Understanding the potential timing of peak viral replication in SARS-CoV-21
A meta-analysis was conducted on 13 studies that evaluated SARS-CoV-2 viral load in serial upper respiratory tract samples, using cycle threshold values. Eight of those studies showed peak viral loads within the first week of symptom onset. Highest viral loads were observed soon after, at symptom onset, or at day 3 to 5 of illness, followed by a consistent decline.
Select study limitations: Most patients received a range of treatments, which may have modified the shedding dynamics. Additionally, this meta-regression analysis identified a substantial heterogeneity among studies (likely due to differences in study population, follow-up, and management approaches). As such, viral replication duration may have been affected. In 8 out of 13 studies, peak is shown between 3 to 5 days after exposure, while in 5 others that evaluated viral load dynamics in lower respiratory tract samples, peak was observed in the second week of illness.
Visualization of peak viral replication early in disease course is for illustrative purposes only, based on a review of multiple published articles. Not drawn to scale.