Universal Polymerase Chain Reaction and Antibody Testing Demonstrate Little to No Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 in a Rural Community

Abstract

Background Limited systematic surveillance for SARS-CoV-2 in the early months of the United States epidemic curtailed accurate appraisal of transmission intensity. Our objective was to perform case detection of an entire rural community to quantify SARS-CoV-2 transmission using PCR and antibody testing. Methods We conducted a cross-sectional survey of SARS-CoV-2 infection in the rural town of Bolinas, California (population 1,620), four weeks following shelter-in-place orders. Participants were tested between April 20 th – 24 th, 2020. Prevalence by PCR and seroprevalence from two forms of antibody testing were performed in parallel (Abbott ARCHITECT IgG and in-house IgG ELISA). Results Of 1,891 participants, 1,312 were confirmed Bolinas residents (>80% community ascertainment). Zero participants were PCR positive. Assuming 80% sensitivity, it would have been unlikely to observe these results (p<0.05) if there were >3 active infections in the community. Based on antibody results, estimated prevalence of prior infection was 0.16% (95% CrI: 0.02%, 0.46%). The positive predictive value (PPV) of a positive result on both tests was 99.11% (95% CrI: 95.75%, 99.94%), compared to PPV 44.19%-63.32% (95% CrI range 3.25%-98.64%) if one test was utilized. Conclusions Four weeks following shelter-in-place, SARS-CoV-2 infection in a rural Northern California community was extremely rare. In this low prevalence setting, use of two antibody tests increased seroprevalence estimate precision. This was one of the first community-wide studies to successfully implement synchronous PCR and antibody testing, particularly in a rural setting. Widespread testing remains an underpinning of effective disease control in conjunction with consistent uptake of public health measures.

Citywide serosurveillance of the initial SARS-CoV-2 outbreak in San Francisco using electronic health records

“…However, like many other areas, a high proportion of asymptomatic infections and limited access to diagnostic testing during this time makes it difficult to interpret these numbers. Results from an early San Francisco seroprevalence study conducted on convenience samples in late March to early April 2020 suggested that <1% of the population had been infected overall 16 , in contrast to a seroprevalence of >6% estimated by a community study focusing on a specific neighborhood, particularly among the Hispanic/Latinx population 17 but consistent with a survey of a rural Bay Area community 18 . The lack of citywide, representative seroprevalence estimates during this time period limits the ability to determine to what degree these discrepancies reflect heterogenous exposure or differences in study design.…”

SARS-CoV-2 Cumulative Incidence and Period Seroprevalence: Results From a Statewide Population-Based Serosurvey in California

“…With nearly 40 million residents representing a geographically and demographically diverse population, conducting representative serosurveys generalizable to California’s population has been an ongoing challenge. Seroprevalence estimates from several local and population-specific serosurveys in California have ranged from <1% to >21% and have varied greatly depending on the sampling period, geographic location, and population sampled [ 4–7 , 22–24 , 30–33 ]. CDC estimates for California using clinical laboratory residual specimens ranged from 4.1% in September 2020 to 18.1% in January 2021, with an estimated seroprevalence from mid-November 2020 of 6.6% [ 34 ].…”

“…When conducted in population-based samples, serosurveys can provide relatively unbiased estimates of the burden of disease in a geographic area and of disparities in infection across population groups. To date, most California-based serosurveys have had limited geographic reach or were conducted in specific populations, such as blood donors or essential workers, who are likely not representative of the general population of the state [ 4–7 ]. Given California’s diverse population of ~40 million, a representative statewide study was needed to capture data from people less likely to be included in convenience samples and to understand the full extent of SARS-CoV-2 burden in California and disparities that might exist by population characteristics and behaviors.…”

Design of a population-based longitudinal cohort study of SARS-CoV-2 incidence and prevalence among adults in the San Francisco Bay Area

“…Numerous cross-sectional studies aimed at determining population-levels of infection have been conducted in the U.S., including in Chicago, New York, Indiana, Georgia, California [2] , [3] , [4] , [5] , [6] , [7] , [8] , [9] , as well as country-wide and internationally [10] , [11] , [12] , [13] , [14] , [15] , [16] , [17] , [18] . Approaches to determining the prevalence of infection have also involved testing of remnant blood samples [19] , [20] , [21] including from dialysis patients [ 22 , 23 ].…”