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  • The story that I'm going to tell you today,

  • for me, began back in 2006.

  • That was when I first heard about an outbreak of mysterious illness

  • that was happening in the Amazon rainforest of Peru.

  • The people that were getting sick from this illness,

  • they had horrifying symptoms, nightmarish.

  • They had unbelievable headaches,

  • they couldn't eat or drink.

  • Some of them were even hallucinating --

  • confused and aggressive.

  • The most tragic part of all

  • was that many of the victims were children.

  • And of all of those that got sick,

  • none survived.

  • It turned out that what was killing people was a virus,

  • but it wasn't Ebola, it wasn't Zika,

  • it wasn't even some new virus never before seen by science.

  • These people were dying of an ancient killer,

  • one that we've known about for centuries.

  • They were dying of rabies.

  • And what all of them had in common was that as they slept,

  • they'd all been bitten by the only mammal that lives exclusively on a diet of blood:

  • the vampire bat.

  • These sorts of outbreaks that jump from bats into people,

  • they've become more and more common in the last couple of decades.

  • In 2003, it was SARS.

  • It showed up in Chinese animal markets and spread globally.

  • That virus, like the one from Peru, was eventually traced back to bats,

  • which have probably harbored it, undetected, for centuries.

  • Then, 10 years later, we see Ebola showing up in West Africa,

  • and that surprised just about everybody

  • because, according to the science at the time,

  • Ebola wasn't really supposed to be in West Africa.

  • That ended up causing the largest and most widespread Ebola outbreak

  • in history.

  • So there's a disturbing trend here, right?

  • Deadly viruses are appearing in places where we can't really expect them,

  • and as a global health community,

  • we're caught on our heels.

  • We're constantly chasing after the next viral emergency

  • in this perpetual cycle,

  • always trying to extinguish epidemics after they've already started.

  • So with new diseases appearing every year,

  • now is really the time

  • that we need to start thinking about what we can do about it.

  • If we just wait for the next Ebola to happen,

  • we might not be so lucky next time.

  • We might face a different virus,

  • one that's more deadly,

  • one that spreads better among people,

  • or maybe one that just completely outwits our vaccines,

  • leaving us defenseless.

  • So can we anticipate pandemics?

  • Can we stop them?

  • Those are really hard questions to answer,

  • and the reason is that the pandemics --

  • the ones that spread globally,

  • the ones that we really want to anticipate --

  • they're actually really rare events.

  • And for us as a species that is a good thing --

  • that's why we're all here.

  • But from a scientific standpoint, it's a little bit of a problem.

  • That's because if something happens just once or twice,

  • that's really not enough to find any patterns.

  • Patterns that could tell us when or where the next pandemic might strike.

  • So what do we do?

  • Well, I think one of the solutions we may have is to study some viruses

  • that routinely jump from wild animals into people,

  • or into our pets, or our livestock,

  • even if they're not the same viruses

  • that we think are going to cause pandemics.

  • If we can use those everyday killer viruses

  • to work out some of the patterns

  • of what drives that initial, crucial jump from one species to the next,

  • and, potentially, how we might stop it,

  • then we're going to end up better prepared

  • for those viruses that jump between species more rarely

  • but pose a greater threat of pandemics.

  • Now, rabies, as terrible as it is,

  • turns out to be a pretty nice virus in this case.

  • You see, rabies is a scary, deadly virus.

  • It has 100 percent fatality.

  • That means if you get infected with rabies and you don't get treated early,

  • there's nothing that can be done.

  • There is no cure.

  • You will die.

  • And rabies is not just a problem of the past either.

  • Even today, rabies still kills 50 to 60,000 people every year.

  • Just put that number in some perspective.

  • Imagine the whole West African Ebola outbreak --

  • about two-and-a-half years;

  • you condense all the people that died in that outbreak

  • into just a single year.

  • That's pretty bad.

  • But then, you multiply it by four,

  • and that's what happens with rabies every single year.

  • So what sets rabies apart from a virus like Ebola

  • is that when people get it,

  • they tend not to spread it onward.

  • That means that every single time a person gets rabies,

  • it's because they were bitten by a rabid animal,

  • and usually, that's a dog or a bat.

  • But it also means that those jumps between species,

  • which are so important to understand, but so rare for most viruses,

  • for rabies, they're actually happening by the thousands.

  • So in a way, rabies is almost like the fruit fly

  • or the lab mouse of deadly viruses.

  • This is a virus that we can use and study to find patterns

  • and potentially test out new solutions.

  • And so, when I first heard about that outbreak of rabies

  • in the Peruvian Amazon,

  • it struck me as something potentially powerful

  • because this was a virus that was jumping from bats into other animals

  • often enough that we might be able to anticipate it ...

  • Maybe even stop it.

  • So as a first-year graduate student

  • with a vague memory of my high school Spanish class,

  • I jumped onto a plane and flew off to Peru,

  • looking for vampire bats.

  • And the first couple of years of this project were really tough.

  • I had no shortage of ambitious plans to rid Latin America of rabies,

  • but at the same time,

  • there seemed to be an equally endless supply of mudslides and flat tires,

  • power outages, stomach bugs all stopping me.

  • But that was kind of par for the course,

  • working in South America,

  • and to me, it was part of the adventure.

  • But what kept me going

  • was the knowledge that for the first time,

  • the work that I was doing might actually have some real impact

  • on people's lives in the short term.

  • And that struck me the most

  • when we actually went out to the Amazon

  • and were trying to catch vampire bats.

  • You see, all we had to do was show up at a village and ask around.

  • "Who's been getting bitten by a bat lately?"

  • And people raised their hands,

  • because in these communities,

  • getting bitten by a bat is an everyday occurrence,

  • happens every day.

  • And so all we had to do was go to the right house,

  • open up a net

  • and show up at night,

  • and wait until the bats tried to fly in and feed on human blood.

  • So to me, seeing a child with a bite wound on his head or blood stains on his sheets,

  • that was more than enough motivation

  • to get past whatever logistical or physical headache

  • I happened to be feeling on that day.

  • Since we were working all night long, though,

  • I had plenty of time to think about how I might actually solve this problem,

  • and it stood out to me that there were two burning questions.

  • The first was that we know that people are bitten all the time,

  • but rabies outbreaks aren't happening all the time --

  • every couple of years, maybe even every decade,

  • you get a rabies outbreak.

  • So if we could somehow anticipate when and where the next outbreak would be,

  • that would be a real opportunity,

  • meaning we could vaccinate people ahead of time,

  • before anybody starts dying.

  • But the other side of that coin

  • is that vaccination is really just a Band-Aid.

  • It's kind of a strategy of damage control.

  • Of course it's lifesaving and important and we have to do it,

  • but at the end of the day,

  • no matter how many cows, how many people we vaccinate,

  • we're still going to have exactly the same amount of rabies up there in the bats.

  • The actual risk of getting bitten hasn't changed at all.

  • So my second question was this:

  • Could we somehow cut the virus off at its source?

  • If we could somehow reduce the amount of rabies in the bats themselves,

  • then that would be a real game changer.

  • We'd been talking about shifting

  • from a strategy of damage control to one based on prevention.

  • So, how do we begin to do that?

  • Well, the first thing we needed to understand

  • was how this virus actually works in its natural host --

  • in the bats.

  • And that is a tall order for any infectious disease,

  • particularly one in a reclusive species like bats,

  • but we had to start somewhere.

  • So the way we started was looking at some historical data.

  • When and where had these outbreaks happened in the past?

  • And it became clear that rabies was a virus

  • that just had to be on the move.

  • It couldn't sit still.

  • The virus might circulate in one area for a year, maybe two,

  • but unless it found a new group of bats to infect somewhere else,

  • it was pretty much bound to go extinct.

  • So with that, we solved one key part of the rabies transmission challenge.

  • We knew we were dealing with a virus on the move,

  • but we still couldn't say where it was going.

  • Essentially, what I wanted was more of a Google Maps-style prediction,

  • which is, "What's the destination of the virus?

  • What's the route it's going to take to get there?

  • How fast will it move?"

  • To do that, I turned to the genomes of rabies.

  • You see, rabies, like many other viruses, has a tiny little genome,

  • but one that evolves really, really quickly.

  • So quickly that by the time the virus has moved from one point to the next,

  • it's going to have picked up a couple of new mutations.

  • And so all we have to do is kind of connect the dots

  • across an evolutionary tree,

  • and that's going to tell us where the virus has been in the past

  • and how it spread across the landscape.

  • So, I went out and I collected cow brains,

  • because that's where you get rabies viruses.

  • And from genome sequences that we got from the viruses in those cow brains,

  • I was able to work out

  • that this is a virus that spreads between 10 and 20 miles each year.

  • OK, so that means we do now have the speed limit of the virus,

  • but still missing that other key part of where is it going in the first place.

  • For that, I needed to think a little bit more like a bat,

  • because rabies is a virus --

  • it doesn't move by itself,

  • it has to be moved around by its bat host,

  • so I needed to think about how far to fly and how often to fly.

  • My imagination didn't get me all that far with this

  • and neither did little digital trackers that we first tried putting on bats.

  • We just couldn't get the information we needed.

  • So instead, we turned to the mating patterns of bats.

  • We could look at certain parts of the bat genome,

  • and they were telling us that some groups of bats were mating with each other

  • and others were more isolated.

  • And the virus was basically following the trail laid out by the bat genomes.

  • Yet one of those trails stood out as being a little bit surprising --

  • hard to believe.

  • That was one that seemed to cross straight over the Peruvian Andes,

  • crossing from the Amazon to the Pacific coast,

  • and that was kind of hard to believe,

  • as I said,

  • because the Andes are really tall -- about 22,000 feet,

  • and that's way too high for a vampire to fly.

  • Yet --

  • (Laughter)

  • when we looked more closely,

  • we saw, in the northern part of Peru,

  • a network of valley systems that was not quite too tall

  • for the bats on either side to be mating with each other.

  • And we looked a little bit more closely --

  • sure enough, there's rabies spreading through those valleys,

  • just about 10 miles each year.

  • Basically, exactly as our evolutionary models had predicated it would be.

  • What I didn't tell you

  • is that that's actually kind of an important thing

  • because rabies had never been seen before on the western slopes of the Andes,

  • or on the whole Pacific coast of South America,

  • so we were actually witnessing, in real time, a historical first invasion

  • into a pretty big part of South America,

  • which raises the key question: