Timely Intervention and Control of a Novel Coronavirus (COVID-19) Outbreak at a Large Skilled Nursing Facility - San Francisco, California, 2020.

OBJECTIVE: To describe epidemiologic and genomic characteristics of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak in a large skilled nursing facility (SNF), and the strategies that controlled transmission. DESIGN, SETTING, AND PARTICIPANTS: Cohort study during March 22-May 4, 2020 of all staff and residents at a 780-bed SNF in San Francisco, California. METHODS: Contact tracing and symptom screening guided targeted testing of staff and residents; respiratory specimens were also collected through serial point prevalence surveys (PPS) in units with confirmed cases. Cases were confirmed by real-time reverse transcription-polymerase chain reaction testing for SARS-CoV-2; whole genome sequencing (WGS) characterized viral isolate lineages and relatedness. Infection prevention and control (IPC) interventions included restricting from work any staff who had close contact to a confirmed case; restricting movements between units; implementing surgical face masking facility-wide; and recommended PPE (isolation gown, gloves, N95 respirator and eye protection) for clinical interactions in units with confirmed cases. RESULTS: Of 725 staff and residents tested through targeted testing and serial PPS, twenty-one (3%) were SARS-CoV-2-positive; sixteen (76%) staff and 5 (24%) residents. Fifteen (71%) were linked to a single unit. Targeted testing identified 17 (81%) cases; PPS identified 4 (19%). Most (71%) cases were identified prior to IPC intervention. WGS was performed on SARS-CoV-2 isolates from four staff and four residents; five were of Santa Clara County lineage and the three others were distinct lineages. CONCLUSIONS: Early implementation of targeted testing, serial PPS, and multimodal IPC interventions limited SARS-CoV-2 transmission within the SNF.