China remains vigilant for new cases

The National Health Commission reported 30 new confirmed cases on the Chinese mainland, including five locally transmitted cases, and 47 new asymptomatic infections on Saturday, as efforts to curtail a second wave of infections have intensified nationwide.

All of the five domestic infections were detected in the southern province of Guangdong, and they contracted the virus from people who had been infected from outside of the country, according to the provincial government of Guangdong.

Wang Bin, a senior official at the National Health Commission's disease prevention and control bureau, said last week that such cases were often close-contacts of imported infections who transmit the virus to others during transit or self-isolation at home.

The remaining 25 confirmed cases involved travelers from abroad, up from 18 imported cases the previous day and bringing the total number of infections entering from overseas to 913 as of Saturday, commission data shows.

To stamp out the risk of infected inbound travelers, local governments across the country have stepped up monitoring of incoming passengers and imposed centralized medical observation on all of them.

Of the 47 new asymptomatic individuals－people who are infected but show no symptoms－16 were travelers from abroad, according to the commission. As of Saturday, 1,024 symptom-free patients were under medical observation nationwide, with about two-thirds of them in Hubei province, the hardest-hit region in China.

To fend off new outbreaks, Wang Chen, president of the Chinese Academy of Medical Sciences, has called for science-based, prompt and refined epidemiological research that can supplement essential knowledge about the virus.

"In severely stricken areas, nucleic acid testing can help identify undetected asymptomatic cases and antibody tests will reveal the overall immunity levels of the population," he told People's Daily on Saturday.

Wu Zunyou, chief epidemiologist at the Chinese Center for Disease Control and Prevention, said earlier that confirmed cases associated with asymptomatic infections account for less than 5 percent of all infections, citing a study conducted by the disease control center in Ningbo, Zhejiang province.

"Swift detection and control of asymptomatic infections will reduce their risks of triggering another outbreak to the minimum, and wide spread of the virus is unlikely," he said.

Even though the asymptomatic group is believed to be small and unable to cause widespread transmission, authorities are implementing strict screening and quarantine measures for them.

The National Health Commission started to report the number of asymptomatic cases as a separate category in its daily briefings on April 1, and it has stressed several times that the reporting and investigation of asymptomatic cases, and management of their close contacts, should be consistent with that of confirmed infections, including 14 days of centralized quarantine and multiple nucleic acid tests before release.

Pushing beyond the national requirement, Hainan and Zhejiang provinces have recently decided to extend the isolation period－adding 14 more days of quarantine at designated facilities following 14 days at hospitals－for asymptomatic cases, according to provincial health authorities.

Fujian province announced last week that asymptomatic individuals will undergo 14-day self-isolation and monitoring of health status after completing the first round of quarantine, and that they are required to visit hospitals for checkups at the second and fourth week after being discharged, Fujian Daily reported.