A two-member advance team of World Health Organization (WHO) experts has left for China to organise an investigation into the origins of the novel coronavirus behind a pandemic that has killed more than 550,000 people globally, the UN agency said on Friday (Jul 10).

The virus is believed to have emerged in a wholesale market in the central Chinese city of Wuhan late last year after jumping the species barrier from the animal kingdom to infect humans.

The two WHO experts, specialists in animal health and epidemiology, will work with Chinese scientists to determine the scope and itinerary of the investigation, WHO spokeswoman Margaret Harris said, declining to name them.

"We know it's very, very similar to the virus in the bat, but did it go through an intermediate species? This is a question we all need answered," Harris told a news briefing.

WHO director-general Tedros Adhanom Ghebreyesus later told a news conference: "Two WHO experts are currently en route to China to meet with fellow scientists and learn about the progress made in understanding the animal reservoir for COVID-19 and how the disease jumped between animals and humans."

He added, "This will help lay the groundwork for the WHO-led international mission into the origins."

COVID-19 is the respiratory disease caused by the virus.