What does viral load mean for COVID patients?

Viral load and severity of COVID-19

A paper published in the Lancet on 19th March demonstrates a link between viral load and disease severity in COVID-19.  Nasopharyngeal aspirates from a group of 76 patients with confirmed COVID-19 were studied. Analysis found that mean viral load of the samples was around 60 times higher in patients who developed severe disease features such as respiratory distress, hypoxia or complications (respiratory failure, septic shock, organ failure). Studies of serial samples in 31 cases found clearance of the virus within 10 days in mild cases, with all 10 severe cases having persistence of the virus beyond 10 days. 

The figure above, titled by the paper authors as “Viral dynamics in patients with mild and severe COVID-19” demonstrates statistically significant differences in viral loads between mildly and severely affected patients, and persistence of detection of virus later in disease course for severe cases.


Liu Y et. al. Viral dynamics in mild and severe cases of COVID-19. Lancet Infect. Dis. March 2020. Available from: https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30232-2/fulltext [accessed 24/3/20].

This article was written by Dr Rachel Coles on 24th March 2020

Please email covid@medshr.net with any comments or queries.

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