2.04%), with the lowest rates seen in those aged 70 to 79 (0.79%, 95% CI: 0.65 to 0.93%) and >80 (0.78%, 95% CI: 0.60 to 0.97%). Compared to the seronegative group, seropositive patients inhabited geographic areas with lower household income ($87,500 versus $97,500; P < 0.001), larger household sizes, and higher proportions of people with education levels of secondary school or lower, as well as immigrants and visible minority groups (all P < 0.05). A total of 53.7% of seropositive individuals were potentially undetected cases with no prior positive COVID-19 nucleic acid test (NAAT). Antibodies were detectable in some patients up to 9 months post positive NAAT result. This seroprevalence study will continue to inform public health decisions by identifying at-risk demographics and geographical areas. IMPORTANCE Using SARS-CoV-2 serology testing, we assessed the proportion of people in Alberta, Canada (population 4.4 million) positive for COVID-19 antibodies, indicating previous infection, during the first two waves of the COVID-19 pandemic (prior to vaccination programs). Linking these results with sociodemographic population data provides valuable information as to which groups of the population are more likely to have been infected with the SARS-CoV-2 virus to help facilitate public health decision-making and interventions. We also compared seropositivity data with previous COVID-19 molecular testing results. Absence of antibody and molecular testing were highly correlated (95% negative concordance). Positive antibody correlation with a previous positive molecular test was low, suggesting the possibility of mild/asymptomatic infection or other reasons leading individuals from seeking medical attention. Our data highlight that the true estimate of population prevalence of COVID-19 is likely best informed by combining data from both serology and molecular testing.

Retrospective testing of respiratory specimens for COVID-19 to assess for earlier SARS-CoV-2 infections in Alberta, Canada.

Background: The first case of coronavirus disease 2019 (COVID-19) in Alberta, Canada, was confirmed on March 5, 2020. Because the virus testing criteria had changed significantly over this time period, we wanted to ascertain whether previous cases of COVID-19 had been missed in the province. Methods: Our aim was to retrospectively evaluate specimens submitted for respiratory virus testing from December 1, 2019, through March 7, 2020, for undetected severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections before the first confirmed case. Results: Testing of 23,517 samples (representing 23,394 patients) identified 1 patient positive for SARS-CoV-2. This specimen was collected on February 24, 2020, from a patient with symptoms consistent with COVID-19 who had recently returned from the western United States. Phylogenetic analysis confirmed this viral isolate belonged to lineage B.1. The epidemiology of this case is consistent with those of other early cases before sustained community transmission, which included a travel history outside of Canada. Conclusion: This exercise provides support that local public health pandemic planning was satisfactory and timely.

Historique: Le premier cas de maladie à coronavirus 2019 (COVID-19) en Alberta, au Canada, a été confirmé le 15 mars 2020. Puisque les critères de dépistage ont beaucoup évolué pendant cette période, les chercheurs voulaient vérifier si des cas antérieurs de COVID-19 avaient été omis dans la province. Méthodologie: Les chercheurs ont procédé à l'évaluation rétrospective d'échantillons soumis en vue du dépistage d'un virus respiratoire entre le 1er décembre 2019 et le 7 mars 2020, afin de retracer les infections par le coronavirus 2 du syndrome respiratoire aigu sévère (SARS-CoV-2) non décelées avant le premier cas confirmé. Résultats: Le dépistage de 23 517 échantillons (représentant 23 394 patients) a fait ressortir un patient positif au SARS-CoV-2. Le prélèvement avait été effectué le 24 février 2020 chez un patient éprouvant des symptômes correspondant à la COVID-19 revenu récemment de l'ouest des États-Unis. L'analyse phylogénétique a confirmé que l'isolat viral appartenait à la lignée B.1. L'épidémiologie de ce cas est compatible avec celle des autres premiers cas précédant une transmission communautaire soutenue, qui incluait un voyage à l'extérieur du Canada. Conclusion: Cet exercice appuie la pertinence et la rapidité de la planification sanitaire locale de la pandémie.