Beijing, March 28 : Amid the fast-spreading coronavirus (COVID-19) pandemic, researchers, including one of Indian-origin, have found that half of the patients they treated for mild COVID-19 infection still carried the coronavirus pathogen for up to eight days after symptoms disappeared.
Researchers suggest extending quarantine for at least two more weeks even after recovery, just to be on the safe side.
In a study, published in the American Journal of Respiratory and Critical Care Medicine, researchers picked 16 patients with COVID-19, who were treated and released from the Treatment Center of PLA General Hospital in Beijing, China between January 28 and February 9.
Patients studied had a median age of 35.5 years.
"The most significant finding from our study is that half of the patients kept shedding the virus even after resolution of their symptoms," said study co-lead author Lokesh Sharma from Yale University in the US.
"More severe infections may have even longer shedding times," Sharma added.
For the findings, researchers collected samples from throat swabs taken from all patients on alternate days and analysed.
Patients were discharged after their recovery and confirmation of negative viral status by at least two consecutive polymerase chain reaction (PCR) tests.
According to the study, the primary symptoms in these patients included fever, cough, pain in the pharynx (pharyngalgia) and difficult or laboured breathing (dyspnea).
Patients were treated with a range of medications.
The time from infection to onset of symptoms (incubation period) was five days among all but one patient, the study said.
The average duration of symptoms was eight days, while the length of time patients remained contagious after the end of their symptoms ranged from one to eight days.
Two patients had diabetes and one had tuberculosis, neither of which affected the timing of the course of COVID-19 infection.
"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," recommended corresponding author Lixin Xie from Chinese PLA General Hospital in China.
The authors had a message for the medical community: "COVID-19 patients can be infectious even after their symptomatic recovery, so treat the asymptomatic/recently recovered patients as carefully as symptomatic patients."
The researchers emphasised that all of these patients had milder infections and recovered from the disease and that the study looked at a small number of patients.
They noted that it is unclear whether similar results would hold true for more vulnerable patients such as the elderly, those with suppressed immune systems and patients on immunosuppressive therapies.
"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," Xie added.