A medical worker collects swab samples for nucleic acid testing in Xinglong Town of Harbin, northeast China's Heilongjiang Province, Sept. 23, 2021. Photo: Xinhua

Epidemic flare-up in Northeast China's Heilongjiang Province has further fermented as COVID-19 spread to more nearby cities and counties beyond the capital city of Harbin over the weekend as the total positive COVID-19 infections rose to 40 in five days.

Public health experts said there is a need to strengthen epidemiological studies so as to cut off potential virus transmission among inter-provincial areas ahead of the upcoming National Day holidays.

Since the first case was detected on September 21, 33 out of the 34 positive cases were confined within Bayan county and one case was in the urban district of Harbin. However, the detection of six more cases on Saturday was found to have spread to Harbin's Mulan county, Songbei district and nearby Suihua city.

More than 10 people of the current group of positive cases have a travel history to Suihua, and close contacts of those that are infected had gone to weddings. All these factors have increased the uncertainty of the epidemic resurgence. 

Wang Guangfa, a respiratory expert at Peking University First Hospital, told the Global Times on Sunday that the multiple developing points of Harbin's epidemic implies that there might be loopholes in epidemiological studies which have led to potential infections not being screened out.

Screening out potential infections and cut off virus transmission are two key methods for China's precise anti-epidemic measures, Wang noted.

Data from an outbreak model by epidemiologist Huang Senzhong of Nankai University shows that the epidemic is likely to end at the end of October and will be a medium-scale outbreak, with the total infections remaining between 50-250. In the worst scenario, the outbreak scale could reach 600 cases due to some factors.

The three confirmed cases from Suihua are close contacts from Harbin, they are also from the same family. The community where they live was listed as medium-risk region for COVID-19, authorities said at a press conference on Sunday. 

In the wake of epidemic flare-ups, Harbin's Bayan county has required all its residents to stay indoors starting from Sunday, further escalating measures to cut off virus spread chains. Daily necessities will be delivered to their doorsteps. 

To screen out more potential infections among residents, a third round of nucleic acid testing has been carried out starting from Sunday.

Harbin has registered a total of six medium-risk regions for COVID-19 and one high-risk region. 

The anti-epidemic working group of the State Council have dispatched experts to epidemic-affected regions, including Mulan county, Songbei district and Suihua city. 

Ma Xiaowei, the head of the National Health Commission who is now in Heilongjiang, said the province should strive to confine the epidemic within the controlled areas prior to the National Day holidays and curb the virus spread.