Prevalence of SARS-CoV-2 infection in previously undiagnosed health care workers at the onset of the U.S. COVID-19 epidemic
Authors: Barrett Emily S. , Horton Daniel B. , Roy Jason , Gennaro Maria Laura , Brooks Andrew , Tischfield Jay , Greenberg Patricia , Andrews Tracy , Jagpal Sugeet , Reilly Nancy , Blaser Martin J. , Carson Jeffrey L. , Panettieri Reynold A. 
Published: April 2020

Importance

Healthcare workers are presumed to be at increased risk of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection due to occupational exposure to infected patients. However, no epidemiological study has examined the prevalence of SARS-CoV-2 infection in a cohort of healthcare workers during the early phase of community transmission.

Objective

To determine the baseline prevalence of SARS-CoV-2 infection in a cohort of previously undiagnosed healthcare workers and a comparison group of non-healthcare workers.

Design

Prospective cohort study

Setting

A large U.S. university and two affiliated university hospitals

Participants

546 health care workers and 283 non-health care workers with no known prior SARS-CoV-2 infection

Exposure

Healthcare worker status and role

Main outcome(s) and measure(s)

SARS-CoV-2 infection status as determined by presence of SARS-CoV-2 RNA in oropharyngeal swabs.

Results

At baseline, 41 (5.0%) of participants tested positive for SARS-CoV-2 infection, of whom 14 (34.2%) reported symptoms. The prevalence of SARS-CoV-2 infection was higher among healthcare workers (7.3%) than in non-healthcare workers (0.4%), representing a 7.0% greater absolute risk (95% confidence interval for risk difference 4.7%, 9.3%). The majority of infected healthcare workers (62.5%) worked as nurses. Positive tests increased across the two weeks of cohort recruitment in line with rising confirmed cases in the hospitals and surrounding counties.

Conclusions and relevance

In a prospective cohort conducted in the early phases of community transmission, healthcare workers had a higher prevalence of SARS-CoV-2 infection than non-healthcare workers, attesting to the occupational hazards of caring for patients in this crisis. Baseline data reported here will enable us to monitor the spread of infection and examine risk factors for transmission among healthcare workers. These results will inform optimal strategies for protecting the healthcare workforce, their families, and their patients.

Clinicaltrials.gov registration number:NCT04336215

Key points

Question

Among previously undiagnosed individuals, is the prevalence of SARS-CoV-2 infection higher in U.S. healthcare workers compared to non-healthcare workers in the early phase of the U.S. COVID-19 epidemic?

Findings

The prevalence of SARS-CoV-2 infection was 7.3% in healthcare workers and 0.4% in non-healthcare workers, representing 7.0% greater absolute risk in the former (95% confidence interval for risk difference 4.7%, 9.3%). Infections were most common among nursing staff.

Meaning

Health care workers, particularly those with high levels of close patient contact, may be particularly vulnerable to SARS-CoV-2 infection. Additional strategies are needed to protect these critical frontline workers.