New research found that half of the patients treated for mild Covid-19 still had the infection in their system a week after symptoms disappeared.
The study was based on 16 patients who tested positive for coronavirus at the Treatment Center of PLA General Hospital in Beijing, China, between January 28 and February 9.
Researchers collected samples from throat swabs taken from all patients – who had an average age of 35.5 – on alternate days before analysing them.
Patients were discharged after recovering from coronavirus and confirmed as being negative by at least two consecutive polymerase chain reaction (PCR) tests.
Professor Lokesh Sharma, who co-authored the paper, from the Yale School of Medicine, said: “The most significant finding from our study is that half of the patients kept shedding the virus even after resolution of their symptoms.
“More severe infections may have even longer shedding times.”
The main symptoms included fever, cough, difficulty breathing and a sore throat, according to the research letter published in the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine.
Scientists said the incubation period was five days in all but one patient, while the average duration of symptoms was eight days.
Meanwhile, they found that the length of time patients remained contagious after their symptoms ceased ranged from one to eight days.
Two of the patients had diabetes and one had tuberculosis – neither of which affected the timing of the course of the infection, they said.
Based on their findings, Dr Lixin Xie, a professor of College of Pulmonary and Critical Care Medicine at the hospital in Beijing, advised those who had tested to positive to extend their self-isolation for another two weeks – even after recovery.
He said: “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.”
