There are many theories about the source of the global COVIDs pandemic, including the idea the virus may have jumped from bats to humans at markets in China.
Not so fast, said Vikram Misra, a bat expert and microbiologist at the University of Saskatchewan.
“There’s no direct evidence,” Misra said. “The exact viruses, the very viruses that cause disease in people and other animals, those have not been found in bats.”
A delicate balance
There are, however, some important lessons to be learned about bats, according to Misra: how they deal with viruses, potentially spread them to humans and how to best prevent that from happening.
“[Bats] have lots of viruses but there are very very few viral diseases that actually make them sick,” said Misra. “They also seem to have for some of these viruses a very balanced relationship…they don’t get rid of the viruses, the viruses just sort of come along or multiply at a very very low rate.”
You know we shouldn’t blame bats for these diseases.– Vikram Misra
The problem for bats is that when they are under stress, that delicate balance tips.
“While this wonderfully balanced relationship exists between bats and some of their viruses,” Misra said, “If you stress the bats then that relationship changes and then the viruses start to multiply at a much higher rate.”
According to Misra, the risk of passing disease from bats to the human population increases when the viruses begin multiplying.
“You know we shouldn’t blame bats for these diseases, but if you want to sort of prevent spillovers of viruses from bats to other species and finally to humans we have to sort of treat them better.”
There are several factors that can lead to higher levels of stress in bats, including fungal disease, having to fly long distances for food and being confined in cages, a situation that may sometimes be seen in wet markets in China where bats are sold as food for human consumption.
How bats might help
There is one other compelling lesson that may prove useful to researchers trying to find new ways to treat COVID-19, but Misra offered an important disclaimer first.
“We don’t work with COVID-19, we work with other coronaviruses. Also all our work is in the laboratory, and so you’ve got to be a bit cautious about extending that to the real world.”
Misra suggested that when people get sick from COVID-19, the real problem that leads to severe symptoms and sometimes death is the way our bodies respond to the infection. For example, he said, inflammation can be a real problem.
Bats are different, Misra said. When they become infected, their cells turn on antiviral responses and turn off inflammatory responses, the opposite of what seems to happen in humans. Misra said there are some clues about how bats do this. It’s possible, he said, that drugs could be developed to switch on a similar response in humans.