You might be sitting in the park or by the pool. You could be on a hike, maybe in your car even, when you hear it. There's a mosquito somewhere nearby. Some think of them as just another summer pest, but truth is humanity has been at war with mosquitoes since the very beginning.

They have been the biggest killer of humanity across our existence.

And there's a lot more at stake than just itchy bumps.

You remove that mosquito species and the pathogen evolves. And now this mosquito species, which didn't transmit pathogens before can now transmit malaria.

That's Dr. Timothy Winegard. He's a historian and professor at Colorado Mesa University. He's also the author of a fascinating book called The Mosquito, A Human History of Our Deadliest Predator. Today, he's joining me to talk not just about their annoying and deadly past, but also how to avoid mosquito bites and the diseases they may carry, and even why some people are more attractive to mosquitoes than others. Here's a little hint: it might have something to do with your blood type. I'll tell you all about it. I'm Dr. Sanjay Gupta, CNN's chief medical correspondent, and this is Chasing Life.

It's an amazing book and I'm just so curious because as a doctor, someone who's interested in public health, I've been interested in mosquitoes for a long time because of their obvious impact on global health. You're a historian, so how did this come about for you?

'Well, I had written four books previously on, you know, kind of the minutiae of academia and indigenous peoples and warfare, military history. And after my fourth book, I sat down with my dad, who's an emergency physician, uh, back home in Canada. He said, well, you should write a book of malaria. And I kind of disparaged him and said, sure dad, I'll write a book on mosquitoes. And I started researching, um, the historical impact of mosquito-borne pathogens across our human existence. And once I kind of went down that rabbit hole, it was amazing.

Yeah, I think that was, there was a lot of fascinating parts of the book, but that part of it I think was the most interesting, the idea that mosquitoes have had such an impact on our shared human history. That surprised me a bit. I mean, again, the idea that these little pesty little creatures cause so much human suffering and death. I knew that, although a lot of people don't realize that, just how significant that is. But the impact on history, wars, whether or not certain parts of the world were going to be conquered or not. Is that what surprised you the most as well?

I think just some of the stories, for example, Scotland giving up its independence with the acts of union to England because of a failed colonial expedition in Panama that was cut to pieces by mosquitoes in yellow fever or, you know, the surrender of General Cornwallis at Yorktown or the African slave trade or the fact that, you know, because northern hemisphere countries don't have endemic malaria, they're able to develop more affluent economies because they're not continuously suffering from malaria. It's more seasonal in the northern countries.

The thing that sort of struck me is DEET, just those types of broad sort of insecticides and things like that. When you look historically, how big an impact has that had? You know, spraying large areas of the country with, you know, protective agents, potentially toxic agents. How much of an impact did that have?

So seemingly they're able to circumvent all our frontline weapons and relatively quickly They evolve very quickly and so too does malaria which is why it's still the scourge of humanity. It's important to note too for your listeners that of the 3,700 mosquito species there's only a couple hundred that are capable of transmitting or vectoring those pathogens and most don't do it very well at all and it's also important to know that a mosquito untethered from a pathogen is harmless.

Right. And so these potential pathogens that they're carrying, they are just the carriers of this. And it is those pathogens that are really the fundamental harm. I mean, mosquitoes are irritating, but it's what they potentially could do to us in terms of transmitting disease that you're really focused on. Can you give some context for this? Obviously malaria is the big one, but West Nile, Zika, Dengue, just provide some context of how significant mosquitoes are in public health.

'So the simplest way to classify mosquito-borne pathages is in three groups. The first one is worms that are transmitted by mosquitoes that block the lymph nodes in the lymphatic system of humans. And canine heartworm, if we love our dogs, that's caused by mosquitoes as well or transmitted by mosquitos. The second one is the virus class, which is yellow fever, West Nile, dengue, all the encephalitis. Eastern equine encephalitis, Venezuelan encephyllitis. But the fastest growing mosquito-borne pathogen is dengue, which is in this virus class and roughly four to five billion people are on the planet currently are at risk of dengue which is known as breakbone fever. Um, and then the third is malaria, which is a very sophisticated, uh, protozoan parasite. Um, which again, there's, there're five human malaria is, but amphibians, reptiles, all the birds were all infected with, with malaria, which, uh, evolved 400 million years ago from an aquatic algae.

And, you can see where we're sort of gonna go with this conversation, if there weren't mosquitoes, is the thinking, obviously we don't know for sure, but is the thinking that those pathogens might spread in a different way?

We don't know, and that's part of the dilemma with CRISPR and using gene drives in genetically altered mosquitoes and releasing them into the wild to either create stillborn offspring or only male offspring, thereby bringing down that specific mosquito species. So we don't, and again, sometimes, uh, often the case is we are our own worst enemies when it comes to certain factors in our in our societies whether that's the dawn of agriculture, which Jared Diamond calls the worst mistake humanity ever made, or climate change with fossil fuels. So there's so many unanswered questions when we look at CRISPR and gene editing in in the field of mosquito research.

'Let me just go back to the war on mosquitoes that you sort of outlined in the book. There were cities in the United States, New Orleans, for example, Philadelphia, Boston, that used to be dramatically affected by many of these mosquito-borne illnesses, yellow fever. And now we don't hear about it very much, certainly in those places. Don't really hear about it at all unless there's imported cases. So what does that mean? What's the lesson there? Because those cities obviously have been able to control this.

So I think when we look at our war with mosquitoes, it's twofold. We can attack the delivery system, which is that specific mosquito species, or we can try to attack the pathogen itself. The surgical use, if you will, of DDT to spray around windows and doors and screens for houses and then attack, you know, mosquito breeding grounds and standing water actually cause very little environmental degradation. What happened is when DDT was commercialized in 1949 for farmers globally, they literally carpet bombed the planet with DDT. And so what happened is the average mosquito species became immune to DDT within seven years. So when America bans DDT and the rest of the world follows in the early 70s and mid 70s, it's not so much because of anything Rachel Carson wrote or environmental concerns. It's simply the fact that it didn't work anymore. Mosquitoes were became immune to DDT.

So how worried are you, how worried should we be then? Because you describe an environment where some of what have now been sort of referred to as tropical diseases are finding their way increasingly north. I think you're saying because of the way that the climate is changing. How worried to the average person be, for example, living in the United States?

'I think the problem with a lot of diseases or pathogens, if it's out of sight, it's of mind, and then money doesn't go towards either eradication or research for these pathogens and malaria, certainly is one of those where it's viewed as an African disease or a disease of, you know, countries that are not as affluent as the Western world or the Northern countries, if you will. So I think there is a bit of a wake up call when we are going to start seeing transmissions of- or epidemics of chikungunya, dengue, maybe even malaria in the United States. In most of the books I've read and looking at the dialogue about the banning of DDT, certainly there was some knowledge that it caused cancer and was passed down the food chain, but largely it was it just didn't work anymore. So we're not gonna use something that doesn't work any more.

Is there a version of this that could work? What else do we have in our toolbox?

The efficacy of DDT has come back because mosquitoes have lost their immunity to it in certain places. So some countries are actually proposing the reintroduction of DDT for use again on screens and bed nets or around doorways. And, and, and obviously vaccines are trying to be developed. The yellow fever does have a vaccine. Um, it was created by a South African American just prior to the second world war, but other than that, where malaria is again, is not a a virus in a traditional sense. So traditional vaccines don't work for malaria, but there is research and field studies on malaria vaccines, certainly really in the last 10 years. And then CRISPR, as we had mentioned, gene editing mosquitoes and releasing them in the wild to bring down that mosquito species.

'So before we talk about that possibility, because I am intrigued by that and I've done a lot of reporting on various uses for CRISPR, but there's a couple points you make about this in the book, but just before we get to that, are there things that mosquitoes are good for? I mean, is it critical to have mosquitoes as part of our overall well-functioning environment?

Yeah, and again, it's important to note that nobody is promoting the eradication of all mosquitoes from the planet. But mosquitoes are pollinators. Females bite to secure blood, a blood meal to grow and mature their eggs and just be a good mom. But mosquitos are pollinaters. They drink pollen. So the head of the American Orchid Association actually sent me an email when I was researching and said that if we eradicated a certain mosquito species or mosquitoes then certain species of orchids would actually go extinct because they're only pollinated by mosquitoes. So I'm a big Star Wars fan and I kind of equate it to a balance to the force and when you disturb the balance to the force there's unintended consequences like the rise of the Sith. So mosquitoes provide food for birds, bats, fish, and so they're vital to healthy ecosystems. And again, when we start tinkering with the natural homeostasis of ecosystems, there can be consequences that are either unintended or may be known about, and we do it anyway.

We're gonna take a quick break here, when we come back, we'll talk about the do's and don'ts of mosquito bite prevention.

It's really interesting to just sort of think about this philosophically, that it's sometimes hard to predict the downstream effects of whatever you may do. So where do you come down on the idea, then, of even eradicating certain species of mosquitoes? Because even if it's not all mosquitoes, those mosquitoes may have some benefits to to our ecosystem.

Right. And I don't take sides on this point that as the book is about, the mosquito is the number one killer of humanity across our existence by far. It far outpaces human beings. So mosquitoes or the pathogens act as a Malthusian check on unbridled human population growth as well. I mean, that's largely the function that mosquitoes have served is to, for lack of a better word, dispose of humanity, so, perhaps that is a function of mosquitoes is to check population growth for humans, given that we don't really have other natural predators other than ourselves or other pathogens. There is usually two sides to everything. One is it would certainly reduce immense amounts of suffering specifically of children because the malaria burden 90% of the malaria burden falls on children under the age of five because their immune systems just can't handle the overload of the pathogen and pregnant women to that point too. But also the danger is if we remove that mosquito species, will the pathogenic evolve to be able to transmit by another mosquito species? And it just fills the void somewhere else.

But just to table set for a second, you're not opposed to finding treatments and maybe even vaccines or cures for malaria.

I think it is the right thing to do. How we do that, I suppose, is the question, whether it's through vaccines. And again, as you know, with CRISPR, there's just so many unanswered questions and potential pitfalls with the use of CRISPR. Whether that's on the mosquito or dire wolves, or anything else for that matter. That one, I'm not sure about.

Yeah, look, I think there's gonna need to be significant guardrails around this. Let me ask you, so first of all, after you wrote the book and you did this deep dive, did you live your life any differently in terms of just avoiding being bitten by mosquitoes?

No, they're just a kind of a part of life. Um, I actually gained a respect for mosquitoes, if anything. Um, and I also don't get bitten very much. So if you put my sister here, she'd have a thousand bites and I might have one or two, so when they land on me or I see them or, you know, they buzz, I have more of a, I guess, a greater respect for mosquitos and I, maybe won't go so far as to use the word love, but they're a remarkable creature. And highly sophisticated, highly evolved. I don't kill them anymore if I don't have to.

Why, I'm sure you must have asked, why are they going after your sister and not you?

'So 85% of what makes the individual person more or less alluring to mosquitoes is hardwired in our genetics. So unless you're gonna CRISPR yourself, you can't get rid of that. It has to do with blood type. So blood type O is their vintage of choice and people with blood type O on average get bitten twice as much as people with blood type A and blood type B falls somewhere in between. It has do with the bacteria on your skin, how much of certain bacteria you have, your body odor, lactic acid, how much carbon dioxide you emit, your body temperature, so there's a lot- which is why they go after pregnant women because their body temperature is slightly elevated. So that is why they prefer some people over others. And again, they hunt by both sight and smell. So they can smell carbon dioxide. So if you're exercising or breathing heavily, they'll smell that and be attracted to it. And they also think of kind of night vision goggles almost. They see heat signatures. So they're a miraculous creature. And again, it has to do with your biological genetic makeup. And then the 15% that is not genetic is clothing you wear. They like dark clothing. Fragrances, if you apply fragrances, they're attracted to fragrances. So a little bit is within our control. But it's better to be stinky, like don't shower, except clean your feet. The bacteria on our feet, which is the same one that ripens a lot of cheeses, is an aphrodisiac to mosquitoes, which is why we find we get bit around the feet and ankles a lot, is because of our bacteria on your feet.

So first of all, I am blood type O, I like to work out. It's pretty hot where I live. When I'm working out, I'm breathing a lot of CO2. So based on all those things, I'm probably a bit of a magnet for mosquitoes.

'Yeah, and I mean, that's not a, it's not fool- some people with blood type O obviously, my sister is blood type O, so I mean she, and she gets devoured on blood type B and I get the odd one, but they don't generally like me. So the easiest things to do obviously are just cover up and don't go out at dusk when they are feeding or primarily feeding. Um, citronella candles really don't work. The ceiling fans on your porch do work like moving air works like fans. Um, deet does work, but again, I don't use mosquito repellent, but I know people who lather themselves in it, but they miss this little spot on the back of their calf and she'll find the chink in our armor. I mean, again, she's-

I just assumed there was a halo effect if you had deet on, but you're saying even a small patch of skin?

Yep, they can still still be a target.

I've heard if you're drinking beer, you're a bigger target, true?

So drinking alcohol raises your body temperature slightly. So again, yes, given the way they hunt with the scent of the CO2 and then kind of an infrared heat signature. So when your body temperatures slightly elevated from drinking, they will then come after you and instead of me.

So again, so 85% of that you're saying is sort of hardwired, if you will. How big a predictor is blood type O compared to how much CO2 I produce or what kind of bacteria might be on my skin? Is that the biggest sort of predictor?

Um, and all the research that I looked at blood type was a huge predictor.

'This is good data you're citing. I mean this isn't just anecdotal observation-

No, no, this is scientific method research. Studies done, whether it's all over the world, on blood type and CO2, bacteria, lactic acid, all those genetic factors that go into it. So it's not simply one or another. It's kind of the combination of the package of genetics.

Deet seems to have mixed sort of, you know, people have mixed sorts of thoughts on deet. Some people think of it as very toxic. They prefer the organic bug sprays, things like that. Where do you come down on all that?

Uh, I don't use any bug spray. Uh, the only time I used deet was in the military training in New Brunswick in Canada, which in the spring it was, I mean, we were outside for what, three, four months training and it was vicious. I don't know if there's any studies either way that are conclusive to, you know, it's a carcinogenic or that it really doesn't harm us. So, I may, you may know more about that than I, than I do. Um, it does work. Um, I will say that.

Well, it works and it also seems to be recommended by large medical organizations, especially if you're going through mosquito infested areas. They will say use an insect repellent with deet.

Yeah. And, and I suppose if you're going into regions where, you know, there's, you know, dengue or malaria or yellow fever, I'd rather use it for, you know, three weeks in Cambodia than, than get dengue. Um, so that's my personal opinion only obviously.

Are you, based on just everything you've read and people you've talked to, are you optimistic that there'll be a malaria vaccine? I mean, you said it's a very tricky pathogen. What do you anticipate?

'I am optimistic actually because we're starting to see more interest in it and more money going towards research, whether that's from government organizations or the Gates Foundation or academic organizations. So the problem is, is right now it's a multi-shot vaccine and we know even with our COVID experience of getting the shot and then the booster, people don't necessarily want go back for a second one or, you know. So there's a lot of work that still needs to be done and the efficacy rates seem to be seem to fall quite precipitously with the more recent ones. But given, I guess, this increasing awareness and more attention being paid to even if it's slightly marginal compared to what it was, I do have hope for a malaria vaccine within the, you know, near future, next decade. Um, given the research and not just one group of academics or researchers working, there's multiple organizations working on various vaccines. So I'm optimistic.

And I hope whoever is listening that may be involved with that kind of research knows I think how important it is, but also to make sure just to say it from the outset that it's gotta get to the people who need it and who would benefit from it the most. I mean, I think it's one of the challenges always with these incredible new medical technologies is that sometimes the people who would most benefit don't always have access. And I'm not trying to be preachy, but what a shame it would be for it potentially to be out there and not giving as much benefit as it could. Overall, do you think we're winning or losing our war with mosquitoes, as you describe it?

I think we're winning, but it's a protracted war and it's been going on across our existence. If we look at specifically, I mean, yellow fever rates are obviously way down from what they were prior to the vaccine during kind of the 1600s, 1700s during colonization. I mean yellow fever ran amok. So malaria rates are also decreasing annually over the last kind of 10 to 20 years, which is a very good thing. But again, dengue rates are increasing and West Nile rates are increasing, so there's a bit of a give and take. But if all is equal, the chances the death rates from dengue and West Nile, I mean, they don't even compare to malaria or yellow fever. So I would like to say we are winning. And then we'll see what happens with, as you just mentioned, vaccines for malaria, Wolbachia bacteria with mosquitoes specifically for dengue. And then West Nile is fairly benign anyway, so it's not a huge concern.

Well, congratulations, I mean, really, it's such an enormous, audacious process to write something like this and you spend years doing it and I congratulate you on getting it done, but then also the tremendous success of the book as well. You know, it is such an important topic and as you mentioned at the beginning, it was kind of remarkable to me that there wasn't more written about it considering how much mosquitoes have impacted us. From a health standpoint, sure, but historically. That was, that part of it was really interesting to me. I didn't know it. I learned a lot from you, so if your goal was to teach, you know, consider me one of your students and thank you for that.

Well, thank you. I appreciate that. And as I said, I learned a ton from, from it as well. So I benefit from it like everybody else. So thank you.

Well thank you for spending some time with us.

Oh, I'm happy to be here. Thank you. I appreciate the invite to come chat with you.

That was my conversation with Dr. Timothy Winegard. Now I do know for many of you, the big question still is, how do I stop mosquitoes from biting me? So don't worry, we're gonna dig into that more on Tuesday's episode, including more information on deet. Thanks so much for listening.