A prominent Chinese respiratory disease expert, Zhong Nanshan, said at a medical symposium on Monday that between 20 and 25 percent of fever patients treated in clinics in Guangzhou, Guangdong province, were actually infected with some variant of COVID-19.

Zhong's estimate followed a report in late April by the Chinese Center for Disease Control and Prevention estimating that more than 82 percent of the country's population had been infected by the coronavirus.

Whether there are symptoms or not, if the antibody corresponding to COVID-19 in a patient increases, it means that the person's body had been previously infected with the coronavirus, Zhong said at the symposium, which focused on treatments. He urged accelerated research and development of vaccines and medicines.

Once a person is infected with COVID-19, timely drug treatment is important, as it can greatly reduce the risk of death, Zhong said, adding that many patients do not realize this.

The main COVID-19 strain currently in Guangzhou is XBB1.9.1, he said. "Therefore, the most important task in containing the spread of COVID-19 is the research and development of vaccines and medicines."

It is also necessary to develop vaccines and medicines that can cover the XBB variant, including mRNA vaccines and recombinant protein vaccines, he said. "These vaccines are mainly targeted at some special groups, including elderly people with immune deficiencies or other serious chronic and underlying diseases."

Zhong is an academician of the Chinese Academy of Engineering and winner of the Medal of the Republic, the nation's highest honor.