The World Health Organization (WHO) has had assurances from China that an international field trip to investigate the origins of the new coronavirus will be arranged as soon as possible, its top emergency expert said on Monday. 

Chinese researchers are carrying out epidemiological studies into early cases and conditions at a seafood market in the central Chinese city of Wuhan, where the virus was first identified in the country. 

An international team of experts has been formed to carry out phase 2 studies. 

"We fully expect that we will have a team on the ground. We need to be able to have the international team join our Chinese colleagues and go to the ground and look at the results and outcomes of those phase 1 studies and verify these data on the ground," WHO emergency expert Dr Mike Ryan told a news briefing. 

This would help to ensure "that the international community can be reassured of the quality of the science," he said. 

The Wuhan market is "likely to have been a point of amplification" of virus transmission, but whether that was by human, animal or environmental spread is not yet known, Ryan said, adding that there had been human cases that preceded that event. 

According to Ryan, there may be more than one cases of patient zero in some situations, because there may be more than one species breach. 

We're increasingly seeing that viruses have been identified in many different countries, he said. 

A recent study from the Italy's National Cancer Institute suggested COVID-19 was circulating in the Italian city of Milan since September 2019, three months before it was first reported in China. 

The WHO said it was reviewing the results from Italy and seeking clarification. They would contact the paper's authors "to discuss and arrange for further analyses of available samples and verification of the neutralization results." 

"Those academic studies should be part of seeking virus origins. If we could combine the efforts of scientists across these countries and call on them to participate in the scientific investigation, we might be much closer to the truth on the virus' origin," Wang Guangfa, a respiratory expert at Peking University First Hospital, who had been to Wuhan in the early stage of the outbreak, told the Global Times on Tuesday. 

Wang added the WHO-led origin tracing should be done in any country being stricken by the pandemic, including Italy, Spain, other European nations and the U.S. 

Finding where the virus originated from is not political, but a scientific matter. Inviting international experts to China shows China's consistent open altitude in seeking the virus origin, he stressed. 

WHO director-general Tedros Adhanom Ghebreyesus and other senior officials briefed WHO's 194 member states last week on progress in the probe, mandated by health ministers last May.