Coronavirus still detectable in sputum and stool after throat swabs become negative
1 April 2020
New data suggests that people with COVID-19 may still test positive for coronavirus in their stool and sputum, even after pharyngeal swabs have become negative for the virus.
Given that quarantine of infected people is critical to containment of COVID-19, it’s important to have certainty around how long a person might be infectious.
Pharyngeal swabs are widely used to decide if a patient can be discharged from hospital or can be released from isolation or quarantine. So, it’s important to know if patients are truly free of the virus or whether they are still shedding virus particles, and whether these particles are capable of infecting others.
This study analysed 133 patients admitted to hospital in China with COVID-19. The patients were initially diagnosed as having COVID-19 by real-time PCR testing of pharyngeal swabs. PCR testing detects the genetic material of the SARS-CoV-2 virus in a sample.
Of those people, the researchers identified 22 patients who had tested positive for sputum or stool samples while having negative pharyngeal swabs.
Sputum samples in these patients remained positive for virus up to 39 days after their pharyngeal swabs were negative.
Stool samples remained positive for 13 days after the pharyngeal swabs were negative.
The authors of the study suggest further research is needed into the infectious risk of patients who are deemed to have recovered and who are discharged.
Last Reviewed: 01/04/2020
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. [Letter]. Ann Intern Med. 2020; [Epub ahead of print 30 March 2020]. doi: https://doi.org/10.7326/M20-0991