Are COVID-19 Patients Contagious After Symptoms?

New research from the American Thoracic Society warns that patients who have recovered from the novel COVID-19 infection could remain contagious for up to eight days after symptoms have vanished. Researchers found that around half of patients treated for mild cases of COVID-19 still had traces of the virus in their systems, despite having no symptoms.

"COVID-19 patients can be infectious even after their symptomatic recovery, so treat the asymptomatic/recently recovered patients as carefully as symptomatic patients," warns the report.

Virus shedding continues after resolution of symptoms

The findings were published online in the American Journal of Respiratory and Critical Care Medicine, with co-lead author Dr. Lokesh Sharma saying, "The most significant finding from our study is that half of the patients kept shedding the virus even after resolution of their symptoms." He adds that in more severe cases, the shedding times could be even longer.

Titled "Time Kinetics of Viral Clearance and Resolution of Symptoms in Novel Coronavirus Infection," the report analysed Chinese patients with a median age of 35.5 years. The team collected throat swab samples taken throughout the infection period and found that even after symptoms had disappeared, 50% of patients remained contagious. For this reason, the team stress self-isolating for an additional two weeks after symptoms have disappeared is essential to avoid passing on traces of the virus to others.

Experts recommend extending quarantine

"If you had mild respiratory symptoms from COVID-19 and were staying at home so as not to infect people, extend your quarantine for another two weeks after recovery to ensure that you don't infect other people," says Dr. Lixin Xie, MD, corresponding author of the study. “Further studies are needed to investigate if the real-time PCR-detected virus is capable of transmission in the later stages of COVID-19 infection,” adds Dr. Xie.  

The risks of unknowingly spreading COVID-19 don't just apply to recovered patents, with another new study suggesting that the highest levels of contagion could occur one to two days before symptoms appear. In more than four out of 10 cases, symptoms may not appear at all.

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