Dongchang district in Tonghua city, Jilin province, and Wangkui county in Suihua city, Heilongjiang province, have been adjusted to high-risk areas for COVID-19 from medium-risk areas starting from Wednesday, according to local governments.

Jilin reported 46 new locally transmitted confirmed cases of COVID-19 and seven asymptomatic carriers on Tuesday, the provincial health commission said on Wednesday.

"The province had reported 133 confirmed and 57 asymptomatic cases as local transmission followed the first asymptomatic carriers returning from neighboring Heilongjiang province," said Zhang Yan, deputy director of the commission. "Of all the cases, 94 confirmed and 46 asymptomatic cases were found in Tonghua."

"The recent outbreak has the feature of a cluster infection involving 144 patients that were in some way connected to one case," said Zhang, adding that more than 60 percent of them are seniors over 60 years old and the oldest one is 92.

"The high proportion of seniors has brought great difficulties to the epidemic prevention and control work as well as medical treatments," she said. "However, the spread of the epidemic has been contained due to a series of measures, including epidemiological investigations, screening and control of those involved in the epidemic and conducting nucleic acid testing."

Tonghua has begun the second round of mass nucleic acid testing on Wednesday.

Neighboring Heilongjiang province reported 16 new confirmed cases and 31 asymptomatic carriers on Tuesday, its health commission said on Wednesday.

All confirmed cases and 20 asymptomatic carriers were detected in Wangkui, where the first asymptomatic carrier associated with the recent outbreak was reported on Jan 10.

Among the 31 asymptomatic cases, four were reported in Heilongjiang’s capital city Harbin.

The government of Harbin on Tuesday night released a statement for curbing an epidemic outbreak.

According to the statement, businesses including bath centers, small hotels, cinemas, internet cafes, leisure and fitness clubs, children’s entertainment facilities and educational institutions have been closed.

And all performances, competitions, forums, exhibitions and other large-scale activities were suspended, the statement said.

"As of Tuesday, all 2,569 nursing homes in the province had been put under lockdown management," Wei Feng, deputy director of Heilongjiang provincial Civil Affairs Department, said at a news conference on Wednesday. "No infectious cases were reported in the homes among all 93,100 senior residents and 16,500 staff members."