Chinese renowned respiratory scientist Zhong Nanshan receives an interview with Xinhua in Guangzhou, south China's Guangdong Province, Jan. 28, 2020. Photo: Xinhua

Chinese top respiratory specialist Zhong Nanshan said Thursday although the COVID-19 first appeared in China, that does not necessarily mean it originated here. Some other experts believe that COVID-19 might have multiple birthplaces co-existing around the globe. 

Zhong made the remarks at a press conference jointly held by the Guangzhou government and Guangzhou Medical University.

"But we cannot say that virus comes from abroad. The question could be answered by tracing the source of the novel coronavirus and getting a result," Zhong said.

Analysts said Zhong's words indicate the toughness of the battle against the coronavirus, especially when the disease is spreading around the world but the source and transmission chain are still not completely clear. 

Yang Zhanqiu, deputy director of the pathogen biology department at Wuhan University, told Global Times that the novel coronavirus might have multiple birthplaces co-existing around the globe. 

Due to the differences of climates, the virus in some places burst out earlier and faster than others, Yang said, noting there are also possibilities that the coronavirus in Wuhan was from another source, through virus hosts like humans and animals. The chains of transmission are of vital importance to contain the disease. 

At early stage of the outbreak, it was widely believed that human-to-human transmission of the novel coronavirus started at the Huanan Seafood Market in Wuhan. But a study published on ChinaXiv, a Chinese open repository for scientific researchers, reveals the novel coronavirus was introduced to the seafood market from another location, and then spread rapidly from market to market.

COVID-19 patients who have never been to epidemic-stricken regions or contacted any infected people also appeared in countries and regions outside China. For example, the first such case in the US was found Thursday in  Northern California.

Some scientists suggested that COVID-19 is a natural coronavirus related to bat coronavirus. Investigations on viruses in wildlife found that pangolins may be intermediate hosts for the viruse.

Yang Zhanqiu noted that it is important to find the source and intermediate host of the virus. 

"We can cut off the source of the virus and better conduct prevention and control work when we know the route of transmission. Therefore, the early infection cases are highly valuable for research," he said.  

Yang Gonghuan, former vice director of the Chinese Center for Disease Control and Prevention, told the Global Times that knowing the source of the virus will help with vaccine and drug development. As for infectious diseases for which sources have yet to be determined, they must be treated with both hands: preventing imported infections and controlling internal transmission.

Experts said that China's moves of blocking cities and forbidding the trafficking of wildlife have helped narrow down the research into the transmission chain. 

At the press conference on Thursday, Zhong praised the timely intervention from the Chinese government and nationwide joint prevention and control efforts, which have successfully prevented a mass COVID-19 outbreak in China.

Zhong said that he will share China's experience with the European Respiratory Society (ERS) this weekend through livestreaming. More international cooperation is needed, including setting up a long-term mechanism, he said.