Animals and the origins of the new coronavirus

A Facebook post claims that Dr Gauden Galea, a World Health Organisation (WHO) representative, has said that “as long as people eat meat, there is going to be some risk of infection”. 

It is true that Dr Galea, the WHO representative in China, said this.

A CNN news story (originally aired on 20 January 2020) about the role of wild animals in the new coronavirus outbreak includes a short clip of Dr Galea. In the video, Dr Galea also says: “Now with the interface with the animal world there will always be the danger of spillover.”

We can't be sure entirely what Dr Galea meant by this (we have contacted the WHO for more information). But his quotes make clear that he was referring specifically to the threat of “zoonotic” diseases—those that spread from animals to humans in “spillover” events. This doesn't necessarily mean that these diseases spread directly via people eating meat, but rather that a number of contributory factors that may raise the overall risk of zoonoses, from agricultural practises to animal markets, can be tied to the consumption of meat.

Zoonotic diseases represent a major and growing public health threat. The majority of new infectious diseases in humans are zoonotic, and this is the case for the new coronavirus. 

The new coronavirus came from an animal source

Chinese authorities linked the first reported human cases of the new coronavirus to a “wet market” in Wuhan. The market reportedly sold many species of live animals. This has led to suggestions that the source of the virus was an animal sold at the market, although this is yet to be officially confirmed.

Researchers have agreed, however, that the new coronavirus came from an animal (zoonotic) source. Bats are the most likely source—evidenced by the genetic resemblance between the new coronavirus and two bat-derived coronaviruses. Coronaviruses are a family of viruses that can infect humans and animals. Other human coronaviruses include the common cold, SARS (the severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome).

However, as explained by researchers in China, bats are unlikely to have directly passed the virus on to humans. The bat coronaviruses and the new human coronavirus that causes Covid-19 have a level of genetic distinctness that suggests that the virus passed through an intermediate animal. There is also no evidence of bats being sold in the Wuhan wet market and the outbreak occurred during hibernation for local bat species. 

Both SARS and MERS were thought to have spread to humans from bats via an intermediate animal source (civets and camels respectively), and this is likely the case for the new coronavirus too. The pangolin has been suggested as the intermediate source for the new coronavirus, although this is far from certain.

The majority of new infectious diseases in humans originated in animals

According to public health experts, zoonotic diseases, particularly those originating in wild animals, represent a major and growing health threat to humans. A study of emerging human infectious disease (EID) events between 1940 and 2004 found that 60% had zoonotic origins and, of these, 72% originated in wildlife.

The study authors write “the number of EID events caused by pathogens originating in wildlife has increased significantly with time”. The richness of wildlife species was found to predict the emergence of EID events in this study. Other research found that both wildlife richness and land-use changes were associated with EID events.

Land use changes, such as agricultural encroachment, deforestation and the expansion of urban environments, are hypothesised to be “a key driver for disease emergence by perturbing ecosystems and bringing humans into close proximity with wildlife”. 

The wild animal trade also increases the potential for spillover. Contact with the body fluids of slaughtered animals, particularly in wild animal markets, presents the “ideal circumstances for new diseases to emerge” according to Professor Andrew Cunningham, Deputy Director of Science at the Zoological Society of London.

As explained by the US Centres for Disease Control and Prevention, disease can spread from animals to humans through direct contact with the body fluids of an infected animal or indirect contact, by coming into contact with areas where animals live or roam. Infections can also be passed through water and food contaminated with faeces from an infected animal. Bites from a tick or insect (known as vector-borne infections) are a further method of infection.