Inferring transmission risk of respiratory viral infection from the viral load kinetics of SARS-CoV-2, England, 2020 to 2021 and influenza A virus, Hong Kong, 2008 to 2012

BackgroundInfectiousness of respiratory viral infections is quantified as plaque forming units (PFU), requiring resource-intensive viral culture that is not routinely performed. We hypothesised that RNA viral load (VL) decline time (e-folding time) in people might serve as an alternative marker of infectiousness.AimThis study's objective was to evaluate the association of RNA<b> </b>VL decline time with RNA and PFU<b> </b>VL area under the curve (AUC) and transmission risk for SARS-CoV-2 and influenza A virus.MethodsIn SARS-CoV-2 and influenza A virus community cohorts, viral RNA was quantified by reverse transcription quantitative PCR in serial upper respiratory tract (URT)-samples collected within households after an initial household-member tested positive for one virus. We evaluated correlations between RNA<b> </b>VL decline time and RNA and PFU-VL AUC. Associations between VL decline time and transmission risk in index-contact pairs were assessed.ResultsIn SARS-CoV-2 cases, we observed positive correlations between RNA<b> </b>VL decline time and RNA and PFU<b> </b>VL AUC with posterior probabilities 1 and 0.96 respectively. In influenza A cases a positive correlation between RNA<b> </b>VL decline time and RNA<b> </b>VL AUC was observed, with posterior probability of 0.87. Index case VL decline times one standard deviation above the cohort-mean showed a relative increase in secondary attack rates of 39% (95%<b> </b>credible interval (CrI):<b> </b>-6.9<b> </b>to<b> </b>95%) for SARS-CoV-2 and 25% (95% CrI:<b> </b>-11 to 71%) for influenza A virus.ConclusionWe identify VL decline time as a potential marker of infectiousness and transmission risk for SARS-CoV-2 and influenza A virus. Early ascertainment of VL kinetics as part of surveillance of new viruses or variants could inform public health decision making.

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Journal
Eurosurveillance
Published
2025-02-13
DOI
https://doi.org/10.2807/1560-7917.es.2025.30.6.2400234
Citations
4
Primary Topic
Respiratory viral infections research
Type
article
Field-Weighted Citation Impact
5.42

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article

Inferring transmission risk of respiratory viral infection from the viral load kinetics of SARS-CoV-2, England, 2020 to 2021 and influenza A virus, Hong Kong, 2008 to 2012

Kieran Madon, Neil M. Ferguson, Robert Varro, Sean Nevin et al.
4 citations
Eurosurveillance
Respiratory viral infections research
5.42
article

Inferring transmission risk of respiratory viral infection from the viral load kinetics of SARS-CoV-2, England, 2020 to 2021 and influenza A virus, Hong Kong, 2008 to 2012

Kieran Madon, Neil M. Ferguson, Robert Varro, Sean Nevin, Seran Hakki, Aleksandra Koycheva, Timesh D Pillay, Emily Conibear, William Barclay, Nieves Derqui, Joe Fenn, Graham P. Taylor, Maria Zambon, Jakob Jonnerby, Shazaad Ahmad, Ajit Lalvani, Jie Zhou, Jake Dunning, Benjamin J. Cowling, Paul S. Freemont, Constanta Luca, Michael A Crone, Rhia Kundu
article en
4 citations

Abstract

BackgroundInfectiousness of respiratory viral infections is quantified as plaque forming units (PFU), requiring resource-intensive viral culture that is not routinely performed. We hypothesised that RNA viral load (VL) decline time (e-folding time) in people might serve as an alternative marker of infectiousness.AimThis study's objective was to evaluate the association of RNA<b> </b>VL decline time with RNA and PFU<b> </b>VL area under the curve (AUC) and transmission risk for SARS-CoV-2 and influenza A virus.MethodsIn SARS-CoV-2 and influenza A virus community cohorts, viral RNA was quantified by reverse transcription quantitative PCR in serial upper respiratory tract (URT)-samples collected within households after an initial household-member tested positive for one virus. We evaluated correlations between RNA<b> </b>VL decline time and RNA and PFU-VL AUC. Associations between VL decline time and transmission risk in index-contact pairs were assessed.ResultsIn SARS-CoV-2 cases, we observed positive correlations between RNA<b> </b>VL decline time and RNA and PFU<b> </b>VL AUC with posterior probabilities 1 and 0.96 respectively. In influenza A cases a positive correlation between RNA<b> </b>VL decline time and RNA<b> </b>VL AUC was observed, with posterior probability of 0.87. Index case VL decline times one standard deviation above the cohort-mean showed a relative increase in secondary attack rates of 39% (95%<b> </b>credible interval (CrI):<b> </b>-6.9<b> </b>to<b> </b>95%) for SARS-CoV-2 and 25% (95% CrI:<b> </b>-11 to 71%) for influenza A virus.ConclusionWe identify VL decline time as a potential marker of infectiousness and transmission risk for SARS-CoV-2 and influenza A virus. Early ascertainment of VL kinetics as part of surveillance of new viruses or variants could inform public health decision making.

EurosurveillanceVol. 30(6)
University of Liverpool (GB), Manchester Academic Health Science Centre (GB), Hong Kong Science and Technology Parks Corporation (HK), University of Oxford (GB), London Biofoundry (GB), NIHR Imperial Biomedical Research Centre (GB), Knowledge Foundation (SE), UK Dementia Research Institute (GB), Health Protection Research Unit in Emerging and Zoonotic Infections at University of Liverpool (GB), UK Health Security Agency (GB), Laboratory of Data Discovery for Health (HK), Imperial College London (GB), University of Hong Kong (HK)
UK Research and Innovation, National Institute for Health Research Health Protection Research Unit, National Institute for Health and Care Research, Department of Health and Social Care, Imperial College London, UK Dementia Research Institute, Medical Research Council, Health and Medical Research Fund, National Institute of Allergy and Infectious Diseases
Openalex Percentile: Top 5%
Respiratory viral infections research
5.42
DOIOpen Access PDFOpenAlex
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