From: SARS-CoV-2 viral load is associated with risk of transmission to household and community contacts
Characteristic | Unadjusted RR (95% CI) | p-value | Adjusted RR* (95% CI) | p-value |
---|---|---|---|---|
Index case viral load at time of test (log10 RNA copies per mL of saliva) | 1.25 (1.06–1.46) | 0.007 | 1.27 (1.22–1.32) | p < 0.001 |
Time between index case test and exposure (days) | 1.12 (1.10–1.15) | p < 0.001 | 1.14 (1.11–1.17) | p < 0.001 |
Age of case (years) | 0.99 (0.94–1.04) | 0.7 | – | – |
Case comorbidities | 0.89 (0.45–1.74) | 0.7 | – | – |
Symptomatic status on day of exposure | ||||
 Asymptomatic | Reference | – | – | – |
 Pre-symptomatic | 2.23 (1.00–4.97) | 0.05 | – | – |
 Symptomatic | 2.05 (0.94–4.48) | 0.07 | – | – |
 Case had cough on day of exposure | 1.85 (1.15–2.99) | 0.01 | 1.41 (1.04–1.92) | 0.03 |
 Case congested or with runny nose on day of exposure | 1.46 (0.94–2.29) | 0.09 | – | – |
Mask use | ||||
 No masks used | Reference | – | – | – |
 Case and/or contact wore a mask | 1.02 (0.59–1.78) | 0.9 | – | – |
Duration (min) | Â | Â | Â | Â |
 < 30 | Reference | – | – | – |
 ≥ 30 | 1.61 (0.84–3.09) | 0.1 | – | – |
Location | Â | |||
 Outdoor | Reference | – | – | – |
 Indoor | 2.39 (0.69–8.24) | 0.2 | – | – |
Contact type | ||||
 Non-physical contact | Reference | – | – | – |
 Physical contact | 2.14 (1.34–3.44) | 0.001 | 1.78 (1.26–2.53) | 0.001 |
Contact relationship | ||||
 Household | Reference | – | – | – |
 Non-household | 1.19 (0.77–1.83) | 0.4 | – | – |