Coronavirus: What Chinese research and testing has found out about the cause of Covid-19 - where animals the cause?

A research team in China has found positive coronavirus tests in the early stages of the pandemic contained genetic material from wild animals.

Chinese scientists published analysis of samples taken more than three years ago from the Huanan seafood and wildlife market, which has been the focus of several theories regarding the origin of the Covid-19 virus.

The authors note “it has been reported that a number of the early human cases had a history of contact with the Huanan Seafood Market”, but concede the origins of the virus “remain uncertain”.

From January 18, 2020, 457 samples were collected from 18 species of animals, comprising unsold contents of refrigerators and freezers, swabs from stray animals, and the contents of a fish tank. Covid-19 was detected in 73 environmental samples, such as the cages which contained wild animals, but none of the animal samples.

A nurse puts on PPE in a ward during the height of the pandemic

The Chinese research team posted an early version of their study online in February 2022, but they did not publish the full genetic information that was contained in the samples gathered from the market.

Last month another international group of researchers shared their own assessment of the market swabs, after spotting the genetic sequences had been posted on a scientific data-sharing website.

This new analysis, which has been validated by other scientists before being published in the journal Nature, includes more important detail about the content of those samples, which were collected from stalls, surfaces, cages and machinery inside the market.

However, the Chinese researchers have pointed out their discoveries fall short of definitive proof of how the outbreak started. "These environmental samples cannot prove that the animals were infected," the paper reads.

The paper also concludes it is possible the virus was brought into the market by an infected human.

Others have speculated the virus originated in a laboratory in Wuhan. While once dismissed as a conspiracy theory, on February 28 the claim resurfaced through FBI director Christopher Wray's comments which claimed the bureau believed Covid-19 "most likely" originated in a "Chinese government-controlled lab".

In response, Beijing accused Washington of "political manipulation".

Supporters of this theory point to the presence of a major biological research facility in the city. The Wuhan Institute of Virology (WIV) has been studying coronaviruses in bats for over a decade.