A worker is seen in an area under special management for COVID-19 in Huanggu District, Shenyang, northeast China's Liaoning Province, Jan. 7, 2021. Photo:Xinhua

Wangkui county in Northeast China's Heilongjiang Province has entered lockdown with restrictions on transportation and residential communities after detecting 26 COVID-19 asymptomatic patients on Monday. The outbreak has also spread to the neighboring Jilin Province.  

Anti-epidemic experts said the silent virus carriers have brought a new challenge to China's current epidemic prevention and control work.

As of 8 pm Monday, the city of Suihua, where Wangkui county is located, reported 45 asymptomatic patients and one confirmed COVID-19 patient. A total of 1,299 people have been identified as close contacts and have been quarantined.

All buses and taxis in the county have suspended operations due to the outbreak. Vehicles were not allowed to enter, with the exception of those engaging in epidemic prevention and control work. Highway entries to the county have also been closed. 

All residential communities have now entered closed-management mode. Educational institutions, entertainment venues and private clinics were ordered to close, according to a local government official at a press conference on Monday. 

The reported asymptomatic patients were concentrated in Huiqi village, which has been raised to a medium-risk area for COVID-19. The epidemiological investigation showed that many patients either live in or have visited the village, but the origin of this fresh outbreak still requires further investigation.

Authorities in Suihua have also advised citizens not to go out unless necessary. From Sunday, anyone wishing to leave the city has to present negative nucleic acid test result given within the last three days. 

Asymptomatic patients are a great challenge for China's epidemic prevention and control efforts, as the novel coronavirus has a tendency to become influenza, its infectivity seems stronger than before, and the mortality rate is lower, Zhang Yuexin, a member of Xinjiang's anti-epidemic group, told the Global Times on Monday. 

He said that silent virus carriers are difficult to detect as they show no symptoms, and urged local governments to beef up testing capabilities and roll out regular tests among key populations and regions where epidemic control measures are weak.

The outbreak in Wangkui county has also affected the neighboring province. Changchun, Northeast China's Jilin Province, newly reported four asymptomatic patients, two couples who had recently been to Wangkui. 

The residential communities where they live have been sealed off, with all personnel and vehicles only being allowed in and no one allowed out. 

According to the epidemiological investigation, the patients took trains, buses and taxis on their way back to Changchun. All their close contacts have been tracked and put in isolation. 

Local authorities have begun conducting nucleic acid tests among nearly 15,000 residents in the two sealed-off communities, which are expected to be completed by the end of Monday. As of 12:45 pm Monday, more than 5,000 people had been tested, said Gao Yutang, director of the Changchun Health Commission, at a press conference on Monday. 

Suihua authorities have already shared the information on the 82 people who left the outbreak epicenter since December 20 with neighboring provinces and relevant cities so that the appropriate investigations can be carried out in these places. 

The Chinese mainland reported 85 local COVID-19 confirmed cases and 61 local asymptomatic patients on Monday.