As the World Health Organization assembles international experts to study the origin of the novel coronavirus by first focusing on China, a study shows that the virus had existed in Italy months before it was first detected in China.

The study by the Milan-based National Cancer Institute, published last week in its scientific magazine Tumori Journal, shows that 11.6 percent of 959 blood samples from healthy volunteers enrolled in a lung cancer screening trial between September 2019 and March 2020 had developed novel coronavirus antibodies well before February.

Another study, conducted by scientists at the University of Siena in Italy, has supported the finding. Its paper, by 16 authors, was published in the same magazine with the title "Unexpected detection of SARS-CoV-2 antibodies in the pre-pandemic period in Italy". SARS-CoV-2 is the virus that causes COVID-19 disease.

The study showed that four cases dating to the first week of October 2019 were positive for antibodies.

"This study shows an unexpected very early circulation of SARSCoV-2 among asymptomatic individuals in Italy several months before the first patient was identified, and clarifies the onset and spread of the coronavirus disease 2019 (COVID-19) pandemic," the authors wrote.

"Finding SARS-CoV-2 antibodies in asymptomatic people before the COVID-19 outbreak in Italy may reshape the history of the pandemic."

Earlier, Italy reported its first two cases of COVID-19 on Jan 30 this year, when two tourists from China in Rome tested positive.

China informed the WHO of the outbreak in Wuhan, Hubei province, on Dec 31, 2019.

The UN health agency on Monday said it was reviewing the results from Italy and was seeking clarification, Reuters reported.

Last week, WHO Director-General Tedros Adhanom Ghebreyesus said that a group of international experts have started to work on the origin of the novel coronavirus.

"These are excellent and respected professionals. And I know they will do their work professionally," he said. "We will give them all the support they need."

When asked about the latest findings in Italy, Foreign Ministry spokesman Zhao Lijian said in Beijing on Tuesday that he has noticed the various reports about the time and location of the COVID-19 outbreak in the world.

Scientific issue

"It has again shown that tracing the origin of the virus is a complex scientific issue," he told a daily news briefing.

Zhao said scientists should conduct the study all over the world through their research and cooperation to better understand the animal host of the virus and its ways of transmission.

He expressed the view that China will continue to actively participate in the global scientific study on the origin of the virus and its transmission channels.

It was not the first time that scientists reported such findings. In early July, Oxford University scientists said that the novel coronavirus may have been lying dormant across the world until emerging under favorable environmental conditions, rather than originating in China.

Traces have been found in sewage samples from Spain, Italy and Brazil that predated its discovery in China.