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Volume 7, Issue 2

The ratio between SARS-CoV-2 RNA viral load and culturable viral titre differs depending on the stage of infection: a case study of household transmission in an adult male Open Access

Abstract

Effective public health measures for communicable diseases rely on the ability to identify infectious individuals and prevent transmission from those individuals. For severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the presence of replication-competent virus in specimens from an individual is the gold standard for confirming infectiousness. However, viral culture from clinical specimens is difficult and infrequently performed. Instead, infectiousness may be inferred based on the abundance of viral RNA (or viral load) in a specimen, which is more easily assessed. For this reason, understanding the relationship between RNA viral load and infectious viral titre has important implications for public health strategy. In this case report, we quantified incident, longitudinal SARS-CoV-2 viral loads collected from saliva and nasal-swab specimens, and viral titre from nasal-swab specimens. We observed that the relationship between viral load and viral titre decreases by over five orders of magnitude throughout the course of the infection. Our work demonstrates the potential for infectious virus even in specimens with low viral loads collected during the early phases of infection.

  • Received:
  • Accepted:
  • Published Online:
Keyword(s): culture , incident , infectivity , longitudinal and SARS-CoV-2
Funding
This study was supported by the:
  • National Institutes of Health (NIH) (Award F30AI167524)
    • Principal Award Recipient: AlexanderViloria Winnett
  • Foundation for the National Institutes of Health (Award AI151698)
    • Principal Award Recipient: MichaelGale, Jr
  • David Geffen School of Medicine, University of California, Los Angeles
    • Principal Award Recipient: AlexanderViloria Winnett
  • Jacobs Institute, California Institute of Technology
    • Principal Award Recipient: RustemF. Ismagilov
  • Ronald and Maxine Linde Center for New Initiatives, California Institute of Technology
    • Principal Award Recipient: RustemF. Ismagilov
  • Bill and Melinda Gates Foundation (Award INV-023134)
    • Principal Award Recipient: RustemF. Ismagilov
© 2025 The Authors
  • This is an open-access article distributed under the terms of the Creative Commons Attribution License.
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2025-02-17
2026-03-07

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/content/journal/acmi/10.1099/acmi.0.000732.v3
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The ratio between SARS-CoV-2 RNA viral load and culturable viral titre differs depending on the stage of infection: a case study of household transmission in an adult male
Access Microbiology 7, 000732.v3 (2025); https://doi.org/10.1099/acmi.0.000732.v3
/content/journal/acmi/10.1099/acmi.0.000732.v3
/content/journal/acmi/10.1099/acmi.0.000732.v3
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