Symptoms predicting the onset and duration of SARS-CoV-2 infectiousness: a community cohort study
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
Introduction
Upper respiratory tract (URT) SARS-CoV-2 viral load (VL) kinetics influence the clinical course of COVID-19, but their relationship to symptoms remains poorly understood. We hypothesised that VL kinetics affect the timing, intensity, and duration of symptoms in community cases.
Methods
Our prospective community cohort provided daily URT swabs for VL quantification for 2 weeks and symptom diaries for 28 days post-recruitment. Symptom data were summarised using a composite Symptom Burden Score (SBS) incorporating symptom presence and severity. Only cases who enrolled sufficiently early post-exposure to discern peak (p)VL were included (n=89). Infectious viral shedding was assessed in a subset (n=37) through quantitative viral culture.
Results
The day of pVL correlated with the day of peak symptom burden score (pSBS) (p<0.001, n=89). Very high pVL (>170,000,000 RNA copies/ml) was linked to prolonged illness, with a subset experiencing symptoms ≥3 weeks (p<0.001). Cases reported more symptoms, as well as an increase in URT symptom burden, on the first day of virus cultivability compared to the preceding day (p<0.001 and p=0.005, n=31). Peak systemic symptom score, and specifically muscle aches, significantly associated with prolonged infectious viral shedding (p=0.012 and p=0.033, n=34). URT symptoms such as rhinitis, sore throat, and hoarse voice showed the steepest increase at infectiousness onset.
Conclusions
The timing of pSBS aligns with pVL, and pVL above 170,000,000 RNA copies/ml predicts prolonged symptom duration. URT symptom escalation often marks the onset of infectiousness, while systemic symptoms, particularly muscle aches, signal prolonged infectiousness. These findings identify symptom-based markers of infectiousness with implications for testing strategies. They also highlight the importance of collecting early, frequent longitudinal symptom and virological data as a core element of the public health response to novel pathogens and future pandemics.
Upper respiratory tract (URT) SARS-CoV-2 viral load (VL) kinetics influence the clinical course of COVID-19, but their relationship to symptoms remains poorly understood. We hypothesised that VL kinetics affect the timing, intensity, and duration of symptoms in community cases.
Methods
Our prospective community cohort provided daily URT swabs for VL quantification for 2 weeks and symptom diaries for 28 days post-recruitment. Symptom data were summarised using a composite Symptom Burden Score (SBS) incorporating symptom presence and severity. Only cases who enrolled sufficiently early post-exposure to discern peak (p)VL were included (n=89). Infectious viral shedding was assessed in a subset (n=37) through quantitative viral culture.
Results
The day of pVL correlated with the day of peak symptom burden score (pSBS) (p<0.001, n=89). Very high pVL (>170,000,000 RNA copies/ml) was linked to prolonged illness, with a subset experiencing symptoms ≥3 weeks (p<0.001). Cases reported more symptoms, as well as an increase in URT symptom burden, on the first day of virus cultivability compared to the preceding day (p<0.001 and p=0.005, n=31). Peak systemic symptom score, and specifically muscle aches, significantly associated with prolonged infectious viral shedding (p=0.012 and p=0.033, n=34). URT symptoms such as rhinitis, sore throat, and hoarse voice showed the steepest increase at infectiousness onset.
Conclusions
The timing of pSBS aligns with pVL, and pVL above 170,000,000 RNA copies/ml predicts prolonged symptom duration. URT symptom escalation often marks the onset of infectiousness, while systemic symptoms, particularly muscle aches, signal prolonged infectiousness. These findings identify symptom-based markers of infectiousness with implications for testing strategies. They also highlight the importance of collecting early, frequent longitudinal symptom and virological data as a core element of the public health response to novel pathogens and future pandemics.
Date Acceptance
2026-02-05
Citation
International Journal of Infectious Diseases
ISSN
1201-9712
Publisher
Elsevier
Journal / Book Title
International Journal of Infectious Diseases
Copyright Statement
Copyright © 2026 Copyright Owner. This is the author’s accepted manuscript made available under a CC-BY licence in accordance with Imperial’s Research Publications Open Access policy (www.imperial.ac.uk/oa-policy)
License URL
Publication Status
Accepted
Article Number
108471
Date Publish Online
2026-02-09