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<jats:sec id="abs1"><jats:title>Background:</jats:title><jats:p>Information on SARS-CoV-2 in representative community surveillance is limited, particularly cycle threshold (Ct) values (a proxy for viral load).</jats:p></jats:sec><jats:sec id="abs2"><jats:title>Methods:</jats:title><jats:p>We included all positive nose and throat swabs 26 April 2020 to 13 March 2021 from the UK’s national COVID-19 Infection Survey, tested by RT-PCR for the N, S, and ORF1ab genes. We investigated predictors of median Ct value using quantile regression.</jats:p></jats:sec><jats:sec id="abs3"><jats:title>Results:</jats:title><jats:p>Of 3,312,159 nose and throat swabs, 27,902 (0.83%) were RT-PCR-positive, 10,317 (37%), 11,012 (40%), and 6550 (23%) for 3, 2, or 1 of the N, S, and ORF1ab genes, respectively, with median Ct = 29.2 (~215 copies/ml; IQR Ct = 21.9–32.8, 14–56,400 copies/ml). Independent predictors of lower Cts (i.e. higher viral load) included self-reported symptoms and more genes detected, with at most small effects of sex, ethnicity, and age. Single-gene positives almost invariably had Ct &gt; 30, but Cts varied widely in triple-gene positives, including without symptoms. Population-level Cts changed over time, with declining Ct preceding increasing SARS-CoV-2 positivity. Of 6189 participants with IgG S-antibody tests post-first RT-PCR-positive, 4808 (78%) were ever antibody-positive; Cts were significantly higher in those remaining antibody negative.</jats:p></jats:sec><jats:sec id="abs4"><jats:title>Conclusions:</jats:title><jats:p>Marked variation in community SARS-CoV-2 Ct values suggests that they could be a useful epidemiological early-warning indicator.</jats:p></jats:sec><jats:sec id="abs5"><jats:title>Funding:</jats:title><jats:p>Department of Health and Social Care, National Institutes of Health Research, Huo Family Foundation, Medical Research Council UK; Wellcome Trust.</jats:p></jats:sec>

Original publication







eLife Sciences Publications, Ltd

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