St. Louis County Announces Results of COVID-19 Prevalence Testing
ST. LOUIS COUNTY, MO (November 23, 2020) – At least one out of every 100 St. Louis County adult residents had an active COVID-19 infection earlier this fall, while about five out of every 100 adults had contracted the disease at some earlier point, according to test results of a representative sample of county residents.
Results of the testing, commissioned by St. Louis County Department of Public Health and launched by the Institute of Public Health at Washington University in St. Louis as he COVID-19 St. Louis County Survey, raised fresh concerns from experts about the high risk of further, rapid spread of the disease in the county – especially given the explosion in COVID-19 cases since the testing was conducted.
The testing measured active COVID-19 infection based on nasal swab tests, and past infections were determined by antibody/blood tests. The findings suggest that over the course of the testing period, from mid-August through mid-October, about 1.2% of St. Louis County adult residents – some 9,500 -- had an active COVID-19 infection at any given point, and 5% of adult residents, or about 39,000, had COVID-19 antibodies, indicating past infection.
Given that the testing occurred before the most recent surge of cases, current prevalence is almost certainly much higher.
“With so many people actively infected with COVID-19 earlier this fall – and contagious – we’re already seeing that the illness can spread quickly to even larger portions of the population,” Elvin Geng, MD, MPH, professor in the Division of Infectious Diseases at Washington University School of Medicine, said. These findings, the first representative assessment of the burden of disease in St. Louis County, provide another indication that the region is still highly vulnerable to the COVID-19 pandemic. Since antibodies likely confer immunity, the survey indicates that about 95% of St. Louis County’s 1 million adults and children were still susceptible to the virus in mid-October.
“The relatively small proportion of the population that had evidence of previous infection via antibody testing means that the size of the current surge we are experiencing in the region could be quite dramatic,” Geng said. “Under these conditions, we are already seeing a steep rise in cases that has the potential to overwhelm area hospitals.”
Public health leaders in the region agree that proven preventive measures such as wearing masks, staying at least six feet apart from others, avoiding crowds and washing hands are essential to slowing the dramatic rise in cases.
"These findings, together with the recent surge in new cases, only reinforce the need for every one of us to show that we care for our loved ones, friends and community by taking steps to stop the spread,” Spring Schmidt, acting director of the St. Louis County Department of Public Health, said.
Working with the county, the Institute for Public Health teamed with other local public health and health-care providers to conduct a phone survey of a representative sample of St. Louis County residents. Participants were offered free COVID-19 testing at convenient locations across the county, regardless of whether they had symptoms. They could choose to receive diagnostic testing to detect active COVID-19 infection or antibody testing to detect previous infection. Transportation to and from testing sites was provided free of charge to those who needed it.
Over the course of the survey, more than 1,300 St. Louis County residents received a diagnostic test (PCR nasal swab) and/or an antibody test (blood test). More than 3,300 residents completed questionnaires to gauge how the pandemic had affected their lives. While detailed results of the questionnaire are forthcoming, initial analyses show that a quarter of those surveyed had experienced wage reduction or job loss due to COVID-19, highlighting the pandemic’s wide-ranging impact.
In addition to the estimates of overall prevalence, the survey found that Black residents were more than twice as likely to have had COVID-19 than white residents (8.3% vs 3.4%), based on results of nasal swab tests and antibody/blood tests. This disparity also is apparent in higher COVID-19 death rates among Black residents than white residents. St. Louis County has directed CARES Act Healthcare Response funding specifically to the hardest-hit communities, mostly in north St. Louis County, and will continue to strive toward health equity in ongoing pandemic response efforts.
“This survey gives us critical information for understanding the impact of COVID-19 in the community and making decisions on how to shape our response to best help our residents,” said County Executive Sam Page. “We are grateful to have these informative survey results to help guide our evidence-based approach to fighting the pandemic and ensuring our public health policies address these inequities.”
The St. Louis County Department of Public Health allocated $1.99 million of its share of federal CARES Act funding to pay for the survey, as part of its efforts to respond to the pandemic. The department ultimately will use the project data and results to help inform decisions about public health and healthcare delivery during the pandemic and possible future public health emergencies.
The Institute for Public Health at Washington University in St. Louis managed the project and coordinated data flow and analysis. Collaborators for the COVID-19 testing included BJC HealthCare, SSM Health, Mercy and the St. Louis County Department of Public Health. The University of Missouri helped design and conduct the survey. The St. Louis Integrated Health Network provided consultation to the team related to community engagement and assisted in the delivery of follow-up services.
Director of Communications
St. Louis County Department of Public Health
Assistant Director, Medical Public Affairs
Office of Medical Public Affairs
Washington University School of Medicine