{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T08:18:38Z","timestamp":1787818718062,"version":"build-2784847793"},"reference-count":25,"publisher":"Oxford University Press (OUP)","issue":"3","license":[{"start":{"date-parts":[[2021,5,11]],"date-time":"2021-05-11T00:00:00Z","timestamp":1620691200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"UK Government\u2019s Department of Health and Social Care"},{"DOI":"10.13039\/100018336","name":"National Institute for Health Research Health Protection Research Unit","doi-asserted-by":"publisher","award":["NIHR200915"],"award-info":[{"award-number":["NIHR200915"]}],"id":[{"id":"10.13039\/100018336","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100013373","name":"NIHR Biomedical Research Centre, Oxford","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100013373","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2022,2,11]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>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.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>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.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>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\u201312.0%) at Ct = 15 and 4.5% (95% CI 4.4\u20134.6%) at Ct = 30. B.1.1.7 infection increased PCR-positive results by ~50%, (eg, 1.55-fold, 95% CI 1.49\u20131.61, at Ct = 20). PCR-positive results were most common in household contacts (at Ct = 20.1, 8.7% [95% CI 8.6\u20138.9%]), followed by household visitors (7.1% [95% CI 6.8\u20137.3%]), contacts at events\/activities (5.2% [95% CI 4.9\u20135.4%]), work\/education (4.6% [95% CI 4.4\u20134.8%]), and least common after outdoor contact (2.9% [95% CI 2.3\u20133.8%]). 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\u201389.6%) and 83.0% (95% CI 82.8\u201383.1%) of cases with PCR-positive contacts, respectively.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>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.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1093\/cid\/ciab421","type":"journal-article","created":{"date-parts":[[2021,5,5]],"date-time":"2021-05-05T17:40:37Z","timestamp":1620236437000},"page":"407-415","source":"Crossref","is-referenced-by-count":94,"title":["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"],"prefix":"10.1093","volume":"74","author":[{"given":"Lennard Y W","family":"Lee","sequence":"first","affiliation":[{"name":"Nuffield Department of Medicine, University of Oxford, United Kingdom"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Stefan","family":"Rozmanowski","sequence":"additional","affiliation":[{"name":"Department of Health and Social Care, UK Government, London, United 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Kingdom"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Derrick W","family":"Crook","sequence":"additional","affiliation":[{"name":"Nuffield Department of Medicine, University of Oxford, United Kingdom"},{"name":"NIHR Oxford Biomedical Research Centre, University of Oxford, Oxford,United Kingdom"},{"name":"NIHR Health Protection Research Unit in in Healthcare Associated Infections and Antimicrobial Resistance, University of Oxford, Oxford, United Kingdom"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nick","family":"Gent","sequence":"additional","affiliation":[{"name":"Public Health England, London,United Kingdom"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"A Sarah","family":"Walker","sequence":"additional","affiliation":[{"name":"Nuffield Department of Medicine, University of Oxford, United Kingdom"},{"name":"NIHR Oxford Biomedical Research Centre, University of Oxford, Oxford,United Kingdom"},{"name":"NIHR Health Protection 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