Does COVID-19 come from bats?
As of June 23rd, there have been more than 9 million cases and more than 475,000 deaths from COVID-19, with cases confirmed in 213 countries around the world. All of these alarming outbreaks may have one intriguing factor in common: bats.
As a researcher in traditional Chinese medicine in Shanghai, I was really interested in understanding whether or not COVID-19 really has anything to do with bats — and if so, what is the relationship. To investigate, I set out to write this blog.
So, is it actually true?
Based on the existing scientific research, there are three points that strongly suggest a link between the new coronavirus (COVID-19) outbreak and bats:
1. Previous studies have shown that some bat SARS-CoV viruses have the potential to infect humans.
Genetic information from five patients at an early stage of the outbreak was almost identical and shared almost 80% of the genetic sequence of SARS-CoV, the virus identified in bats. The International Committee on Taxonomy of Viruses has given the virus the official name, SARS-CoV-2 (Severe Acute Respiratory Syndrome CoronaVirus-2).
As mentioned by Anna McLaughlin in a recent blog, a study back in 2015 found that 3% of Chinese villagers living close to bat caves were carrying antibodies to a similar, though less contagious, version of coronavirus, similar to SARS-COV-2.
Likewise, in 2012, six miners in China contracted a pneumonia-like disease and two died, from a mine shaft infested with different bat species and bat coronaviruses. Through later testing, researchers discovered a diverse group of coronaviruses in six bat species in these cave systems.
2. All coronaviruses use their spike proteins — which are not only the sharpest weapon of the virus but also its Achilles’ heel — to gain entry into human cells, through a complex, multi-step process.
If one imagines the spike’s mushroom shape, the cap acts as a molecular key, fitting into our cells’ locks (receptors). In Covid-19, the cap binds perfectly to a receptor called the ACE-2, which can be found in various parts of the human body, including the lungs, suggesting that the CoV 2 strains use the same host receptor for cell entry as the original bat SARS-CoV.
3. Researchers at the Wuhan Institute of Virology found that the new coronavirus is 96 % genetically identical to a bat virus (BatCoV RaTG13) — which was previously detected in the bat Rhinolophus affinis originating in Yunnan in Southern China.
According to the above evidence, scientists speculate that the natural host of the new coronavirus is indeed bats.
However, the discovery of multiple lineages of pangolin coronavirus, and their similarity to SARS-CoV-2, suggest that pangolins should also be considered as possible hosts in the emergence of new coronaviruses.
In addition, other wild animals such as snakes may also carry COVID-19, but no comprehensive results have been reported so far.
This appears to follow a similar pattern to previous coronavirus outbreaks like SARS-CoV and Middle East Respiratory Syndrome (MERS-CoV) which started in bats and was passed onto both civet cats and camels, respectively.
Research indicates that while bats do carry viruses, such as the rabies virus, that can be directly transmitted to humans, this is not necessarily the case for coronavirus.
Here, coronavirus from bats does not generally directly infect people. It needs to go to the intermediate host to complete the mutation and become a virus susceptible to humans before it can enter the human cells. But the identity of the species which served as an intermediate host for the virus is still uncertain.
However, it is important to note that the virus carried by bats can also evolve within the bat population, and even during frequent contact with humans there is a risk of mutation and thus direct infection to humans — therefore, we should try to reduce most contact with bats.
Did it really jump to humans from Huanan seafood market in Wuhan?
Chinese wet markets are simply places that offer a wide range of fresh produce, as opposed to dry markets which sell non-perishable goods such as grain or household products.
Some wet markets, but not all, also sell live animals. They are referred to as “wet” because floors are often hosed down after vendors wash vegetables or clean fish.
The narrative of the origin of coronavirus infection goes something like this: in late 2019, someone at the Huanan seafood market in Wuhan, which is now an infamous “wet market”, was infected with a virus from an animal. As a result, it has since been assumed that there are bats or pangolins for sale there.
However, bat meat was never sold in the market, and in fact, bats are not a common food source in the city of Wuhan. As reported in Nature, pangolins were also not listed on the inventory of items being sold in Wuhan.
So far, there is still uncertainty about several aspects of the COVID-19 origin story that scientists are trying hard to unravel.
However, it cannot be ruled out that the Wuhan seafood market did not give wild animals the opportunity to be in touch with farm animals that are routinely used for food, nor that people were not at any point in direct contact with wild animals.
In response to the coronavirus pandemic, all wildlife trade in China, including bat meat, was banned in January 2020.
Why do people eat wildlife?
“Bats are a food source for humans in some areas. Bats are consumed in various amounts in some regions within some Asian, African, European, and Pacific Rim countries and cultures, including Vietnam, Seychelles, Indonesia, Palau, Thailand, China, and Guam”, Wikipedia writes.
While it is true that a small percentage of Chinese people have been known to eat some wild animals, it should be emphasised that this is not mainstream: in fact, an online survey by Peking University Center for Nature Society found that nearly 97% of Chinese people are against eating wild animals.
For the few people who do eat wildlife, there are probably two main reasons for this, historically.
The first reason is food demands.
Chinese society suffered from famine during 1959–61, and as a result, wildlife was used as a source of protein and fat.
As Hu Xingdou puts it in an article for the Bangkok Post, this history has left its mark on many, and grown to be “an unforgettable part of the national memory,”. Although nowadays this is no longer the far-reaching problem that it once was, “eating novel food or meat, organs or parts from rare animals or plants has become a measure of identity to some people.”
In a way, this has become a thing of nostalgia; I’ve had conversations about this and at its core, for many, eating wildlife today might be used as a way to reach for ‘childhood taste’, especially one that was seen as a ‘lifesaving taste’.
Those with memories of the famine and hunger in China are getting older and the number of these individuals is gradually decreasing. This memory will naturally disappear.
Wildlife Conservation in China by Richard B. Harris provides a great look into the impact of the famine on China and its people, if you’re interested in learning more.
The second reason is that many medicinal needs in China have traditionally come from certain wild animals.
Traditional Chinese medicine has nothing to do with taste.
Unsurprisingly, the medicinal value of wildlife is advocated because of its ‘tonic’ quality. There is a traditional Chinese medicine called Ye Ming Sha, which is derived from the dry faeces of bats and, in traditional Chinese medicine, could be used to benefit nyctalopia (also called night-blindness) and child malnutrition. However, these qualities have not been confirmed by modern medicine.
Moreover, in China but also across the world, the greater short-nosed fruit bat is hunted for medicine — not as food.
Of course, there are people eating wildlife in many different countries and you can easily find information on western websites about hunting and eating. Thus, the risk of humans getting in contact with viruses from wildlife animals is not restricted to China or other Asian countries. At present, humans know little about viruses carried by wild animals, which is a potential threat to human life and health.
We should be in awe of nature, stay away from wild animals and stop illegal wildlife trade, if we are to reduce the risk of human infection with deadly viruses in nature.
NOTE FROM THE EDITORS: Fei is a visiting researcher in psychopharmacology working in our lab at King’s College London. She is an Associate Professor from the Shanghai University of Traditional Chinese Medicine. Thanks, Fei for writing this wonderful blog for us!