Renowned epidemiologist Zhong Nanshan said Wednesday that asymptomatic COVID-19 patients will not cause another major outbreak in China, and that the country will not see a significant rebound if the transmission chain is cut off.

“Because we have a strong monitoring system, once (asymptomatic carriers) are discovered, they will be immediately isolated. At the same time, relevant contacts will be immediately quarantined for observation,” Zhong said in an interview with Shenzhen TV.

On Tuesday, the National Health Commission released data on asymptomatic coronavirus carriers for the first time and included them in the total case tally. As of Wednesday, there were 1,075 asymptomatic carriers of the coronavirus that causes COVID-19.

According to the commission, such people — sometimes referred to as silent carriers — do not have the usual symptoms of COVID-19 such as fever, cough, and sore throat. Despite the absence of clinically recognizable symptoms or signs, tests for the coronavirus yield positive results for this group. Moreover, studies suggest they could be just as infectious as sick patients.

Concerns over silent carriers came to light in late January, when sporadic asymptomatic cases were detected from screenings of close contacts of confirmed COVID-19 patients. Though the National Health Commission first acknowledged the phenomenon on Jan. 28, asymptomatic patients were not required to be quarantined and could instead choose to self-isolate at home.

According to the existing data collected and analyzed by Sixth Tone’s sister publication The Paper, there is no clear consensus on the rough proportion of asymptomatic individuals within an infected population. Comparisons among various studies, domestic and abroad, indicate that the proportion of asymptomatic infections can vary greatly depending on the sample.

Iceland, which has the highest rate of coronavirus testing in the world, has a total population of 360,000. Nearly 18,000 people in the country have been tested for COVID-19, and around half of those who were positive were asymptomatic.

In China, if silent carriers develop clinical symptoms, they become “confirmed cases” and are no longer classified as asymptomatic cases.

In another interview with China Global Television Network on Sunday, Zhong said that he doesn’t think there is a large number of asymptomatic patients in China, as they would have infected many others, resulting in more known cases.

“I don’t think at this stage we have a lot of asymptomatic patients,” he said. “If so, these patients would be transmitting (the virus) to other people, making the number higher. But now, actually, it’s going down.”

Editor: Bibek Bhandari.

(Header image: Passengers at a health screening checkpoint at Jinggangshan Airport, Jiangxi province, Feb. 11, 2020. Xinhua)

