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SARS-CoV-2 infection in London, England: changes to community point prevalence around lockdown time, March–May 2020
  1. Michael Edelstein,
  2. Chinelo Obi,
  3. Meera Chand,
  4. Susan Hopkins,
  5. Kevin Brown,
  6. Mary Ramsay
  1. National Infection Service, Public Health England, London, UK
  1. Correspondence to Michael Edelstein, National Infection Service, Public Health England, 61 Colindale Avenue, London NW9 5EQ UK; Michael.edelstein{at}phe.gov.uk

Abstract

Background The UK has been one of the European countries most affected by COVID-19 pandemic. The UK implemented a lockdown in March 2020, when testing policy at the time was focusing on hospitalised cases. Limited information is therefore available on the impact of the lockdown on point prevalence in the community. We assessed COVID-19 point prevalence in London between early April and early May 2020, which approximately reflect infection around the time of the lockdown and 3–5 weeks into lockdown.

Methods We tested 1064 participants of a community surveillance cohort for acute COVID-19 infection using PCR in London in April and May 2020 and described positivity as well as characteristics and symptoms of the participants.

Results Point prevalence decreased from 2.2% (95% CI 1.4 to 3.5) in early April to 0.2% (95% CI 0.03 to 1.6) in early May. 22% of those who tested positive in April were asymptomatic. Extrapolation from reports of confirmed cases suggest that 5–7.6% of total infections were confirmed by testing during this period.

Conclusion COVID-19 point prevalence in the community sharply decreased after lockdown was implemented. This study is based on a small sample and regular seroprevalence studies are needed to better characterise population-level immunity.

  • Epidemics
  • communicable diseases
  • control of diseases
https://creativecommons.org/licenses/by/4.0/

This is an open access article distributed in accordance with the Creative Commons Attribution 4.0 Unported (CC BY 4.0) license, which permits others to copy, redistribute, remix, transform and build upon this work for any purpose, provided the original work is properly cited, a link to the licence is given, and indication of whether changes were made. See: https://creativecommons.org/licenses/by/4.0/.

https://doi.org/10.1136/jech-2020-214730

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    Footnotes

    • Twitter Michael Edelstein @epi_michael.

    • Contributors MR, KB and ME designed the study. ME, CO, MR and KB collected and analysed the data. ME, MR, MC and SH interpreted the findings in the context of broader England COVID-19 surveillance outputs. All authors contributed to drafting the manuscript.

    • Funding This study was conducted as part of routine surveillance activities and no specific funding was obtained.

    • Competing interests This study was conducted by Public Health England as part of routine surveillance activities.

    • Patient consent for publication Not required.

    • Ethics approval Ethics approval for inviting participants for self-swabbing was obtained when Flusurvey was initially set up in 2008/2009, and each participant was individually reconsented.

    • Provenance and peer review Not commissioned; externally peer reviewed.