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Factors associated with prolonged viral RNA shedding in patients with COVID-19

Our take —

Among 113 symptomatic COVID-19 patients in two hospitals outside of Wuhan, China, the median duration of viral RNA shedding was 17 days. Risk factors for prolonged viral shedding were identified as male sex, delayed hospital admission, and invasive mechanical ventilation, though given the small sample size and possible confounding (e.g. disease severity), results should be interpreted cautiously. An important consideration is that viral RNA shedding does not necessarily imply infectiousness. Someone could be infectious for a shorter or longer duration, and more research is needed on this subject.

Study design

Retrospective Cohort

Study population and setting

A total of 113 patients with symptomatic SARS-CoV-2 infection from two hospitals outside of Wuhan were included in this study. Patients were admitted between January 13, 2020 and February 19, 2020. The purpose of this study was to examine the duration of viral RNA shedding, and identify risk factors of prolonged viral shedding. Patients were included in this study if they had been under observation for at least 21 days. Treatment, outcomes, and clinical characteristics were all obtained from electronic medical records, and duration of viral shedding was defined as days from symptom onset to three persistent negative specimens (the first of these defining the end of viral shedding).

Summary of Main Findings

In this sample, the median duration of RNA detection was 17 days (IQR: 13-22) from symptom onset. Prolonged viral shedding was defined as greater than or equal to 15 days. 70% of the sample met the criteria for prolonged viral shedding (79/113). Factors independently associated with prolonged viral shedding were male sex, delayed hospital admission, and invasive mechanical ventilation.

Study Strengths

This study was able to capture clinical characteristics, treatment, and outcome data from electronic medical records in order to identify independent risk factors associated with prolonged viral RNA shedding.


Given the small sample size, the study was underpowered for multivariable modeling. Factors included in the final model looking for independent risk factors were only those found to be significant in univariate analyses, and thus there is a possibility of residual confounding – namely that some of the differences observed may be explained by factors not included in the model (for example ventilation may be a marker of disease severity). All patients received the same antiviral treatment, meaning that there was no way to determine whether the duration of viral RNA shedding was in part due to the treatment received. Samples collected on those who received mechanical ventilation were taken from the lower respiratory tract, while for those not on mechanical ventilation were collected from sputum, meaning that there may be some bias introduced when comparisons were made between those who received ventilation and those who did not.

Value added

These data on the duration of and factors associated with prolonged viral RNA shedding may help inform clinical management and put into place data-driven practices that mitigate transmission of the disease.