Objectives: No studies have examined longitudinal patterns of naturally exhaled SARS-CoV-2 RNA viral load (VL) during acute infection. We report this using facemask sampling (FMS) and assessed the relationship between emitted RNA VL and household transmission. Methods: Between December 2020 and February 2021, we recruited participants within 24 hours of a positive RT-qPCR on upper respiratory tract sampling (URTS) (day 0). Participants gave FMS (for 1 hour) and URTS (self-taken) on 7 occasions up to day 21. Samples were analysed by RT-qPCR (from sampling matrix strips within the mask) and symptom diaries recorded. Household transmission was assessed through reporting of positive URTS RT-qPCR in household contacts. Results: Analysis of 203 FMS and 190 URTS from 34 participants showed that RNA VL peaked in the first five days following sampling. Concomitant URTS, FMS RNA VL and symptom scores however were poorly correlated, but a higher severity of reported symptoms was associated with FMS positivity up to day 5. Of 28 participants who had household contacts, 12 (43%) reported transmission. Frequency of household transmission was associated with the highest (peak) FMS RNA VL obtained (negative copies/strip: 0% household transmission; 1-1000 copies/strip: 20%; 1001 – 10,000 copies/strip: 57%; >10,000 copies/strip: 75%; p=0.048; age adjusted odds ratio of transmission per log increase in copies/strip: 4.97; 95% CI: 1.20-20.55, p=0.02) but this was not observed with peak URTS RNA VL. Conclusions: Exhaled RNA VL measured by FMS is highest in early infection, can be positive in symptomatic patients with concomitantly negative URTS and is strongly associated with household transmission.

Fuente: Clinical Microbiology and Infection
Available online 14 July 2022