Beijing [China], Mar 28 : About 3 to 10 per cent of recovered coronavirus patients in China have tested positive again after being discharged from the hospital.
Doctors from Tongji hospital on the frontlines of the outbreak in Wuhan -- where the virus emerged -- told state broadcaster CCTV that they have found no evidence that these patients who again tested positive became infectious, based on close observations of their family members and laboratory tests.
The Chinese mainland, where the disease first emerged last December, has discharged over 90 per cent of its infected patients and around 4,300 confirmed patients are still receiving treatment in hospitals.
The country has reported at least 81,000 cases and more than 3,200 deaths, but most of the new cases have been imported.
The hospital confirmed that five of 147 patients -- only over 3 to five per cent -- tested positive again in nucleic acid tests, according to state broadcaster CCTV.
"So far there is no evidence to suggest that they are infectious," said Wang Wei, the hospital's president.
He said the five patients who tested positive again did not have any symptoms and none of their close contacts had been infected.
In spite of its relatively small sample size, the research of the Tongji hospital, which identified the first COVID-19 case, is especially relevant as China now has far more recovered patients than new confirmed cases.
Wang added that surveillance of similar patients showed that 80 to 90% had no trace of the virus in their system one month after being discharged from the hospital, according to the report.
But, he said, these are just "small samples" and "not enough to assure us of the validity of our initial findings."
"We need a large-scale epidemiological study to guide our disease surveillance and prevention works," Wang said.
Researchers around the world are trying to determine whether recovered patients can still infect people with the coronavirus that causes the disease and if they have developed antibodies offering them immunity to the disease.
Meanwhile, other quarantine facilities in Wuhan have seen about 5 to 10% of their recovered patients test positive again. The findings were reported by the health news outlet Life Times, which is affiliated with state-run newspaper People's Daily.
The studies come as health officials around the world are testing the concept of taking plasma from someone who has been infected, processing it and injecting the antibodies into a sick person to stimulate their immune system.
( With inputs from ANI )