Study population and setting
The study population included potentially linked individuals to a single confirmed index case of COVID-19 identified on February 28, 2020, and subsequent cases in a long-term care facility in King Country Washington. The investigation included individuals identified through contact tracing between February 28 – March 18, 2020. Data were collected through Public Health–Seattle and King County (PHSKC) on demographic characteristics, clinical status, and results of laboratory testing through the local surveillance database, which was analyzed alongside laboratory records and case reports obtained from the Washington Disease Reporting System.
Summary of Main Findings
Between February 28 and March 18, 2020, a total of 167 confirmed cases of COVID-19 were found to be epidemiologically linked to single long-term care facility. Confirmed cases included 101 facility residents, 50 health care personnel, and 16 visitors. Overall, the hospitalization rate among those infected was 39.5% (66/167), including 54.5% (55/101) among facility residents, 50.0% (8/16) among visitors, and 6.0% (3/50) among staff. The preliminary case fatality rate was 33.7% (34/101) among facility residents and 6.2% (1/16) among visitors.
Use of epidemiological data and contact tracing from an outbreak investigation of COVID-19 linked to a long-term care facility was a strength. The investigation was led by state (PHSKC) and federal (CDC) public health surveillance and response organizations in response to the emergency.
Residents and staff were not systematically interviewed and tested for SARS-CoV-2, and therefore this investigation may have missed individuals. In particular, individuals were not systematically tested for asymptomatic or pre-symptomatic infections. Additionally, visitors may have been missed from data collection. The epidemic curve in this analysis was presented by date of report but does not represent the timing of disease onset.
This study was novel in that is describes the initial outbreak linked to a long-term care facility of COVID-19 early in the outbreak within the United States.