A number of coronavirus patients in mainland China have tested positive for infection after earlier being cleared, according to official figures, though medical experts say it is unlikely they were infected twice and have warned against releasing people from hospital prematurely.
As of Tuesday, the virus had infected more than 80,000 people in mainland China, of whom more than 47,000 had been released from hospital, official data showed.
They were released after being getting a negative result in a reverse transcriptase-polymerase chain reaction (PCR) test – the most commonly used when testing for infection – but then tested positive again days or even weeks later.
On Monday, two people in the northern port city of Tianjin, where more than 130 cases have been confirmed, were sent back to hospital after testing positive for Covid-19 about a week after being told they had recovered from it. An earlier case involved a patient who tested positive for the disease two weeks after being sent home, the local health authority said.
In south China’s Guangdong province, 14 per cent of coronavirus patients released from hospital were later found to still be infected, the provincial disease control centre said last week.
Similar cases have been reported in other parts of the country, including Jiangsu and Sichuan provinces
Why are people testing positive twice?
“It’s not that these people get a second infection, or a persistent infection, as some worried,” said Professor Jin Dongyan, a molecular virologist from the Li Ka Shing Faculty of Medicine at the University of Hong Kong.Prevention magazine Subscription
It was either because the tests were not done properly in the first place, or the patient was undergoing a long course of the disease, he said.
Various factors could cause the test results to be inaccurate, including the quality of the test kit and the way the sample was collected and stored, Jin said.
Under China’s testing criteria, people can be released from hospital if their body temperature is normal for three days, they have no respiratory problems, and the chest lesions shown on the computed tomography have significantly improved. They must also test negative in two consecutive negative PCR tests at least one day apart.
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