Patients Who Continue To Shed Virus Puzzle Experts

Dressed in a hazmat suit, two masks and a face shield, Du Mingjun knocked on the mahogany door of a flat in a suburban district of Wuhan on a recent morning.

A man wearing a single mask opened the door a crack and, after Du introduced herself as a psychological counsellor, burst into tears.

"I really can't take it anymore," he said. Diagnosed with the novel coronavirus in early February, the man, who appeared to be in his 50s, had been treated at two hospitals before being transferred to a quarantine centre set up in a cluster of apartment blocks in an industrial part of Wuhan.

Why, he asked, did tests say he still had the virus more than two months after he first contracted it?

The answer to that question is a mystery baffling doctors on the frontline of the mainland’s battle against Covid-19, even as it has successfully slowed the spread of the coronavirus across the country.

Chinese doctors in Wuhan, where the virus first emerged in December, say a growing number of cases in which people recover from the virus, but continue to test positive without showing symptoms.

Those patients all tested negative for the virus at some point after recovering, but then tested positive again, some up to 70 days later, the doctors said. Many have done so over 50-60 days.

The prospect of people remaining positive for the virus, and therefore potentially infectious, is of international concern, as many countries seek to end lockdowns and resume economic activity as the spread of the virus slows.

Currently, the globally recommended isolation period after exposure is 14 days.

So far, there have been no confirmations of newly positive patients infecting others, according to mainland health officials.

Beijing has not published precise figures for how many patients fall into this category. But disclosures by Chinese hospitals, as well as in other media reports, indicate there are at least dozens of such cases.

In South Korea, about 1,000 people have been testing positive for four weeks or more. In Italy, health officials noticed that coronavirus patients could test positive for the virus for about a month.

As there is limited knowledge available on how infectious these patients are, doctors in Wuhan are keeping them isolated for longer.

Zhang Dingyu, president of Jinyintan Hospital, where the most serious coronavirus cases were treated, said health officials recognised the isolations may be excessive, especially if patients proved not to be infectious. But, for now, it was better to do so to protect the public, he said.

Yuan Yufeng, a vice president at Zhongnan Hospital in Wuhan, said he was aware of a case in which the patient had positive retests after first being diagnosed with the virus about 70 days earlier.

"We did not see anything like this during Sars,” he said, referring to the 2003 Severe Acute Respiratory Syndrome outbreak that infected 8,098 people globally, and devastated Hong Kong.

Experts and doctors struggle to explain why the virus behaves so differently in these people.

Some suggest that patients retesting as positive after previously testing negative were somehow reinfected with the virus. This would undermine hopes that people catching Covid-19 would produce antibodies that would prevent them from getting sick again from the virus.

Zhao Yan, a doctor of emergency medicine at Wuhan's Zhongnan Hospital, said he was sceptical about the possibility of reinfection based on cases at his facility, although he did not have hard evidence.

"They're closely monitored in the hospital and are aware of the risks, so they stay in quarantine. So I'm sure they were not reinfected."

As could be seen in Wuhan, the virus can also inflict a heavy mental toll on those caught in a seemingly endless cycle of positive tests.

Patients need to stay at the centre for at least 28 days and obtain two negative results before being allowed to leave. Patients are isolated in individual rooms they said were paid for by the government.

The most concerning case facing Du during the visit was the man behind the mahogany door; he had told medical workers the night before that he wanted to kill himself.

His grandson missed him after being gone for so long, he said, and he worried his condition meant he would never be able to see him again.

He broke into another round of sobs. "Why is this happening to me?" (Reuters)