The COVID-19 outbreak in Beijing is controllable, thanks to the quick and decisive measures taken by health authorities after infection clusters emerged in local schools this week, a senior official said at a news conference on Wednesday.

Beijing reported five cases of COVID-19 and two asymptomatic carriers between midnight and 3 pm on Wednesday. All of the cases are linked to infections at two schools, said Liu Xiaofeng, deputy director of the Beijing Center for Disease Prevention and Control.

Beijing University of Chemical Technology, which reported its first infections on Monday, has seen 18 cases in its cluster. Thirteen of them were reported on Tuesday and five on Wednesday, all from the school's campus in Changping district, Liu said.

"The number of daily cases has dropped, thanks to timely and decisive measures," he said.

Four buildings on the campus were designated as high-risk areas, Bai Lin, deputy head of Changping district, said at the same news conference.

More than 1,100 people identified as close contacts and sub-close contacts of those infected were placed in quarantine or under a different health management protocol, Bai said. Some 100 medical workers were deployed to help the school conduct mass nucleic acid testing.

For three straight days starting on Tuesday, nucleic testing will be carried out in the places visited by those who tested positive for the virus. So far, all the tests have come back negative, Bai said.

The other cluster of infections emerged on Tuesday at the High School Affiliated with Minzu University of China.

By 3 pm on Wednesday, the school reported three cases of the virus. One was on Tuesday and two were on Wednesday, according to Xu Zhentao, deputy head of Haidian district, where one of the school's campuses is located.

The three infected patients are classmates who live in the school's dormitories. Two of them recently returned to Beijing from other provinces.

"They hadn't been out of the school since the new semester started on Sept 1," Xu said.

To cut off transmissions, 991 people from the school who are close contacts or at high risk of being infected were placed under quarantine, Xu said.

More than 200 other nonresident students were told to stay at home, and other students and staff members of the school will be under isolation management and be given tests for three consecutive days, Xu added.

Another infection cluster hit Jilin province in Northeast China. As of Tuesday, Changchun in Jilin province had reported 18 confirmed cases and 195 asymptomatic cases, all of which are linked to a local hospital, according to the Changchun health commission.

The first five cases were found in the city's hospital for infectious diseases on Aug 31.

Seven officials from the city were punished for failing to prevent and control the outbreak, according to a statement from the provincial disciplinary watchdog on Tuesday.

The officials, including a vice-mayor of Changchun and the director of the Changchun health commission, were removed from their posts or given warnings.

"Relevant departments should strengthen their supervision for hospital infection prevention and control," Jiang Rongmeng, a senior expert in infectious diseases at Beijing Ditan Hospital, was quoted as saying in a media report. "It is also necessary to increase the allocation of professional staff and promote more professional training."

He suggested that hospitals increase investment in better environmental and ventilation equipment to meet the demand for disease prevention and control.