No One Could Have Guessed Our Worst Fears at Best

It’s easy to point at someone who can’t defend themselves, or bully the classe’s fattest kid. Just like those who suffer from bullying, bats are always the scapegoat! Within some cultures they have a bad reputation with magical forces associated to them, however in China, they are good luck symbol — actually the Chinese word for bat means “good luck“. So, what do we really know about this mouse in a leather suit?   

According to a recent British study, bats have relatively no more pathogens than other mammals or birds. However, due to the COVID-19 pandemic, bats have gained a bad reputation. Rabies is the only disease known to kill bats as well.

Based on studies of bat feces found in Yunnan, China, the species from which the SARS-CoV-2 virus ended up in humans is an intermediate horseshoe bat (Rhinolophus affinis). Seven coronaviruses that have caused epidemics have been transmitted from bats to humans. The four viruses found in the last half of the century were and still are mild influenza. Of the 21st century entrants, SARS and MERS are much more deadly than COVID-19, but less contagious. Precisely because of its high infectivity, COVID-19 became a pandemic.

Dr Jefferson believes the virus may be transmitted through the sewage system or shared toilet facilities, not just through droplets expelled by talking, coughing and sneezing. Exploring why so many outbreaks happen at food factories and meat-packing plants could uncover major new transmission routes, they believe (Dr Jefferson and Professor Carl Henegehan, director of the CEBM). It may be shared toilet facilities, coupled with cool conditions, that allow the virus to thrive. “We’re doing a living review, extracting environmental conditions, the ecology of these viruses which has been grossly understudied,” said Dr Jefferson. “There is quite a lot of evidence that huge amounts of the virus were in sewage all over the place, and an increasing amount of evidence there is faecal transmission. There is a high concentration where sewage is four degrees, which is the ideal temperature for it to be stabled and presumably activated. Meat-packing plants are often at four degrees. “These meat-packing clusters and isolated outbreaks don’t fit with respiratory theory, they fit with people who haven’t washed their hands properly.

Many scientists have come to the conclusion that only a very small proportion of zoonoses are likely to be known. New diseases are easily overlooked, if symptoms are mild or vague, and especially, if people do not infect each other. They can only become an epidemic when they are transmitted from person to person. If a bat virus makes a sick person and even kills a human, how is it possible that an an intermediate horseshoe bat under 15 grams is not a scientific companion in her body? The answer form Thomas Lilley, curator of the Central Museum of Natural History (Luomu) may surprise. The reason is a skill that no other mammal has.

Flying is such a heavy burden on bats that sometimes their own cells cannot withstand it, but break down, releasing their genome outside the cells. If a person has a freely migrating genetic material, the body usually attacks it quickly and triggers various immune reactions because it considers it a potential virus or other pathogen. – If a bat does so, it would have a constant autoimmune reaction. The bat would get sick and not be able to get food or live normally anyway, Lilley explains. Therefore, the bat let it be. It has a suppressed immune response. Its body does not attack the genome drifting outside the cells, neither its own nor its foreign. The human defence system, on the other hand, uses weapons so heavy that they can also harm the person himself. – In many diseases, the host’s own reaction to the virus causes more symptoms than the actual cause of the disease, Lilley confirms.

The bat preys on two rupees at night and digests its food between them. Here flies a pick-up bat whose homeland extends from western Canada to central Mexico. Image: Rick & Nora Bowers / AOP

The microbes do not aim to make the host sick, not even killing. They only seek to benefit from the host cells in order to replicate themselves. Otherwise, the virus will not be able to multiply. If the host does not respond with a response, it will not get sick.

However, the severity of COVID-19 is not solely due to an autoimmune reaction in which a person damages their own tissues. The virus also destroys lung cells. Doesn’t the same happen to bats? – No. Their relationship is commensalistic, which does not harm the host. It is a product of very long co-evolution. The virus is so adapted to its host that it can live and reproduce in it without causing any inconvenience, says Thomas Lilley.

An air-squeezing bat has an inherently high temperature. “Viruses are used to flying bats raising the temperature to 40 or even 42 degrees every night. Viruses don’t break it down, Lilley explains. The commensalism of the bat and its viruses has developed over a very long period of time. It would not threaten humanity if man himself had not changed the world so that he would come into more and more contact with viruses from other animals. “That’s the biggest problem here,” says Lilley.

In a place like China’s animal markets, the situation is different. When bats kept in cages become stressed, the secretion of viruses increases and they can infect a larger mammal that does not have resistance to it. – It then has such a powerful machinery and body that it starts pushing out the virus particles properly. At the same time, mutations occur that allow the virus to infect humans. It may also be sufficient for the intermediate host to come into contact with bat feces, urine or saliva. They also have the virus – the more stressed the bat, the more. The pandemic has sparked bat anger in some, and there is already outright bat persecution in China, says Thomas Lilley.

If bats were not eating insects and eating flowers, there would be immediate consequences for public health and the economy. – For example, 500 plant species would not be pollinated. Harmful insects would increase. Malaria and dengue fever would certainly affect many more people, Lilley lists.

Indeed, bats very rarely get cancer. One possible explanation was provided last year by a U.S. study that looked at the effect of environmental toxins on bat cells.

Wallius, Anniina. 2020. Yle uutiset – Lepakkojen virus aiheutti ihmisille pandemian mutta lepakot eivät sairastu – evoluutio on hyvittänyt kömpelö’ä lentäjää erikoisella immuunijärjestelmällä. 16. 04.
Consulted on 7.7.2020

Every species have their own specific place and purpose in the ecosystem and we should respect the nature and diversity of our planet.   

Did you know that there is a total of 1,200 species of bats in the world? The wingspan of the largest bats is one and a half meters, the smallest only 15 centimeters.

The views and opinions expressed in Bertin Environics Blog are those of the authors and do not necessarily reflect the official policy or position of Environics Oy. Any content provided by the authors are of their opinion and are not intended to malign any religion, ethnic group, club, organization, company, individual, neither they serve as a scientific statement.


Toni Leikas

Training Manager

I am Toni, a CBRN professional with over 20-year experience in training and educating Security and CBRN matters. I have trained operators from over 50 different nationalities, from a wide range of occupational areas from First Responders to Scientists.

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