I wanted to share two recent studies that question our understanding of how long SARS-CoV-2 can live in various body specimens, both with and without humans actually displaying symptoms.
Study 1) In Beijing, a small study of 16 mostly young, healthy, male patients showed positive viral PCR throat swabs despite symptoms resolution. Half (8 of 16 patients) remained virus positive even after resolution of symptoms (median 2.5 days, range 1 to 8 days).
Also noted: an Incubation period of 5 days (similar to other studies), and mean symptoms duration 8 days.
Importantly, it is unknown if PCR positivity means that individual is capable of transmission (particularly at such a late stage of illness).
Bottom line: throat swabs may still harbor virus RNA for up to eight days after symptom resolution, but we don’t know if that means those individuals are contagious that late in their sickness.
What does this study tell us? While only a small study, it raises concern for how we develop guidelines to discontinue self isolation when sick (particularly when we are not tested serially for virus presence, as most people are not in the United States).
Study 2) Also in Beijing, viral PCR was tested from multiple body sites (pharyngeal, sputum, feces) in 133 patients throughout their illness. Surprisingly, virus could be identified in the sputum and feces for long after it was not identified in the pharyngeal samples (39 days in sputum and 13 days in feces). As in the previous study, we do not know whether positive results in the sputum or feces poses a risk for infection to others.
What does the study tell us? It raises concern for how we are testing patients to determine resolution of infection. The typical pharyngeal swab that is currently performed may not be sensitive for determining contagious potential. Since this is a small study, we must follow this up in different regions with a larger population before changing our clinical approach.
Reference: Chen C, Gao G, Xu Y, et al. SARS-CoV-2–Positive Sputum and Feces After Conversion of Pharyngeal Samples in Patients With COVID-19. Ann Intern Med. 2020; [Epub ahead of print 30 March 2020]. doi: https://doi.org/10.7326/M20-0991