A medical worker conducts a nucleic acid test on a boy in Dalian, Northeast China's Liaoning Province on December 23, 2020. Photo: VCG

Among the 41 "COVID-19 medium-risk areas," there are 13 in Shenyang and 16 in Dalian, two key cities in Northeast China's Liaoning Province, according to health authorities on Sunday. 

Super spreaders have emerged in both cities, said experts, warning the public to remain alert as the current situation is complicated, even as authorities continuously strengthen COVID-19 prevention and control measures. 

On Sunday, Shenyang, Liaoning Province's capital reported three new confirmed cases, bringing the total number of people infected to 25 since December 23.

According to the Health Commission of Shenyang, the first case in the current outbreak has been linked to a traveler surnamed Yin from South Korea. Yin was diagnosed with COVID-19 on December 23, 10 days after he was released from the quarantine. Two days before he was diagnosed, Yin had visited Pukang Hospital four times for treatment. 

Shenyang's Huanggu district health bureau has imposed administrative penalties on Pukang hospital and Huanggu Xiushui outpatient department for failing to take effective epidemic control measures, leading to the spread of the outbreak. 

The Global Times found that as of Saturday, 21 of Yin's close contacts had contracted the disease, 12 are related with the Pukang Hospital and others include Yin's relatives and neighbors. 

A COVID-19 "super-spread event" has also appeared in the port city of Dalian. One of the confirmed cases, surnamed Jin, had infected 11 people during a family gathering, and the virus then spread to neighbors and other close contacts, causing 33 people to be infected, said Zhao Lian, deputy director of the Dalian Health Commission at a Sunday press conference.

A locally infected COVID-19 case was also found in Dalian on Saturday, bringing the number of confirmed COVID-19 patients to 48 plus 30 asymptomatic local infected persons who are under medical observation, the local authority announced.

According to Zhao, the outbreak in Dalian has extended beyond the city's cold chain zone to communities, shopping malls, schools and hospitals. The virus' fast transmission has infected people from different walks of life. 

Both Shenyang and Dalian have entered "wartime" mode. According to local authority, as of Sunday, nine districts in Shenyang have carried out over 6 million nucleic acid tests, with 4.5 million people tested negative for coronavirus.  

The city has locked down a three-kilometer control area in Huanggu district, involving more than 105,000 people in 11 communities, Wang Hao, an official from the city government said at a Saturday press conference.

While businesses that provide daily necessities remain open, other public venues in the area are closed and schools and kindergartens were asked to suspend classes. 

Through epidemiological investigation, Dalian's local government revealed on Sunday, the source of the outbreak is five dock workers who were infected after handling coronavirus contaminated bulk goods on a Russian freighter. 

"Novel coronavirus can survive in a cold region for a long time, thus making the northern Chinese cities COVID-19 epidemic prone areas in winter," Yang Zhanqiu, deputy director of the pathogen biology department at Wuhan University told the Global Times.

Yang noted that given the individual imported cases emerging from time to time,and mutated coronavirus spread worldwide, departments should more strictly enforce detection and monitoring measures, focusing on strengthening management of ports, international logistics and cold chain, and vaccinating workers in relevant industries as soon as possible.