SARS-CoV-2 Seroprevalence Survey Among District Residents Presenting for Serologic Testing at Three Community-Based Test Sites — Washington, DC, July–August, 2020
medRxiv(2021)
Abstract
Background The District of Columbia (DC), a major metropolitan area, continues to see community transmission of SARS-CoV-2. While serologic testing does not indicate current SARS-CoV-2 infection, it can indicate prior infection and help inform local policy and health guidance. The DC Department of Health (DC Health) conducted a community-based survey to estimate DC’s SARS-CoV-2 seroprevalence and identify seropositivity-associated factors.
Methods A mixed-methods cross-sectional serology survey was conducted among a convenience sample of DC residents during July 27 – August 21, 2020. Free serology testing was offered at three public test sites. Participants completed an electronic questionnaire on household and demographic characteristics, COVID-like illness (CLI) since January 1, 2020, comorbidities, and SARS-CoV-2 exposures. Univariate and bivariate analyses were conducted to describe the sample population and assess factors associated with seropositivity.
Results Among a sample of 671 participants, 51 individuals were seropositive, yielding an estimated seroprevalence of 7.6%. More than half (56.9%) of the seropositive participants reported no prior CLI; nearly half (47.1%) had no prior SARS-CoV-2 testing. Race/ethnicity, prior SARS-CoV-2 testing, prior CLI, employment status, and contact with confirmed COVID-19 cases were associated with seropositivity (P<0.05). Among those reporting prior CLI, loss of taste or smell, duration of CLI, fewer days between CLI and serology test, or prior viral test were associated with seropositivity (P≤0.006).
Conclusions These findings indicate many seropositive individuals reported no symptoms consistent with CLI since January or any prior SARS-CoV-2 testing. This underscores the potential for cases to go undetected in the community and suggests wider-spread transmission than previously reported in DC.
What is already known on this subject? Traditional case-based detection and syndromic surveillance efforts might not identify mildly symptomatic or asymptomatic SARS-CoV-2 infections. This is particularly true among people in the general population who do not have increased risk of severe illness or might not be tested otherwise. Consequently, the true population prevalence of prior SARS-CoV-2 infections might not be known.
What this study adds? A community-based seroprevalence survey conducted in Washington, DC, during July 27 – August 21, 2020 estimated that 7.6% of the convenience sample had antibodies to SARS-CoV-2, indicating prior infection. At the time of this survey, most of the participants reported that they had not been previously infected with or tested for SARS-CoV-2. These findings highlight both the value of serologic surveillance in complementing other surveillance methods, and the importance of continued prevention and mitigation measures, such as maintaining physical distances of at least 6 feet, avoiding crowds and poorly ventilated spaces, practicing frequent hand hygiene, and wearing face masks properly and consistently around people who do not live with you.
### Competing Interest Statement
The authors have declared no competing interest.
### Clinical Trial
This was not a clinical trial and did not require a clinical trial ID. This was a cross-sectional survey design.
### Funding Statement
This report was supported in part by an appointment to the Applied Epidemiology Fellowship Program administered by the Council of State and Territorial Epidemiologists (CSTE) and funded by the Centers for Disease Control and Prevention (CDC) Cooperative Agreement Number 1NU38OT000297-01-00.
### Author Declarations
I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.
Yes
The details of the IRB/oversight body that provided approval or exemption for the research described are given below:
This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy. Third party review was conducted by Human Subjects Lead; eocevent412@cdc.gov; CDC Incident Management System. This activity was reviewed by DC Health IRBPH and CDC, and was conducted consistent with applicable federal law and CDC policy.
All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived.
Yes
I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).
Yes
I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.
Yes
Analyses can be provided upon request. Provision of raw data will not be shared externally outside of DC Health.
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Key words
serologic testing,sars-cov,community-based
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