Photo: Li Hao/GT

Chinese experts differ on when the new outbreak in Beijing began and where exactly the virus originated. In the latest speculation, Gao Fu, director of the Chinese Center for Disease Control and Prevention (Chinese CDC), said the outbreak probably did not occur in early June or late May, but probably a month earlier. 

"A lot of asymptomatic or mild cases were detected in this outbreak and that is why the environment has such amount of virus," said Gao at a seminar in Shanghai on Tuesday, media reported. 

The novel coronavirus will lurk in some dark, humid, polluted environments, which may be unexpected. After that, it will suddenly be exposed to many people within a certain period of time, Gao said.

Gao said such speculation needs further verification.

Different from Gao, Wu Zunyou, chief epidemiologist at the Chinese CDC, told media on Monday that the COVID-19 cluster centered at Beijing Xinfadi Market may have begun as early as late May. 

Wu has said the outbreak in Xinfadi Market is similar to the epidemic in Wuhan's Huanan seafood market. The common feature of these markets is that they are cold and wet places, which are very suitable for viruses to survive.

Yang Zhanqiu, a deputy director of the pathogen biology department at Wuhan University, believes that this latest outbreak may have begun in early June. 

As the incubation period for the virus is about six days, with the longest being 14 days, the first confirmed patient was probably infected in early June. 

"The relationship between confirmed patients and asymptomatic patients is just like an iceberg. On the top of the iceberg are confirmed cases, while asymptomatic cases are at the bottom. The two kinds of patients exist at the same time and the difference is that the asymptomatic patients have not showed symptoms yet," Yang said.

Yang predicted that as the capital city has beefed up measures to curb the spread of the virus and raised the emergency response to level II on Tuesday night, the situation will be controlled within two weeks or maybe even one.

Zeng Guang, chief epidemiologist of the Chinese CDC, is also optimistic about the situation. Zeng believes that the latest COVID-19 outbreak in Beijing will soon reach its peak. He predicted that if the public continues to uphold the country's prevention and control measures, it will subside in around one month.

"Don't be alarmed by the severity of the outbreak. This virus is our old enemy, and we are very good at dealing with it," Zeng told the Global Times. 

At present, the key lies in the rapid detection and control of the outbreak in key regions in Beijing, so as to prevent the spread to other places and provinces, Zeng said. 

Pang Xinghuo, a deputy director of the Beijing Municipal Center for Disease Prevention and Control, said during Wednesday afternoon's conference that so far, the outbreak has been concentrated in the Xinfadi market. Most of the 137 confirmed cases are directly or indirectly related to the employees and shoppers of the market. They are mainly centered in the Huaxiang area of Fengtai district, where the Xinfadi market is located.

Pang said that it is possible that new infections will emerge for some time to come.