Flight is what makes bats different from any other mammal, and the ability to fly gives them the unique capacity to become infected with certain viruses while never becoming sick.
"Flying takes a lot of energy," said Pablo Brenes-Coto of the Museum of Science. "In the case of a bat, so much so that it kind of breaks the cells apart.
In other words, flying damages some of the bats’ own cells. Normally, cell damage in a mammal triggers an immune response that leads to inflammation.
“But because bats are flying on a regular basis, they’re breaking their cells on a regular basis,” Brenes-Coto said. “They can’t really have inflammation constant so much.”
And so, it is believed that bats naturally have slightly weaker immune systems. On the plus side, that keeps them from suffering constant inflammation. On the downside, at least from a human perspective, when bats get infected with coronavirus, they carry it.
“They don't kill the virus, they just keep the virus in check,” Brenes-Coto said.
Ecologists contend it’s not so much a problem that bats carry dangerous viruses, it’s that humans have put themselves, in some places, in unnaturally close contact with bats or in close contact with animals infected by bats. That occurs in such places as that “wet market” in Wuhan, China, the presumed origin of the latest coronavirus outbreak.
Bat conservancy international calls those markets "unsanitary places where live animals, including domestic animals and wildlife, are stressed and brought together in close proximity to each other.”
But in a live Twitter Q&A on Monday, the organization noted bats can't, at this point, be blamed for directly passing the infection on to humans.
One theory, based on DNA testing, is that coronavirus started in humans when snakes that ate infected bats were eaten by people. Keep in mind, SARS was transmitted to humans back in 2002 not directly from bats, but from bats to civets – a type of cat – to humans.
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