Few passengers wait at the Beijing Railway Station on Thursday. Since the new outbreak in the city started on June 11, virus control measures have been implemented that include community access restrictions, requiring people to take nucleic acid tests and enacting new travel curbs and rules. (ZOU HONG/CHINA DAILY)

The recent outbreak of COVID-19 cases in Beijing is under control as the city has seen a decline in confirmed cases, but the caseload will continue to grow for some time, health expert Wu Zunyou said on Thursday.

"It's positive that Beijing has controlled the epidemic. All the cases reported today were infected before June 12," said Wu, chief epidemiologist at the Chinese Center for Disease Control and Prevention.

He added that the full tally of locally transmitted cases will continue to emerge in the coming days, but the number of cases will decrease over time, since the newly added cases were just new confirmations, not new infections.

The city reported 21 new cases of COVID-19 on Wednesday, 10 cases less than the previous day. All the cases are related to Xinfadi wholesale market in Beijing's Fengtai district, according to Pang Xinghuo, deputy head of the Beijing Center for Disease Control and Prevention.

Beijing reported eight clusters of coronavirus infection as of Wednesday, all of which were closely connected with the Xinfadi market, according to Pang.

Research and sampling have been conducted at the market over the past few days, which showed that infected seafood vendors outnumbered vendors with positive results in beef, mutton and other sections. Those seafood vendors tended to show COVID-19 symptoms earlier than other workers, Wu said.

The facility with the seafood section also was found to be more contaminated by the novel coronavirus, he said, adding that in the early stages of the epidemic, cluster infections were found in a seafood market in Wuhan, Hubei province. Research being conducted is expected to provide more clues, he added.

"One possible reason is that the freezing and humid environment at the seafood section might contribute to preserving the virus. But more analysis is needed to determine how it triggered the new outbreak," he said.