An interesting article published by Owusu in the Journal of Infectious Diseases 27th February 2021 looked at this issue.
They collected serial nasopharyngeal specimens at various time points from 109 individuals with PCR confirmed COVID-19.
They calculated the probability of viral RNA shedding resolution using the Kaplan-Meier estimator and evaluated characteristics associated with shedding resolution using a Cox proportional hazards regression.
They attempted viral culture for 35 PCR positive nasopharyngeal specimens collected greater than or equal to 10 days after symptom onset.
The study found that the likelihood of viral RNA shedding resolution at 10 days after symptom onset was approximately 3%.
Time to shedding resolution was shorter amongst participants who were younger than 18 years old and longer amongst those aged greater than or equal to 50 as compared to participants who were aged 18 to 49.
In these PCR swabs, there was no replication competent viruses recovered.
The study concluded although most patients were positive for SARS-CoV-2 after or on 10 days after symptoms onset, the study suggested that individuals with mild to moderate COVID-19 were unlikely to be infectious 10 days after symptoms onset.
Dr Paul Ettlinger
BM, DRCOG, FRCGP, FRIPH, DOccMed