Chinese experts express concerns over rise in asymptomatic coronavirus carriers

People wearing face masks exit a subway station in Beijing on March 30, 2020.
People wearing face masks exit a subway station in Beijing on March 30, 2020.PHOTO: REUTERS

BEIJING (CHINA DAILY/ASIA NEWS NETWORK) - Some Chinese medical experts are calling for more measures to contain the spread of asymptomatic Covid-19 cases as more such cases have been reported across China.

The health commission of Henan province reported on Sunday (March 29) that a female patient confirmed on Saturday was a close contact of an asymptomatic virus carrier, a doctor working for Jiaxian County People's Hospital.

The two shared a vehicle and dined three times together on March 21 before she developed symptoms on March 24.

The Henan health commission later found that one of the doctor's colleagues had travelled to Wuhan, Hubei province, and passed a 14-day quarantine. So far, three doctors from the hospital have tested positive for coronavirus while showing no symptoms during a physical examination for medical workers.

In addition, imported asymptomatic carriers have been reported in Dezhou, Shandong province, Guiyang, Guizhou province, and Mianyang, Sichuan province.

Jiaxing, Zhejiang province, reported last Thursday that a confirmed case was infected by an asymptomatic carrier on a plane.

The health commission of Gansu province issued a regulation on Sunday to strengthen the monitoring of asymptomatic carriers, ordering that people from Hubei must test negative twice for the coronavirus before resuming work.

The move came after a person from Hubei tested positive for the virus on Saturday. The case raised concerns because the patient possessed a "green code", a QR code issued in Hubei indicating that a traveller is healthy.

China's top medical experts have warned that more measures should be taken to tackle the spread of the virus related to asymptomatic cases. However, some of them said that the public has no reason to panic.

Dr Zeng Guang, chief epidemiologist at the Chinese Centre for Disease Control and Prevention, said that China's prevention measures have proved to be effective despite the existence of asymptomatic sufferers.

"Though asymptomatic cases haven't been listed as confirmed cases, that doesn't mean that we don't pay attention to them," Dr Zeng said. "We have confidence in the prevention of further spreading by asymptomatic carriers."


Dr Zhong Nanshan, one of China's most renowned experts in respiratory diseases, reinforced Dr Zeng's view during an interview with China Central Television in which he said that the disease's curve and the current mortality rate suggested that the number of undetected asymptomatic carriers is unlikely to be large in the country.

Dr Zhong said in an interview with CGTN on Sunday that the infectivity of asymptomatic infections could be fairly high, and one asymptomatic patient could infect up to 3.5 persons.

But he added that the newly confirmed cases of Covid-19 infection has not increased, but declined, indicating that China does not have a large number of asymptomatic patients.

According to Global Times, a recent study showed the infectivity of asymptomatic patients could be nearly the same as confirmed cases.

Scientists with the Ningbo Centre for Disease Control and Prevention in East China's Zhejiang Province recently found that 6.3 per cent of confirmed cases' close contacts were ultimately infected with the virus. The percentage for asymptomatic patients' close contacts was 4.4 per cent.

Containing asymptomatic carriers has long been included in China's disease control plans. A plan issued on Jan 28 stated that such carriers, though not classified as confirmed Covid-19 cases, would be "strictly monitored and put under a 14-day quarantine".


The quarantine would continue if the carriers failed to pass two coronavirus tests. They would be hospitalised immediately if they develop any symptoms, according to the plan.

The public should pay attention to any discomfort, including cough, fatigue and sore throat, and strengthen self-protection such as wearing masks, according to Lu Jinxing, an official at the Chinese CDC.

"Hospitals should also strengthen the monitoring of such patients and trace close contacts to find asymptomatic carriers," he said.

No official data on the overall number of asymptomatic patients has been reported by Chinese health authorities. They are not counted as "confirmed cases," according to the Chinese National Health Commission.

But Dr Yang Zhanqiu, a Wuhan-based virologist, told the Global Times on Sunday that there may be an estimation of at least 200,000 virus carriers with no symptoms currently in China.

The asymptomatic patients have strong physical immunity or carry weak virus with less virulence, which is why they don't show symptoms but they still spread the virus in the early stage of infection, Dr Yang explained.