Name: How bats carry deadly diseases without dying
Uploaded: 2026-03-01T10:28:24.000Z
Duration: 7 min 49 s
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I think they're these like fluffy flying mammals with a lot to offer, like tequila.

The trouble is, when bats hit the media, it's almost always over some deadly disease like Ebola or COVID 19 and even the recent Nipah virus outbreaks in India.

And yet we're not finding caves full of bats that died from coronavirus or Ebola.

Because bats don't just host deadly diseases, they seem to tolerate them really well.

Researchers think it's because they evolved with a unique ability.

So there's a number of unique features of bat immune systems and their physiology that we think have co evolved with the evolution of flight.

Flying requires an incredible amount of energy.

A bat in flight elevates its basal metabolic rate up to 15 fold.

And to put that in context, a human at full speed running is only doubling their metabolic rate.

And a rodent perhaps elevating it sevenfold.

So this is more than twice the energetic expenditure of any form of terrestrial locomotion.

Their heart rates can skyrocket to over a thousand beats per minute.

That's around four or five times more than their resting heart rate.

It's honestly remarkable that when a bat takes flight, it doesn't just like drop dead.

So a bat in flight will elevate its body temperature up to 44 degrees centigrade.

And 45 degrees centigrade is kind of the lethal limit of what mammals can tolerate.

So when in flight, they're really pushing the sort of physiological limits of thermal tolerance.

And while all of this is fascinating, you're probably wondering, okay, what does this have to do with viruses?

Well, stick with me because we are getting there.

So flight is essentially a huge stressor that resembles aging.

And because it's a part of bats innate physiology, they've evolved unique molecular pathways to mitigate that damage at the site of production.

So essentially, bat physiology is resilient to the process of aging.

You see, despite burning a ton of energy all of the time, bats are shockingly long lived.

Usually there are trade offs between metabolic output and lifespan, and rodents are a great example of that.

Typically, they only live up to a couple of years.

Bats, however, are about the same size and have metabolic expenditure that even exceeds that of rodents.

The oldest known bat lives up to 40 years in the wild.

So after actually correcting for body size, bats are the longest lived mammals on Earth.

So these special pathways that they've developed in order to mitigate the intense effects of flying have likely made them extremely tolerant to viruses, or at least primed them to successfully fight them off.

When a virus enters a human, two things happen.

Okay, more than two things happen, but let's focus on two, because who has the time?

Think of these like two switches that need to be turned on when a virus infects a cell, and

So when a virus shows up, it enters a cell and your body raises an alarm, like, hey, there's a guy here who's not even supposed to be here, that flips the alarm switch, which releases some molecules that slow the virus from replicating.

And then the second switch flips, which launches an immune response to kill off the rest of the virus.

Once that immune response switches on, our bodies can sometimes start to experience some pretty severe symptoms, like a fever, body aches, and

essentially inflammation, which sure fights the virus.

But also the immune response causes widespread inflammation in the body, which is, and of itself, highly fatal.

But bats can't have their body triggering inflammation every time they experience an extreme stressor, because their entire existence as a flying mammal is basically an extreme stressor.

And so their switch responses to an invader work a bit differently than ours.

So in some species, their alarm switch is perpetually on.

In other species, it's entirely in overdrive, which means they're sounding an alarm and releasing molecules to stop a virus from replicating before it even enters their body.

And their switch that triggers inflammation kind of has a permanent dimmer so they don't feel these strong side effects.

Bats are particularly adept at reducing viral loads to very low levels and simply tolerating whatever is remaining.

Which might be part of the reason why the viruses they do host are so much more dangerous to humans.

The longer a virus stays in a host, the more chances it has to replicate, mutate, jump to a new bat or animal, and

But before you start thinking about bats as these, like, horrible, disease ridden flying creeps, it's worth noting there is a lot we can learn from them, including how to better treat disease in humans.

At least one group of researchers in Dublin recently received a grant to study just that.

And some of our methods already work to mimic the switches in a bat, including how we treat many severe Covid cases.

We first treat patients with Remdesivir, which is an antiviral drug that tries to reduce the viral load.

But then later, later on in infections, we'll treat with dexamethasone, which is a steroid that's meant to actually blunt that immunopathology.

So it's anti inflammatory and so we turn the alarm on and we dim the other switch.

recent studies have shown that bats under extreme stress caused by things like rising global temperatures, habitat loss and human interference are more likely to shed and spread spread viruses.

So I feel strongly that there is a win win argument for bat conservation and human public health because a healthy bat is simply less of a zoonotic threat to humans than is a sick bat.

While bats do pose zoonotic risk, they also offer a really valuable research source for new approaches in medicine.

I'm Kim, the producer of this episode, and

there is just so much, so much we did not get to cover in this including how a broad diversity of species of bats might also contribute to why diseases they carry are so deadly, or even just the things that do affect bats, like white nose fungus.

There's a long list of topics to explore and this piece is really just meant to be a primer, but

hopefully it makes you want to learn more.

I've included a bunch of links in the description to help you get started.

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