>> announcer: the following is a cnn special report. bats throughout human history seem to have this image as evil, dark and dangerous. they seem to have got this bad impression in our cultures. there is definitely something odd about them. but just because they're odd doesn't mean they're bad. bats are actually quite fascinating animals. the more you get to know them, the more fascinating they are. the more social creatures you see them become. and some of them are really beautiful. but bats do carry the viruses they carry and unfortunately, right now, it is very strange, we've probably got a bat virus that's killing people.

♪ good evening. i'm anderson cooper. when covid-19 first surfaced at the end of 2019, scientists around the world wanted to know where it came from and how this deadly virus ended up in humans. although answers are not certain, it seems likely the coronavirus originated in bats. bats are diverse and ancient creatures and they've been on earth longer than we have. despite that, there is still a lot we don't know. tonight we take a look at this enigmatic animal and dig into the mystery of covid-19. in the last 20 years, some of the deadliest virus outbreaks

have come from bats. sars, marburg, ebola. so what is it about these creatures and the way they spread pathogens that can be so dangerous? >> the fact bats are carrying viruses is not in and of itself extraordinary. every animal has its normal suite of viruses and bacteria that it normally carries. people do as well. we carry viruses, bacteria, the majority are benign or beneficial, some of which cause disease. it is the fact that bats do tend to carry a higher proportion of viruses that have the ability to infect people. the question is really, why do we see some of these incredibly bad viruses coming out of bats? >> it was 7:00 p.m. on december 30th, 2019. when a package arrived at the

wuhan institute of virology. in it, medical samples from an infectious disease hospital. several patients were suffering from atypical pneumonia. doctors suspected a possible novel coronavirus. dr. xi jung-li's cell phone rang shortly thereafter. >> she got a call from her boss who said drop whatever you're doing and come back to the lab right now. >> dr. xi is known in china as the bat woman. she's one of the leading experts on bat-borne diseases. >> she is at the central of emerging diseases in wuhan. >> the biological four safety research is the highest level of containment that exists for studying pathogenic viruses. >> doctors feared the cluster of atypical pneumonia patients in wuhan might be infected with the same family of viruses that caused the outbreak of sars in 2003. severe acute respiratory syndrome.

>> more and more people were getting infected. we started to see on chinese social media in particular, the concern was growing. >> in new york, ecohealth alliance, a nonprofit organization devoted to tracking emerging diseases, began to take notice. >> we started to get our first inkling that something unusual was happening by looking to social media in china. they mentioned there was an unusual cluster of respiratory disease going on. and i remember talking to peter about the potential this might be another sars-like event. peter dar shack is the president of ecohealth alliance. he has worked closely with the wuhan institute of virology and dr. xi. their collaboration was crucial in discovering the origin of the 2003 sars outbreak. the world health organization assembled a team. including dash dar shack, xi,

and wong, considered one of the world's top emerging disease experts to find the source of the deadly outbreak. these virus hunters were pursuing a theory that bats could be the origin of sars. the team headed to the region in southern china, hunan, to try and solve the mystery of sars. xi and other researchers started exploring caves in southern china, looking for bats that could have been the origin of that first sars outbreak. >> dr. john epstein was a researcher on that expedition. >> when we go into an environment like a bat cave to catch bats, we have to protect ourselves. that includes gloves, we wear a respirator, like a mask. and we'll wear eye protection. >> we're walking into caves that could carry the next pandemic. that's a risky thing. we go in during the day to scope out where the bats are and try to work out what species are in there. then we set up nets outside and catch them when they fly out in the evening and go back in the

morning. >> we do everything we can to ensure the safety and well being of the animals and we have a basic set of samples we correct. oral swabs, fecal pellets, blood. and we take measurements. >> over the course of eight months, they sampled caves all over southern china and then took them back to the lab. >> it really took better part of eight years of consistent and persistent sampling, testing different horseshoe bat populations around, until we finally found the missing link we were looking for. >> that link was a bat virus genetically connected to sars. capable of jumping directly from bats to humans. >> that was the nail in the coffin for us in terms of this coming from bats. >> dr. xi told us bat-borne viruses will cause more

outbreaks. we need to find them before they find us. >> that original sars coronavirus in 2003 started in china. it spread to hong kong, taiwan and then the rest of the world causing 8,000 cases and 800 deaths. >> that same year, the chinese government approved the construction of the level four lab. the first in china. it opened in 2015 and is rated to study the world's deadliest viruses. >> this p-4 laboratory will mainly be used for research on highly pathogenic infectious diseases for which there are currently no medicines or vaccines. >> flash forward to the end of 2019, that's when the team in wuhan began to investigate the strange new virus. the genetic sequence of the virus was mapped fairly quickly. she compared it to a database of 500 new coronaviruses previously identified by ecohealth alliances. there was an official match,

it became sars kv 2. the virus that calls covid-19. called covid-19 because it emerged in 2019. the new coronavirus was 96.2% similar to a virus taken from a horseshoe bat in 2013. so what does that mean exactly? >> well, 96% is a different virus. so it's a bit like the difference between us and chimpanzees. what it tells us is where the virus probably came from, it means sars covid 2 probably came from bats and probably southern china. >> wuhan is 1,000 miles away from the southern sub tropical regions of hunan province, where dr. xi says the coronaviruses have the greatest risk of jumping from animals to humans. >> most of the viruses had been in southern china and wuhan is in central china. when she first found out there was a coronavirus outbreak in wuhan, she did initially wonder, is there some chance that it could have come from her lab?

>> the wuhan institute of virology is just a few miles from where many of the first cases were reported. >> dr. xi was facing this mounting pressure. that's very alarming, particularly for those who work within that lab. >> she and her colleagues immediately isolated the virus, sequenced it, tested its behavior, and she was very relieved when she discovered that it didn't come from their laboratory. this virus had never been seen anywhere in the world. >> as her team raced to find answers, the disease was spreading fast. >> when the chinese minister of health announced that community spread was rampant in wuhan, and that asymptomatic spread was occurring, that meant the disease was out of control. >> the chinese government said they traced the source of the new virus to the western edge of a seafood market in wuhan where

wild animals were being sold and slaughtered for food and medicine. >> i can't think of a better place to be a virus than a wet market. >> 16 years before the wuhan outbreak, animal traders at guangdong caught the original sars virus also in a wildlife market. >> the viruses take hold, they swap around, and then people come and breathe it in and get exposed to it. that's how viruses spill over. >> in wuhan, the initial cluster of 41 cases of severe pneumonia, about half those patients had been to that market or worked in that market or had some degree of contact with it. >> the chinese government shut down the market. early on, tried to keep information from spreading. communicating little about the early cases. >> not only was it shut down, it was also cordoned off. you had police at nearly every corner. >> months later, the chinese centers for disease control and prevention announced that

while the new virus was found in several locations in the wuhan market, all the animals they sampled tested negative. since then other theories about the possible source of the virus have emerged. >> one of the theories that circulated was that this originated from a wildlife trapper. somebody who has brought in one of these wild creatures into the market for sale. >> the only information we have from the investigation of the market was that environmental samples were collected and of about 580 samples collected, about 37 of them came back positive for sars cov-2, this virus. >> dr. epstein says the jury is still out on whether the wuhan market is ground zero for covid-19. but he agrees that wildlife markets are breeding grounds for the next disaster waiting to happen. >> why wouldn't china just shut down markets that are selling exotic species of animals? >> the population of southern china has been doing this 5,000

years. you don't just close it down overnight.

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there are actually dozens of varieties of horseshoe bats living in a number places, including the temperate and tropical regions of central europe, africa and asia. in fact there's incredible variety among bat species. they can be found all around the world and every continent except antarctica. however, the diversity and unique abilities of bats is also what makes them tough to contend with when it comes to disease. they're the only mammal capable of actually flying, so they can easily fly and spread viruses to other animals in other communities. >> some migrate thousands of miles, and hence the viruses that they carry travel along those migratory routes. >> and though some of the pathogens bats play host to can make them sick, like rabies, they have the unique ability to host and withstand some viruses without getting sick. >> understanding how bats co-exist with diseases is very critical.

they have a very unique relationship with pathogens generally. they have a unique biology and it allows them to co-exist in different ways. >> there are various theories about why that is. it might have to do with how long bats have been around. >> bats are an ancient species. they have been on planet earth a long time and that means they've had a long history of being exposed and adapting to viruses in nature. >> another theory involves their body temperatures. >> a lot of people have come up with these sort of armchair solutions. like maybe it is because they fly and when they fly, their body temperature gets higher and that's like a fever and that gives them the ability to handle viruses more than other animals would. >> he is a biologist and tv host who did his ph.d. work on bats. >> when a virus gets into a

human and a human responds by getting a fever which is effective against a lot of viruses, it doesn't work on the bats because they're used to warm temperatures. >> so if a virus is already used to a high temperature because of bats, that rising of the fever in a human may not be effective to kill off this virus. >> exactly. >> some bats have the ability to drop their body temperatures very low in the winter. so perhaps that also helps their unique immune systems. normally, the pathogens stay hidden in bats' bodies and they don't make the jump to humans. so how do humans get infected? that's what is known as zoonotic spillover when diseases cross from animals to people. sometimes thoo spillover occurs between an animal and a human, and then transmission going forward is human to human. that's called community spread.

>> perhaps the best example of that would be hiv. the transmission happened from primates to humans many years ago and now it transmits in human/human transmission. >> covid-19 is another example. but you can also have a disease that stays in a particular type of animal which then acts as a reservoir. in that case, humans are usually infected by an animal, not another person, like with rabies. >> sometimes viruses are carried by mosquitos. a mosquito might bite an animal which carries that virus and then bite a person and transmit it like flying syringes. >> no matter how a disease makes the transition from wildlife to humans, one thing is consistent. there has to be contact. >> oftentimes it is through indirect or accidental exposure. an animal that is infected may contaminate food or water people are eating and that's how they get exposed. >> with these big open markets, there is a lot of people so

there is -- it's a very conductive environment for virus cross-species transmission events. >> it is a opportunity for animals that might have never have contact with each other in the wild, being artificially being brought into a highly dense, congested and highly unhygienic situation. >> how do things spread from bats to either humans or other animals? through droppings or -- >> it probably varies from one case to another. >> typically, bats shed viruses the same way humans do. in saliva, urine and feces. if a bat is highly stressed and sick, does it shed more virus? >> absolutely. that's one of the issues with these wet markets. for bats, they have coronavirus that they've adapted to and they're totally fine. you put them in a wet market situation. they get sick, they get stressed, they succumb. just like you if you work too hard and you come down with that flu. the bats get overworked. >> sometimes with zoonotic

spillover, there can also be an intermediary animal. so bats transmit to another species and then species transmits to humans. in the case of covid-19, as of now, no one can say for sure how it ended up in people. >> all the evidence we have suggests this was a virus that originated in bats and made its way into people through a natural process. >> but at this point, the greatest risk getting covid-19 is from other humans. not bats. >> really, what matters is the way that we interact with bats. most epidemics are driven by human behavior. it doesn't matter that these viruses are happily existing in a wild animal in the middle of a forest. when people encroach on that environment, we're creating opportunity for a bat virus to get into people. dust mite droppings! eeeeeww! dead skin cells! gross! so now, i grab my swiffer sweeper and heavy-duty dusters.

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they account for approximately 20% of all the world's mammal species. how many species of bats are there? >> 1,421 is the latest count, but we add at least 20 new species every year. >> so there are still species of bats that have never been -- >> oh, yeah. >> discovered? >> absolutely. >> nancy simmons is the curator

in charge of mammology, at the museum of natural history. >> why are bats nocturnal? >> well, the thought is that actually, the ancestors of all mammals are all nocturnal. small animals scurrying around in the age of dinosaurs. it gave them access to resources that other animals like dinosaurs couldn't use. so bats basically never gave up that lifestyle. whereas the ancestors of us, primates, gave up the nocturnal lifestyle to be diurnal. >> but working at night it helps the bats how? >> if you think about what the animals are that are active in the air, during the day, it's birds. and by being active at night, bats are not competing directly with birds. so the bats basically fulfill all the same ecological roles that birds do, only they do it at night. >> bats are unique mammals. though structurally in some ways

they're similar to humans. so bats have four limbs, two of them are attached to the wings. >> two of them are the wings. >> okay. >> yes. they have all the same bones that humans do. the upper arm, the forearms, the wrist bones, and then the bones that support the end of the wing are long finger and hand bones. >> bats' living and eating habits vary widely across the 1,421 species that exist. there are some that roost in trees, others in leaves, leaves, some in caves. some bats eat insects, others, fruit or even fish and frogs. these species, some of them are living right next on each other. >> absolutely. one square mile of rain forest in for instance the brazilian amazon could have 100 species of bat.

>> the smallest bat in the world, it is this tiny thing in thailand that weighs less than a penny. the biggest bat in the world has more than a six-foot wing span. there is a bat that lives in the cloud forests of ecuador that has the longest tongue of any mammal. this thing has a tongue that is 1 1/2 times the length of its body. if you stick your arm straight out in front of and you imagine your tongue could touch your fingers, it is three times that long so it can get into a flower to pollinate. >> so relative to its body size, if i stick my arm out, if my tongue could be to the end of my arm, this bat's tongue would go two more arms? >> that's right. >> there are a number of cute bats including one dubbed the panda bat. and another, cocobo rossi,

tube-nosed bat, discovered in 2017 which made news for its resemblance to the former hairstyle of 'n sync's lance bass. >> there's the honduran white bat which looks like a cotton ball. you have your flying foxes that look like puppies but then you have some really ugly bats like wrinkle face bats. i like the ugly bats more than the cute bats. >> a bat that only a mother and dan riskin can love. >> blood feeding bats, or vampire bats do exist. but they're only about .2% of all bat species. they live in central and south america and prey on the blood of birds, pigs and cattle. >> vampire bats are super weird among bats. they sneak up on a cow. they put their face up against the cow. they have heat sensors on their nose to tell where the blood is close to the skin. they shave the area with their teeth before they cut. they lick the area to clean it,

then they make a little divot with their front teeth, and they put their jaw up against that hole and they lick and drink and pee. it is completely creepy. who else does that? >> i'll tell you who else. a serial killer does that. however, vampire bats don't kill their victims. they just act like a mammal sized parasite. i've heard you say that the weirdness of bats was scientifically interesting to you. >> the faces of bats is a perfect example of that. if you take a bat that has a weird flap on its nose, you think that's a strange looking adornment, it turns out a lot of bats have food in their mouth when they're trying to echo locate and it is hard to shout when you have food in your mouth so they hum. that weird flap actually points echo location sound where they want it to go. >> most bats navigate and hunt for food in the dark using echo location in which they emit sound from their nose and mouth and then listen for the echo

that bounces back to create a mind map of their surroundings. their often oversize ears also help. some have such sensitive hearing, they can detect the sound of an insect landing on a leaf. are bats social animals? >> it depends on the species. some spend their whole lives pretty much alone. other bats will mate for life. you have some species where there is a male and a harem of females. he gets to mate with all of them but they have their own likings in mind so they'll sometimes cheat with nearby males from other colonies. there's a whole soap opera going on with bats when it comes to mating. by the way, bat mothers are excellent mothers. imagine having a baby that weighed a quarter of what you weighed, and then the baby holds on to the mother's nipple with its teeth while she flies around. i weigh about 200 pounds. the equivalent would be if i took a 50-pound weight and put it on my nipple with a

jumper cable and just went for a run. it's incredible what these mothers do. >> that's a visual that will be with me for a while, dan. for people living with h-i-v, keep being you. and ask your doctor about biktarvy. biktarvy is a complete, one-pill, once-a-day treatment used for h-i-v in certain adults. it's not a cure, but with one small pill, biktarvy fights h-i-v to help you get to and stay undetectable. that's when the amount of virus is so low it cannot be measured by a lab test. research shows people who take h-i-v treatment every day and get to and stay undetectable can no longer transmit h-i-v through sex. serious side effects can occur, including kidney problems and kidney failure. rare, life-threatening side effects include a buildup of lactic acid and liver problems.

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in north america alone there are 46 different species of bats. most of which are small insect eating varieties like the big brown bat and the little brown bat.

but in the southeastern parts of the united states, in particular, texas, there's an abundance of one species. the mexican free tail bat. that bracken cave outside san antonio is believed to be home to the single largest colony of bats in the world. >> every year during the spring and summer, i think there are something like 30 million bats in the cave. >> in the cave? >> in the cave. in the summer. there are so many bats that the local weather stations use their doppler radar. they can see the cloud of bats coming out and spreading over the landscape to catch insects. >> really? >> it takes hours for them, there are so many commuting basically from wherever they're sleeping during the day to where their food is. >> they go the same way each time? >> yes. >> in an ecosystem, what role do bats have? >> yes. they're a really critical, key

component. for instance, insect eating bats, because they consume so many insects, they play a large role in controlling insect populations. >> a normal size bat can eat up to 500 to 1,000 mosquitos in an hour that might be carrying diseases like zika or malaria. if you're in an area where there are a lot of mosquitoes and you see bats at night, you should be thankful for those bats. >> exactly. >> and that translates into big money for agriculture. the mexican free tail bat eat huge numbers of moths, protecting the corn crops of the region. >> people have estimated the financial impact of bats on the u.s. economy is that they're worth well over $1 billion a year every single year. >> really! >> yes. in terms of how many pesticides we don't need to use. >> but pest control isn't the

only contribution to the ecosystem, they are fruit eating bats help disperse seeds and regenerate trees and plants previously cut down. and that's not the only benefit. >> bat droppings are full of nitrogen so they're good for crops and there are all kinds of stories about these caves in the united states being harvested for fertilizer and then for explosive for the civil war. >> there are also bats that serve as the only pollinators of particular types of bananas, mangos and even cacti. the muzzles of these are designed to fit perfectly in these cactus blossoms, blossoms that only open at night. >> agave which is used for tequila, that is pollinated by bats. >> exactly. who doesn't love tequila, right? just right there, that should be reason enough for people to love bats. >> despite the millions of bats in bracken cave, in north america, over the last decade and a half, bat populations have

been plummeting all because of an outbreak they've been fighting of a disease called white nose syndrome. >> it is a cold loving fungus that grows on the bat when the bats are hibernating in the wintertime. unfortunately this has affected in the order of of a dozen different species of north american bats. in some cases, populations have declined over 90%. >> that's huge. >> yes. it is a terrible let the to bats and ironically, it is a disease that we brought to bats. the fungus that causes this disease is identical to fungus that naturally occurs in europe. the thought is it was accidentally brought over by people. it was accidentally introduced into bat caves. >> so while fighting a virus that potentially came to us from bats, bats are fighting a disease that potentially came from us. in fact no north american bats are known to have covid-19. among bat researchers, there is a concern that humans will give

covid-19 to bats. >> emerging infectious diseases can go both ways. we do know that some other animals can get covid-19. for instance, the tigers at the bronx zoo. >> for now, most research involving handling of bats across the u.s. has been put on hold because humans are currently potentially the bigger threat to bats. there's a bridge. between ideas and inspiration, trauma and treatment. gained a couple of more pounds. that's good for the babies. between the moments that make us who we are, and keeping them safe, private and secure, there's webex. ♪ ♪ beautiful.

for many of us, when we think of bats, we think of one thing. rabies. the threat of that virus is often misunderstood. >> it is not very common for americans to get rabies. >> dylan george is a former white house adviser for biological threat defense. >> in any given year there's anywhere from zero to one to two people might get infected from rabies in bats or potentially from foxes or raccoons or skunks. >> rabies has actually been around 2,000 years. for most of that time, if you got it, it was a death sentence. without treatment it is 99.99% deadly. one of the big problems in europe and the u.s. used to be wild rabid dogs.

>> ancient medical experts developed a lot of odd ideas about how you would cure rabies. they used to believe that one way to stop rabies from killing you was to take a hair from the tail of the rabid dog and insert it into the bite wound, and this is the origin of the phrase "hair of the dog" which we talk about as hangover treatment. >> then along came louis pasteur, he had been working on a vaccine for years and eventually tried to try on it a young boy who had been bitten by a rabid dog. the vaccine worked. >> most of the cases in the united states do come from bats. but the risk is low. so unless you see a bat behaving very strangely, moving around during the day in a funny way, more than likely, the bat won't be a risk to an individual.

>> okay. i'm coming. i'm coming. i'm coming, guys. >> joseph de anguli spends a lot of time answering questions about rabies. because he spends every day around bats. >> there you go. oliver, oliver is more fascinated with you all. come on, are you going to take what you want? go ahead. >> they all have their favorites, of course. >> known as new jersey's batman, he became fascinated with bats as a young boy. >> my father was a nightclub and restaurant and bar owner. so i was destined to be nocturnal. and i used to very often accompany my father to work. every so often i would go outside right before sundown and i would see these animals flying around the street lights. and my father pointed them out to me and he said those are bats. >> he quickly became obsessed he passed many childhood days in

the bronx zoo ogling these feared and revered creatures. >> the stigma attached to bats was horrible and i felt like the animal that i was seeing in person was not matching the description of what people were giving me. around the world, bats are a sign of good luck, fertility, growth, everything you can think of. bats are usually the opposite of what they're considered here in america. >> as an adult, the batman became the showman as the lead singer of the '80s metal band rocks. >> it was a very different world. although it definitely paralleled the bat world. we were pretty much active at night and sleeping during the day. >> then in the early '90s after attending a lecture on bats, he decided to change careers. >> i just started getting more and more into the idea of doing something for something else other than myself. the rock star thing is a little meggal omaniacal.

>> he decided to leave the rock world behind and start working with bats. >> when the baby bat is born -- >> he became a licensed -- a person who studies bats, and opened you the wildlife conservation center in new jersey. >> this is claudia. claudia is usually pretty tolerant of being handled. each bat has a different personality, different behavior, sometimes even a different look to them. >> over the last 25 years as an educator, one of his goals has been to make people less afraid of bats. because of that, he purposefully chose to feature fruit bats, native to africa, asia and australia. they're commonly known as the flying foxes. >> they are more attractive and more appealing to people. they look like my little flying chihuahuas i call them. they are much easier to use as educational subjects, and to get people's fears reversed. >> when the wing is around the

face like that, they're using their wings as built-in blanket. >> he is part of a larger movement that has been taking place in the last three decades in the united states, teaching people why these creatures should be protected, not feared. >> we're all here for one purpose and one target and one direction. that's to help these animals. to help people understand why they need our assistance. they're so much like us. they are different looking, different colors, different sizes, different shapes, different importances, different jobs that they do and i keep going back to, that is really what i think at the end of the day, makes me love them so much. they are like people. when life gets back to normal, go outside and look up and go and find some bats. now, simparica trio simplifies protection.

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every year, we, as a species, encroach deeper and deeper into bat habitat. and those of other wild creatures. exposing ourselves to new and dangerous viruses. with the dramatic increase in travel, rise in global trade, we're now capable of spreading those viruses, far and wide. scientists warn that what we have created is the perfect

storm for a new pandemic. >> we are, without a doubt, going to see more epidemics, like covid-19 or, perhaps, worse, unless we really change the way that we're interacting with our environment. >> the first major epidemic of the 21st century was sars, in 2003. other outbreaks, quickly, followed. in 2009, it was h1n1 or swine flu. 2012, mers. middle east respiratory syndrome. then, the large ebola outbreak in 2014. zika virus in 2015. and now, covid-19. >> they're increasing in frequency. they're coming quicker. they're going to spread quicker. they're going to infect for people. and they are going to cause more economic damage because we rely on that globalized economy, more and more each year. >> in a lab, nearly 6,500 miles from wuhan, researchers in berkeley, california, are

looking to bats to find clues on how to help humans fight coronaviruses, like covid-19. >> i think, in a way, there is actually a lot we can learn from bats. you know, this group of animals that's been around for millions of years. how can we look at their history with viruses and take that knowledge, and think about therapeutics and treatments, for ourselves? >> what is it about bats that allows some of them to host these viruses, without showing any illness? >> that's the question that cara brook is trying to answer. she began studying bats in madagascar in 2012. she and her colleagues are investigating how the bats' immunity keeps them safe from harm. >> i have always been fascinated by bats as host sources of infectious diseases that transmit to humans. in the case of certain bat species, they appear to be

perpetually primed to fight viral infection. >> scientists believe that understanding a bat's immune system can help develop a human battle plan for fighting these diseases, on a global scale. >> it's an opportunity. what is it about the bats' metabolism, or physiology? >> that might actually hold the answer for treating virus. >> if bats can handle thousands of different viruses, at a much higher load than humans can, let's find out why and use that. >> brook and her team infected the cells of two bat species with different viruses. then, they watched as the viruses spread and the bat cells mounted a strong defense. different than what would happen with humans. >> when a virus infects a cell, your immune response will recruit immune cells to the site to try and clear that infection.

>> and the signal to all sorts of cells that have not become affected, a virus is here, turn on your defense system. >> and typically, this manifests as inflammation. >> in humans, inflammation, oftentimes in the form of fever or swelling, helps fight infection. but too much or inflammation that goes on for too long can do more harm than good. it can even cause death. >> typically, more than half of the damage that results in disease tends to be the damage of the immune system attacking the host itself. and we call that immunopathology. >> that is actually how the disease starts. >> but bats' immune systems don't respond the same way as humans. >> it seems that bats are able to mount robust immune responses, but not experience that inflammation. >> some bat species are actually missing the genes that we, and other mammals, have that trigger the inflammatory process.

>> the adaptation. >> it doesn't appear that they get sick or very sick when they are carrying viruses that can be deadly in other people and animals. >> so could studying bat immunology help us, humans, create possible treatments to fight this current and future pandemic? what do you think is the greatest challenge, in terms of finding a treatment or cure? >> to my mind, the number of unknown viruses that are out there. i mean, we think there are about 1.7 million unknown viruses, of the type that can get into people. and we've got to get ready for these. find out what they are out there. get vaccines and drugs that affect, not just the one we know about but, the ones we're discovering right now. >> bats already contribute enormously to research that could one day be helpful to humans. they're being studied to see how they combat aging because they tend to live longer than other mammals their size.

research on bats is also helping the fight against cancer. scientists are trying to understand why bats don't develop tumors like other mammals. and now, the possibility that they could help us fight current and future coronaviruses. >> people are working on vaccines. they're working on drugs. that's what we're looking for. and i see it as an opportunity. >> many people are surprised by the physiological similarities between bats and humans, and the information that we may be able to extract from that. in addition to the antiaging and cancer research studies, scientists have also been looking into saliva of bats. it's got blood-thinning agents. scientists are looking to see if there could be blood-thinning insights that would be helpful for humans. in the meantime, researchers agree that it's our job to protect these extraordinary creatures and their habitats. because, as we learned from the

covid-19 pandemic, if we don't protect them, we're actually putting ourselves at risk. thanks for watching. good night. it is, admittedly, hard to say good evening at the end of a week that saw the worst day, yet, in terms of new coronavirus cases in this country. or the worst day ever, by far, in the state of florida. with nearly 9,000 new infections there. it is tough to end the day with 32 states now showing rising case counts. and just seven with declining numbers. harder, still. to look at that green line there for new cases in this country, and compare it to the european union, in pink. late today, diplomats told us that american travelers are unlikely to be allowed into member countries when