• Eliza R Thompson, Faith S Williams, Pat A Giacin, Shay Drummond, Eric Brown, Meredith Nalick, Qian Wang, Jay R McDonald, and Abigail L Carlson.
• Washington University School of Medicine, St Louis, Missouri.
• Infect Control Hosp Epidemiol. 2021 Mar 29: 1-7.

ObjectivesTo assess extent of a healthcare-associated outbreak of severe acute respiratory coronavirus virus 2 (SARS-CoV-2) and to evaluate the effectiveness of infection control measures, including universal masking.DesignOutbreak investigation including 4 large-scale point-prevalence surveys.SettingIntegrated VA healthcare system with 2 facilities and 330 beds.ParticipantsIndex patient and 250 exposed patients and staff.MethodsWe identified exposed patients and staff and classified them as probable and confirmed cases based on symptoms and testing. We performed a field investigation and an assessment of patient and staff interactions to develop probable transmission routes. Infection prevention interventions included droplet and contact precautions, employee quarantine, and universal masking with medical and cloth face masks. We conducted 4 point-prevalence surveys of patient and staff subsets using real-time reverse-transcriptase polymerase chain reaction for SARS-CoV-2.ResultsAmong 250 potentially exposed patients and staff, 14 confirmed cases of coronavirus disease 2019 (COVID-19) were identified. Patient roommates and staff with prolonged patient contact were most likely to be infected. The last potential date of transmission from staff to patient was day 22, the day universal masking was implemented. Subsequent point-prevalence surveys in 126 patients and 234 staff identified 0 patient cases and 5 staff cases of COVID-19, without evidence of healthcare-associated transmission.ConclusionsUniversal masking with medical face masks was effective in preventing further spread of SARS-CoV-2 in our facility in conjunction with other traditional infection prevention measures.

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