China provided the joint experts team for tracing the origin of COVID-19 with all data and materials available at that time and did not hide any cases, samples, test and analysis results, said Shen Hongbing, director of the Chinese Center for Disease Control and Prevention, at a news conference on Saturday.

Since the outbreak of the COVID-19 epidemic, China has been upholding a scientific attitude on tracing the origin of the virus and actively communicating and cooperating with the World Health Organization and has taken the initiative to invite the WHO to send an international experts team to China to conduct joint origin-tracing studies, said Shen.

Recently, some WHO officials and experts recklessly denied the joint studies results, which is totally against the spirit of science and is offensive to the scientists from all over the world who have participated in the early origin-tracing studies, he said.

After the first stage of joint research, China has continued to pool resources to carry out comprehensive scientific investigation and research, and shared related progress and conclusions with the international scientific community and scientists. The results of the first phase joint study were further confirmed by numerous findings, he said.

"We hope that the scientific community will follow a scientific attitude; keep scientists as the main body of the origin-tracing study; and strengthen exchanges, cooperation and information sharing ," he said, urging that certain individuals from the WHO return to a scientific and impartial position, and not become a tool for individual countries to politicize the origin of COVID-19.

Zhou Lei, a researcher of the Chinese Center for Disease Control and Prevention who participated in the joint study, said that, in Wuhan in Hubei province, Chinese scientists shared all the data and materials with the joint experts team, including the early case information and the case data of over 76,000 people who were suspected to have possibly been infected COVID-19 during the early stage in Wuhan.

"We conducted in-depth joint analysis and studies of these data and materials, and the results were collectively confirmed by the experts at that time," Zhou said.

To study the possibility of laboratory leakage, experts also carried out field investigation and research in several laboratories in Wuhan and analyzed all the health monitoring data and possible clinical data of staff of the laboratories, she said.