A new analysis of patients with covid-19 in China published by The BMJ today shows that the virus persists longer and peaks later in the respiratory tissue of patients with severe disease, compared with patients with mild disease.
Researchers estimated viral loads in more than 3,000 samples collected from 96 patients with covid-19 infection admitted to a hospital in Zhejiang province, China between 19 January and 20 March 2020.
The viral load is the number of viral particles present in an infected patient. In general, the higher the viral load the more virus particles a patient can release (“shed”) into their environment when they exhale or cough.
The researchers found that the median duration of virus in stool (22 days) was significantly longer than in respiratory (18 days) and blood samples (16 days).
They also found that the median duration of virus in the respiratory samples of patients with severe disease (21 days) was significantly longer than in patients with mild disease (14 days).
In the mild group, the viral loads peaked in respiratory samples in the second week from disease onset, whereas viral load continued to be high during the third week in the severe group.
Virus duration was longer in patients older than 60 years and in men.
They point to some study limitations, such as the relatively small number of participants, that may have affected the accuracy of their results. However, they say their findings show that the virus persists longer with higher load and peaks later in the respiratory tissue of patients with severe disease.
The findings also highlight the importance of carrying out strict management during each stage of severe disease to help prevent and control the epidemic, they conclude.