CDC researchers report virus rate in asymptomatic SNF residents

A new study from the Centers for Disease Control and Prevention (CDC) COVID-19 Investigation Team confirms that symptom-based screening of skilled nursing facility (SNF) residents might fail to identify all COVID-19 cases—something that has been widely reported anecdotally.

Following identification of a case of coronavirus disease 2019 (COVID-19) in a health care worker at a SNF in Washington State, 76 of 82 residents of the facility were tested for SARS-CoV-2; 23 (30.3%) had positive test results, approximately half of whom were asymptomatic or presymptomatic on the day of testing.

One week after testing, the 13 residents who had positive test results and were asymptomatic on the date of testing were reassessed; 10 had developed symptoms and were recategorized as presymptomatic at the time of testing (Table 2). The most common signs and symptoms that developed were fever (eight residents), malaise (six), and cough (five). The mean interval from testing to symptom onset in the presymptomatic residents was 3 days. Three residents with positive test results remained asymptomatic.

This analysis suggests that symptom screening could initially fail to identify approximately one half of SNF residents with SARS-CoV-2 infection. Unrecognized asymptomatic and presymptomatic infections might contribute to transmission in these settings, the authors wrote. It is not known whether the findings apply to the general population, including younger people, those without underlying medical conditions, or similarly aged populations in the general community, the authors added.

The findings were e-published on March 27 by Morbidity and Mortality Weekly Report: