Nipah. Hendra. Ebola. Marburg. SARS. These are some of the world’s scariest viruses.
Hemorrhagic fevers like Ebola are extremely fatal – they kill up to 90 percent of people
infected – while SARS, a coronavirus, has a lower mortality rate but spreads incredibly
rapidly. All of these nasty pathogens have surfaced in humans in just the last 50 years,
and they are all carried by bats.
Which, to be clear, really isn’t bats’ fault: the recent rise in outbreaks is likely
due to humans and our animals creeping ever-farther into bats’ territory, especially in the
tropics. In Malaysia, for example, the spread of commercial pig farms into bat-inhabited
forests led to the first human outbreak - via pigs - of Nipah. And in Australia, human hendra
cases are cropping up as destruction native forests forces fruit bats to feed in suburban
gardens.
But still: bats do appear to carry more human-killing diseases than pretty much any other animal.
One big reason is that, with a few notable exceptions, bats love company — different
kinds of bats often roost together in huge numbers and close quarters, which helps viruses
spread not just between individuals, but also between species .
What’s more, most infected bats don’t die — they live pretty normal bat lives,
flapping around and giving the viruses time to spread. In fact, flight may be the reason
bats are so resilient to infection.
As a rule, mammals can’t produce the immense amount of energy needed for flight without
also producing a lot of reactive waste products that damage our DNA. So when our bat cousins
took to the air, they leveled-up their in-flight DNA damage repair kits and other defenses,
including specialized cells that keep viral invaders in check.
So bats can survive the deadly viruses - but what may matter even more, for humans anyway,
is how the viruses survive the bats.
Nasty as they are, most viruses are also extremely finicky — in order to thrive, they require
the perfectly controlled climate inside a normal, resting, on-the-ground mammal. But
when bats take to the air, their internal temperatures cruise to around 40°C. Those
frequent in-flight saunas are far too toasty for your average virus, but a few hardy viruses
have evolved to tolerate the heat. Which, incidentally, means they can definitely weather
a meager human fever. Essentially, flight may have helped bats gain virtual immunity
to viruses AND trained viruses to be virtually immune to us. Stupid flying.
So, what should we land-lubbers do? We need bats for insect control and pollination - and
a whole bunch of other things - maybe we could even learn some immune tricks from them - like
how to be really good at not getting cancer! Plus, bats aren’t the biggest carriers of
human disease. Humans are - just do the math. Perhaps we’d be better off leaving bats
alone, and trying to control the spread of diseases carried by a different kind of flying
mammal.