Investigation of SARS-CoV-2 outbreaks in six care homes in London, April 2020

Shamez Ladhani*, J. Yimmy Chow, Roshni Janarthanan, Jonathan Fok, Emma Crawley-Boevey, Amoolya Vusirikala, Elena Fernandez, Marina Sanchez Perez, Suzanne Tang, Kate Dun-Campbell, Edward Wynne Evans, Anita Bell, Bharatkumar Patel, Zahin Amin-Chowdhury, Felicity Aiano, Karthikeyan Paranthaman, Thomas Ma, Maria Saavedra-Campos, Richard Myers, Joanna EllisAngie Lackenby, Robin Gopal, Monika Patel, Colin Brown, Meera Chand-Kumar, Kevin Brown, Mary Ramsay, Susan Hopkins, Nandini Shetty, Maria Zambon

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


Background: Care homes are experiencing large outbreaks of COVID-19 associated with high case-fatality rates. We conducted detailed investigations in six London care homes reporting suspected COVID-19 outbreaks during April 2020. Methods: Residents and staff had nasal swabs for SARS CoV-2 testing using RT-PCR and were followed-up for 14 days. They were categorized as symptomatic, post-symptomatic or pre-symptomatic if they had symptoms at the time of testing, in the two weeks before or two weeks after testing, respectively, or asymptomatic throughout. Virus isolation and whole genome sequencing (WGS) was also performed. Findings: Across the six care homes, 105/264 (39.8%) residents were SARS CoV-2 positive, including 28 (26.7%) symptomatic, 10 (9.5%) post-symptomatic, 21 (20.0%) pre-symptomatic and 46 (43.8%) who remained asymptomatic. Case-fatality at 14-day follow-up was highest among symptomatic SARS-CoV-2 positive residents (10/28, 35.7%) compared to asymptomatic (2/46, 4.3%), post-symptomatic (2/10, 20.0%) or pre-symptomatic (3/21,14.3%) residents. Among staff, 53/254 (20.9%) were SARS-CoV-2 positive and 26/53 (49.1%) remained asymptomatic. RT-PCR cycle-thresholds and live-virus recovery were similar between symptomatic/asymptomatic residents/staff. Higher RT-PCR cycle threshold values (lower virus load) samples were associated with exponentially decreasing ability to recover infectious virus (P<0.001). WGS identified multiple (up to 9) separate introductions of different SARS-CoV-2 strains into individual care homes. Interpretation: A high prevalence of SARS-CoV-2 positivity was found in care homes residents and staff, half of whom were asymptomatic and potential reservoirs for on-going transmission. A third of symptomatic SARS-CoV-2 residents died within 14 days. Symptom-based screening alone is not sufficient for outbreak control. Funding: None

Original languageEnglish
Article number100533
Publication statusPublished - Sep 2020

Bibliographical note

Funding Information:
The authors are very grateful to the care home managers, their staff and the residents for their willingness to support the investigation, along with the staff in the immunization and countermeasures division, PHE Operations, the virus reference department, the London Coronavirus Response Cell and Field Services for their help and support with the investigation. The authors would also like to thank Dr Anna Jeffery Smith for her help with microbiological studies and analyses, as well as Natalie Groves and Ulf Schaefer for their help with the genomic analysis. The investigation was conducted as Public Health England's duty to manage outbreaks in response the COVID-19 outbreak. There are no additional data for the Care Home Investigation in addition to what we have already reported. Public Health England, Study conception (SNL, JYC, EW-E), study oversight (JYC), oversight of laboratory work (MZ), protocol development (EF, RJ, MS-P,KP, JF, E-CB, KD-C, AV, AB, ST, ZAC, FA, BP, EW-E, JYC, CB, MC, MZ), data collection (EF, RJ, MS-P,KP, JF, E-CB, KD-C, AV, AB, ST, ZAC, FA, BP, TM, EW-E, JYC), operational conduct (EF, RJ, MS-P,KP, JF, E-CB, KD-C, AV, AB, ST, ZAC, FA, BP, TM, NS, EW-E), manuscript preparation (EF, RJ, MS-P,KP, JF, E-CB, KD-C, AV, AB, ST, ZAC, FA, BP, KEB, MP, RG, NS, JE, EW-E, MS-C, MER, SH, CB, RM, MC, AL, MZ), virus isolation (MP,RG), PCR detection work (JE), laboratory genomics (AL), bioinformatics analyses (RM, MC), data analysis (KEB, MP, RG, NS, JE, MER, SH, RM, MZ).

Publisher Copyright:
© 2020


  • Care homes
  • Case-fatality rate
  • Covid-19
  • Symptoms


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