Lessons from Mass-Testing for Coronavirus Disease 2019 in Long-Term Care Facilities for the Elderly in San Francisco

Abstract

Coronavirus disease 2019 can cause significant mortality in the elderly in long-term care facilities (LTCF). We describe 4 LTCF outbreaks where mass testing identified a high proportion of asymptomatic infections (4%-41% in healthcare workers and 20%-75% in residents), indicating that symptom-based screening alone is insufficient for monitoring for COVID-19 transmission.