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Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infectivity by Viral Load, S Gene Variants and Demographic Factors, and the Utility of Lateral Flow Devices to Prevent Transmission.
Lee, Lennard Y W; Rozmanowski, Stefan; Pang, Matthew; Charlett, Andre; Anderson, Charlotte; Hughes, Gareth J; Barnard, Matthew; Peto, Leon; Vipond, Richard; Sienkiewicz, Alex; Hopkins, Susan; Bell, John; Crook, Derrick W; Gent, Nick; Walker, A Sarah; Peto, Tim E A; Eyre, David W.
  • Lee LYW; Nuffield Department of Medicine, University of Oxford, United Kingdom.
  • Rozmanowski S; Department of Health and Social Care, UK Government, London, United Kingdom.
  • Pang M; Department of Health and Social Care, UK Government, London, United Kingdom.
  • Charlett A; Public Health England, London,United Kingdom.
  • Anderson C; Public Health England, London,United Kingdom.
  • Hughes GJ; Public Health England, London,United Kingdom.
  • Barnard M; Department of Health and Social Care, UK Government, London, United Kingdom.
  • Peto L; Nuffield Department of Medicine, University of Oxford, United Kingdom.
  • Vipond R; Public Health England, Porton Down,United Kingdom.
  • Sienkiewicz A; Public Health England, Porton Down,United Kingdom.
  • Hopkins S; Public Health England, London,United Kingdom.
  • Bell J; Nuffield Department of Medicine, University of Oxford, United Kingdom.
  • Crook DW; Nuffield Department of Medicine, University of Oxford, United Kingdom.
  • Gent N; NIHR Oxford Biomedical Research Centre, University of Oxford, Oxford,United Kingdom.
  • Walker AS; NIHR Health Protection Research Unit in in Healthcare Associated Infections and Antimicrobial Resistance, University of Oxford, Oxford, United Kingdom.
  • Peto TEA; Public Health England, London,United Kingdom.
  • Eyre DW; Nuffield Department of Medicine, University of Oxford, United Kingdom.
Clin Infect Dis ; 74(3): 407-415, 2022 02 11.
Article in English | MEDLINE | ID: covidwho-1684538
ABSTRACT

BACKGROUND:

How severe acute respiratory syndrome coronavirus 2 (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 1 September 2020 and 28 February 2021. We used multivariable logistic regression to investigate relationships between polymerase chain reaction (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 1 of 4 LFDs.

RESULTS:

In total, 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 cycle threshold [Ct] values), for example, 11.7% (95% confidence interval [CI] 11.5-12.0%) at Ct = 15 and 4.5% (95% CI 4.4-4.6%) at Ct = 30. B.1.1.7 infection increased PCR-positive results by ~50%, (eg, 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% [95% CI 6.8-7.3%]), contacts at events/activities (5.2% [95% CI 4.9-5.4%]), work/education (4.6% [95% CI 4.4-4.8%]), and least common after outdoor contact (2.9% [95% CI 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% (95% CI 89.4-89.6%) and 83.0% (95% CI 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.
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Full text: Available Collection: International databases Database: MEDLINE Main subject: SARS-CoV-2 / COVID-19 Type of study: Diagnostic study / Observational study / Prognostic study Topics: Variants Limits: Child / Humans Language: English Journal: Clin Infect Dis Journal subject: Communicable Diseases Year: 2022 Document Type: Article Affiliation country: Cid

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Full text: Available Collection: International databases Database: MEDLINE Main subject: SARS-CoV-2 / COVID-19 Type of study: Diagnostic study / Observational study / Prognostic study Topics: Variants Limits: Child / Humans Language: English Journal: Clin Infect Dis Journal subject: Communicable Diseases Year: 2022 Document Type: Article Affiliation country: Cid