The coronavirus would stay longer in the body of severely ill patients

The SARS-CoV-2 pandemic has already contaminated more than 2.5 million people in the world. To stem theepidemic and therefore the contagiousness of carriers, it is essential to know how the viral load in infected patients. A recent study published in the British Medical Journal gives some leads that will need to be confirmed.

Its objective was to assess the progression of viral load as a function of the severity of the disease. 96 patients were admitted to the data analysis, 74 severe cases and 22 moderate. The sample is small and disproportionate, which can lead to possible biases. Over 3,497 different samples (mucus, stool, serum, urine) were collected from the patients. Here is what scientists have observed and what they conclude from it.

Viral load and severity of the disease

First, the patients in this cohort suffering from a severe form of the disease keep the virus longer in their organism (duration median at 21 days) than moderate cases (median duration 14 days). Then the peak of the viral load, that is to say the time when it peaks because the virus replicates enormously, also lasts longer in these patients.

Indeed, the peak is observed during the second week in moderate cases, then fades while it remains high during the third week of the disease in severely affected patients. Finally, the authors note that the virus is present for a much longer duration in stool of patients (median duration of 22 days) than in their secretions respiratory (median duration of 18 days), regardless of gravity of the disease.

What should we think of these observations?

They must be taken for what they are, that is to say, observations. The study has limitations, notably the fact that it is not multicentric and that sample size is insufficient. The authors recognize this themselves: " This can lead to an unbalanced distribution of confounding factors when assessing viral shedding and viral load. " Then, the viral load is influenced by many factors.

The quality of the samples taken directly affects viral load, so the study of viral load only partially reflects the amount of virus in the body. Finally, PCR tests cannot distinguish between a viable virus and a non-viable virus, and does not reflect the level of replication virus in different tissues. We must therefore be careful with these preliminary results and not draw hasty conclusions from them.