Three things we learned from the WHO's probe into origins of COVID

Watch: COVID-19: WHO experts leave China with three theories about the origins

The World Health Organization (WHO) has unveiled the first results from its investigation into how the pandemic began.

Experts appointed by the WHO have been investigating the origins of Sars-Cov-2 – the virus that causes COVID-19 – over the last few weeks.

The team have visited sites in the Chinese city of Wuhan, where the virus first emerged in late 2019.

Since it was first detected, there have been more than 100 million cases around the globe and 2.3 million deaths.

Read: Reducing COVID to 'the sniffles' would be job done, says expert

In a press conference on Tuesday, Peter Ben Embarek, head of the WHO mission and Liang Wannian, the lead Chinese envoy, spoke about their findings during phase one of the probe.

Embarek said: “We came here with two goals. One was to try and get a better understanding of what happened at the beginning of the event in December 2019. In parallel, we also embarked on trying to understand ... how did the virus emerge."

While the WHO team have so far given no solid answers on exactly how the pandemic began, here are three things that we have learned from their announcement.

‘Extremely unlikely’ virus came from lab

China has faced claims that the Wuhan Institute of Virology could be the suspected source of the Covid-19 virus.

But the controversial theory, which was peddled by former US president Donald Trump, is “extremely unlikely”, the investigators found.

Embarek told the press conference: “The laboratory incident hypothesis is extremely unlikely to explain the introduction of the virus into the human population. Therefore [it] is not in the hypotheses that we will suggest for future studies."

When asked about the possibility of a lab incident, he said: "Nowhere previously was this particular virus researched, or identified, or known.

"There had been no publication, no reports of this virus or another virus extremely closely linked to this being worked with in any other laboratory in the world."

Embarek said that investigators examined staff monitoring programmes and audits in research labs, adding: "We looked for examples at the Wuhan Institute for Virology and the state of that laboratory and it was very unlikely that anything could escape from such a place."

Liang added that none of the labs in Wuhan had worked with Sars-Cov-2 — only on the virus’s distant relatives.

He said that it is possible the virus jumped across species through intermediary hosts such as pangolins, cats or minks.

Embarek agreed, saying: "Our initial findings suggest that the introduction through an intermediary host is the most likely pathway and one that we will require more studies and more specific targeted research."

Peter Daszak, a British member of the WHO mission, wrote on Twitter that the judgement on the lab theory was unanimous among the team’s 17 members.

COVID may not have originated in Wuhan wet market

The Huanan Seafood Market in Wuhan has been identified as somewhere the virus first started spreading among humans in December 2019.

However, the WHO team said that the virus was spreading both inside and outside the market in Wuhan at the same time, which could indicate that it was not the original source of the outbreak.

They added that they "don't know" the exact role of Wuhan's Huanan Seafood Wholesale Market in the origin of the virus.

A cluster of cases was linked to the market, but officials also found cases among people who had no ties to the market.

Watch: 'Striking piece of evidence': WHO researcher on products in Wuhan market

Some had links to other markets and others had no links to markets at all, they said.

Liang said: "Huanan market may not be the first place that had the outbreak and it is not the place that witnessed the earliest case either.

"The onset date of the earliest case in this joint research was December 8 2019. The earliest case which has an association with Huanan seafood market was December 12.”

Embarek added: "We don't know the exact role of the Huanan market, we know there was spread among people who work and live and visited the market throughout December. How it was introduced and spread within the market is still unknown."

He added: "The market probably was a setting where that kind of spread-out happens easily but it is not the whole story - there was also spread among individuals who were not linked to this market, they were linked to other markets, no markets, so the picture is not clear in that respect."

Liang also suggested that Sars-CoV-2 may have originated from zoonotic transmission but the location of the reservoir hosts remains to be identified.

He said that studies examining other animals as "potential reservoirs" are "massively under sampled" and the research is not adequate.

Virus could have been transmitted through cold chain food packaging

Liang and Embarek said the virus could have been transmitted through cold chain food packaging.

This is a theory that the Chinese government and its state media have reportedly been pushing recently as part of an argument that the virus may not have originated in the country.

Embarek said: “We know the virus can survive in conditions that are found in these cold, frozen environments, but we don’t really understand if the virus can transmit to humans.”

Liang added: "Sars-Cov-2 can persist in conditions found in frozen food packaging and cold chain products.

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"Cases in recent outbreaks in China have been linked to the cold chian. Studies have show that the virus can survive for a long time not onlyat low temperatures but also at refridgerated temperatures, indicating that it can be carried long distance on cold chain products."

According to the Washington Post, Liang and an official from China’s National Health Commission declared the China leg of the origins complete.

They then called for the investigation to be expanded globally, saying other countries like Italy, have now reported the discovery COVID cases weeks before they were first found in Wuhan in December 2019.

Liang said the team found no evidence that COVID-19 was spreading quietly in the city before December.

Watch: COVID-19: US intelligence claims Wuhan lab researchers had coronavirus symptoms before outbreak