Asymptomatic SARS-CoV-2 Infection and COVID-19 Mortality During an Outbreak Investigation in a Skilled Nursing Facility

Abstract

Background: Outbreaks of coronavirus disease 2019 (COVID-19) have been reported in nursing homes and assisted living facilities; however, the extent of asymptomatic and presymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in this high-risk population remains unclear.

Methods: We conducted an investigation of the first known outbreak of SARS-CoV-2 at a skilled nursing facility (SNF) in Illinois on 15 March 2020 and followed residents for 30 days. We tested 126/127 residents for SARS-CoV-2 via reverse-transcription polymerase chain reaction and performed symptom assessments. We calculated the point prevalence of SARS-CoV-2 and assessed symptom onset over 30-day follow-up to determine: (1) the proportion of cases who were symptomatic, presymptomatic, and asymptomatic and (2) incidence of symptoms among those who tested negative. We used the Kaplan-Meier method to determine the 30-day probability of death for cases.

Results: Of 126 residents tested, 33 had confirmed SARS-CoV-2 on 15 March. Nineteen (58%) had symptoms at the time of testing, 1 (3%) developed symptoms over follow-up, and 13 (39%) remained asymptomatic. Thirty-five residents who tested negative on 15 March developed symptoms over follow-up; of these, 3 were re-tested and 2 were positive. The 30-day probability of death among cases was 29%.

Conclusions: SNFs are particularly vulnerable to SARS-CoV-2, and residents are at risk of severe outcomes. Attention must be paid to preventing outbreaks in these and other congregate care settings. Widespread testing and infection control are key to help prevent COVID-19 morbidity and mortality in these high-risk populations.

Keywords: COVID-19; SARS-CoV-2; outbreak investigation; skilled nursing facility.

Figure 1.

SARS-CoV-2 test results and symptom onset among Facility A residents. Abbreviations: IDPH, Illinois Department of Public Health; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

Figure 2.

Timeline of testing, symptom onset, hospital admission, and death for (a) confirmed cases and (b) persons under investigation. Abbreviation: SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

Figure 3.

Kaplan-Meier survival curve of 35 residents with confirmed SARS-CoV-2 infection. Cases were followed from the date they tested positive to death or administrative censoring at 30 days or 14 April, whichever occurred first. Abbreviations: CI, confidence interval; SARS-CoV2, severe acute respiratory syndrome coronavirus 2.