Mass testing after a single suspected or confirmed case of COVID-19 in London care homes, April–May 2020: implications for policy and practice

Tang, Suzanne; Perez, Marina Sanchez; Saavedra-Campos, Maria; Paranthaman, Karthik; Myers, Richard; Fok, Jonathan; Crawley-Boevey, Emma; Dun-Campbell, Kate; Janarthanan, Roshni; Fernandez, Elena; Vusirikala, Amoolya; Patel, Bharat; Ma, Thomas; Amin-Chowdhury, Zahin; Shetty, Nandini; Zambon, Maria; Bell, Anita; Wynne-Evans, Edward; Chow, Yimmy; Ladhani, Shamez

Introduction: Previous investigations have identified high rates of SARS-CoV-2 infection among residents and staff in care homes reporting an outbreak of COVID-19. We investigated care homes reporting a single suspected or confirmed case to assess whether early mass testing might reduce risk of transmission during the peak of the pandemic in London. Methods: Between 18–27 April 2020, residents and staff in care homes reporting a single case of COVID-19 to Public Health England had a nasal swab to test for SARS-CoV-2 infection by RT-PCR and subsequent whole genome sequencing. Residents and staff in two care homes were re-tested eight days later. Results: Four care homes were investigated. SARS-CoV-2 positivity was 20% (65/333) overall, ranging between 3–59%. Among residents, positivity ranged between 3–76% compared to 3–40% in staff. Half of the SARS-CoV-2 positive residents (23/46, 50%) and 63% of staff (12/19) reported symptoms within 14 days before or after testing. Repeat testing 8 days later in two care homes with the highest infection rates identified only two new cases. Genomic analysis demonstrated a small number of introductions of the virus into care homes, and distinct clusters within three of the care homes. Conclusions: We found extensive but variable rates of SARS-CoV-2 infection among residents and staff in care homes reporting a single case of COVID-19. While routine whole home testing has now been adopted into practice, care homes must remain vigilant and should be encouraged to report a single suspected case, which should trigger appropriate outbreak control measures.