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Lee LYW, Rozmanowski S, Pang M, et al. SARS-CoV-2 infectivity by viral load, S gene variants and demographic factors and the utility of lateral flow devices to prevent transmission. Clin Infect Dis. 2021;doi: 10.1093/cid/ciab421.
Lee, L. Y. W., Rozmanowski, S., Pang, M., Charlett, A., Anderson, C., Hughes, G. J., Barnard, M., Peto, L., Vipond, R., Sienkiewicz, A., Hopkins, S., Bell, J., Crook, D. W., Gent, N., Walker, A. S., Peto, T. E. A., & Eyre, D. W. (2021). SARS-CoV-2 infectivity by viral load, S gene variants and demographic factors and the utility of lateral flow devices to prevent transmission. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, . https://doi.org/10.1093/cid/ciab421
Lee, Lennard Y W, et al. "SARS-CoV-2 infectivity by viral load, S gene variants and demographic factors and the utility of lateral flow devices to prevent transmission." Clinical infectious diseases : an official publication of the Infectious Diseases Society of America vol. (2021). doi: https://doi.org/10.1093/cid/ciab421
Lee LYW, Rozmanowski S, Pang M, Charlett A, Anderson C, Hughes GJ, Barnard M, Peto L, Vipond R, Sienkiewicz A, Hopkins S, Bell J, Crook DW, Gent N, Walker AS, Peto TEA, Eyre DW. SARS-CoV-2 infectivity by viral load, S gene variants and demographic factors and the utility of lateral flow devices to prevent transmission. Clin Infect Dis. 2021 May 11; doi: 10.1093/cid/ciab421. Epub 2021 May 11. PMID: 33972994; PMCID: PMC8136027.
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Clin Infect Dis. 2021 May 11; doi: 10.1093/cid/ciab421. Epub 2021 May 11.

SARS-CoV-2 infectivity by viral load, S gene variants and demographic factors and the utility of lateral flow devices to prevent transmission.

Clinical infectious diseases : an official publication of the Infectious Diseases Society of America

Lennard Y W Lee, Stefan Rozmanowski, Matthew Pang, Andre Charlett, Charlotte Anderson, Gareth J Hughes, Matthew Barnard, Leon Peto, Richard Vipond, Alex Sienkiewicz, Susan Hopkins, John Bell, Derrick W Crook, Nick Gent, A Sarah Walker, Tim E A Peto, David W Eyre

Affiliations

  1. Nuffield Department of Medicine, University of Oxford, UK.
  2. Department of Health and Social Care, UK Government, London, UK.
  3. Public Health England, London, UK.
  4. Public Health England, Porton Down, UK.
  5. NIHR Oxford Biomedical Research Centre, University of Oxford, Oxford, UK.
  6. NIHR Health Protection Research Unit in in Healthcare Associated Infections and Antimicrobial Resistance, University of Oxford, UK.
  7. Big Data Institute, Nuffield Department of Population Health, University of Oxford, Oxford, UK.

PMID: 33972994 PMCID: PMC8136027 DOI: 10.1093/cid/ciab421

Abstract

BACKGROUND: How SARS-CoV-2 infectivity varies with viral load is incompletely understood. Whether rapid point-of-care antigen lateral flow devices (LFDs) detect most potential transmission sources despite imperfect clinical sensitivity is unknown.

METHODS: We combined SARS-CoV-2 testing and contact tracing data from England between 01-September-2020 and 28-February-2021. We used multivariable logistic regression to investigate relationships between PCR-confirmed infection in contacts of community-diagnosed cases and index case viral load, S gene target failure (proxy for B.1.1.7 infection), demographics, SARS-CoV-2 incidence, social deprivation, and contact event type. We used LFD performance to simulate the proportion of cases with a PCR-positive contact expected to be detected using one of four LFDs.

RESULTS: 231,498/2,474,066(9%) contacts of 1,064,004 index cases tested PCR-positive. PCR-positive results in contacts independently increased with higher case viral loads (lower Ct values) e.g., 11.7%(95%CI 11.5-12.0%) at Ct=15 and 4.5%(4.4-4.6%) at Ct=30. B.1.1.7 infection increased PCR-positive results by ~50%, (e.g. 1.55-fold, 95%CI 1.49-1.61, at Ct=20). PCR-positive results were most common in household contacts (at Ct=20.1, 8.7%[95%CI 8.6-8.9%]), followed by household visitors (7.1%[6.8-7.3%]), contacts at events/activities (5.2%[4.9-5.4%]), work/education (4.6%[4.4-4.8%]), and least common after outdoor contact (2.9%[2.3-3.8%]). Contacts of children were the least likely to test positive, particularly following contact outdoors or at work/education. The most and least sensitive LFDs would detect 89.5%(89.4-89.6%) and 83.0%(82.8-83.1%) of cases with PCR-positive contacts respectively.

CONCLUSIONS: SARS-CoV-2 infectivity varies by case viral load, contact event type, and age. Those with high viral loads are the most infectious. B.1.1.7 increased transmission by ~50%. The best performing LFDs detect most infectious cases.

© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.

Keywords: B.1.1.7 variant; SARS-CoV-2; contact tracing; infectivity; lateral flow device

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