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This podcast from Science Friday talks about how West Nile Virus is spreading and is more likely to spread rapidly as temperatures increase and the disease's "goldilocks temperature" becomes more prominent throughout the globe. It says how humans have increased interaction with wildlife as well which increases the risk of humans contracting the virus and circulating it. The podcast also talks about different factors that go into West Nile Virus becoming more common, like with the lack of rainfall there are more infected mosquitoes.  It also says how the virus is extending into new areas where it wasn't before and is likely to keep spreading throughout the world. The changing environment is starting to affect mosquitoes and it changes how fast they grow, how long they live, and how frequently they bite people to get a meal.
This source brings attention to how bad disease cases are advancing, why it's happening, and how they affect everything around us.

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Segment Transcript

JOHN DANKOSKY: This is Science Friday. I'm John Dankosky. We all know the story of Goldilocks and the Three Bears, right? There are three beds. One is two hard. One is too soft. And one is just right.

Now, Goldilocks isn't the only one who thrives in these just right conditions. We've talked about the Goldilocks zone for planets. It's just the right distance from their sun to support life. Turns out some mosquitoes have their own Goldilocks zone too. At a certain temperature threshold, the mosquitoes that carry West Nile virus thrive.

As climate change makes our world warmer, more places are likely to fall into this Goldilocks zone for mosquitoes who carry the virus. Scientists expect West Nile cases will rise in the future alongside hotter temperatures. Joining me today to talk about this story is my guest, Melissa Bailey. She's a writer for Kaiser Health News, and an Environmental Journalism Fellow at the University of Colorado Boulder. Welcome to Science Friday, Melissa.

MELISSA BAILEY: Thanks for having me, John.

JOHN DANKOSKY: So Melissa, let's start by just talking about how many cases we've seen of West Nile virus in the state where you are, in Colorado, for instance.

MELISSA BAILEY: So cases actually tend to fluctuate from year to year. And that's because humans get West Nile virus from mosquitoes, which get it from birds. So the cases go up and down depending on these cycles of immunity in birds and in humans. But in Colorado last year, we saw 11 deaths and over 100 neuroinvasive infections. Those were the highest numbers in 18 years.

JOHN DANKOSKY: But next door in Arizona, it was a much different story, even more deaths and more cases.

MELISSA BAILEY: Yeah, the cases were through the roof in Arizona. There were over 100 deaths, and over 1,000 neuroinvasive cases, just way higher than previous years.

JOHN DANKOSKY: Now, we talked about this Goldilocks zone for mosquitoes. Explain to us a little bit about what that means. What is the zone the mosquitoes kind of thrive in?

MELISSA BAILEY: Well, the first thing to know is that mosquitoes are cold blooded, so they're very sensitive to outdoor temperature. It affects every aspect of how they function. The Goldilocks temperature is their favorite temperature, which is easiest to spread disease. So I talked to Ecologist, Marta Shocket, who studies mosquito-borne diseases.

MARTA SHOCKET: If it's too cold, you won't have enough mosquitoes. They won't be growing fast enough. It will take too long for the virus to develop inside the mosquito into an infection that can get to their salivary glands that they can pass on. The other hand, if it's too hot, they'll actually die too quickly. So it's this middle kind of Goldilocks temperature, not too cold, not too hot where mosquito borne diseases are best transmitted.

JOHN DANKOSKY: So how is that zone changing right now, Melissa?

MELISSA BAILEY: The mosquitoes favorite temperature is staying the same, around 75 degrees Fahrenheit. But Shocket found that 70% of people in the US live in places where average summer temperatures are colder than that Goldilocks zone. So as temperatures rise, scientists expect more people to live in climates where it's easier for mosquitoes to pass on West Nile.

JOHN DANKOSKY: OK. So more people in that zone, more mosquitoes in that zone, so we expect to probably see more of this disease. Now, as we've talked on the show in recent years about the state where you are living right now in Colorado, we talk about it a lot, because of drought, the severe drought that you've had there. Now, when I think of mosquitoes, I think of insects that thrive in very wet and humid climates. So explain to us the connection between West Nile virus and this drought.

MELISSA BAILEY: So you're right, John, mosquitoes do need water to breed. But yeah, it's counterintuitive. Research has shown that when there's more drought, there's more West Nile. And one big reason has to do with birds. So birds are important, because that's where mosquitoes pick up the virus and spread it to humans.

In really dry conditions, birds gather in greater numbers around these limited water supplies, so that brings them closer to the spots where mosquitoes hang out. And mosquitoes have more chances to pick up the virus from birds. So I talked to Dr. Desiree Labeaud. She's an infectious disease physician at Stanford University. She travels the world studying mosquito borne diseases. And I reached her in Kenya.

DESIREE LABEAUD: Every mosquito has its favorite place to call home. And for Culex mosquitoes, the mosquitoes that spread West Nile virus, they love stinky, standing water. So you can imagine if you have a lot of rain, that can actually wash away some of the developing eggs. But climate change can also promote a lot of drought. And having more drought could actually bring more West Nile, because you have more and more stinky, standing water, which isn't being washed away.

MELISSA BAILEY: So here, we have two theories, one about the birds, and one about water that are leading to more West Nile when we have drought conditions.

JOHN DANKOSKY: And now, West Nile virus for people who haven't followed very closely is a pretty serious disease, but it's not serious in all cases certainly. What exactly does West Nile do to the body?

MELISSA BAILEY: So most people who get West Nile virus, about eight in 10 don't have symptoms. The others typically get a fever, and other ailments, such as a headache, joint pain, vomiting, or diarrhea. And it's actually important to note that humans can't pass West Nile on to someone else. If a mosquito bites a person with a West Nile infection, and then bites another person, the second person won't get West Nile.

JOHN DANKOSKY: OK, so s doesn't spread that way, but it is spread through mosquitoes.

MELISSA BAILEY: It spreads from birds, to mosquitoes, to humans.

JOHN DANKOSKY: Tell us about the severe edge of this illness. How exactly severe can West Nile be in people?

MELISSA BAILEY: So some cases are called neuroinvasive. That's when the infection invades the brain, or spinal column, and can cause serious illness, paralysis, or even death.

JOHN DANKOSKY: But these severe cases of West Nile are pretty rare, right?

MELISSA BAILEY: Yeah, about one case in every 150 is neuroinvasive. It is rare. But Doctor LaBeaud told me once you see a case, you never forget it. And the risk of serious illness is higher for people with medical complications, and who are over 60-years-old.

And so that's people like Betsy Marston's husband, Ed, who died of West Nile a few years ago. Ed was 78. He loved to hike near their small town in Western Colorado. Betsy tells me that might be how he got infected, because he was older and recovering from heart surgery, he was at higher risk.

BETSY MARSTON: He had uncontrollable shaking. And there's nothing you can do about that. I mean, this disease was just rampaging through him. And he found it very, very difficult to talk. And when he did talk, he said, I'm just suffering through this. That was one of the last things he said. And then it went to his brain.

So it was hopeless. It's a brutal disease. It has no mercy. It just rips through your body and takes you away.

JOHN DANKOSKY: Wow, that's quite a story, and very sad. We've been focused here on Colorado where your reporting is, Melissa. But let's zoom out a little bit. We first saw this virus in the US back in the late 1990's in the New York City area.

And over the course of the last few decades, it's spread to other parts of the country. We probably haven't heard about it quite as much as other diseases in recent years. Did the researchers that you spoke with say if other parts of the US can now become vulnerable to West Nile?

MELISSA BAILEY: Yes, actually, every state in the mainland US has seen West Nile. These mosquitoes are everywhere. And some places in the US may get so hot that mosquitoes will die off quicker and spread less virus. But experts say overall, they expect West Nile infections to increase across the country due to temperature and drought.

JOHN DANKOSKY: Are there preventive measures that people can take to avoid getting this disease?

MELISSA BAILEY: Yes, so these mosquitoes love to come out in the summer at dawn and dusk. Some communities spray pesticide to kill the larva. And Betsy points out that there's a lot individuals can do to avoid getting bitten.

BETSY MARSTON: I can see we needed to be more vigilant. You need long sleeves. And you need to be aware of when you're outside. I don't go out at dusk anymore, and I used to never care.

It's unpredictable what's happening in our climate now. But we do know that West Nile is here. It's dangerous. And we have to protect ourselves and be aware of it.

JOHN DANKOSKY: Yeah, so just staying away from mosquito bites is something I remember from the first West Nile outbreak. Melissa, as the world gets warmer, I assume that this isn't the only disease that we're following that could migrate and wind up in places that it hasn't been, because the climate is changing.

MELISSA BAILEY: Yes, John, it's already happening. Lyme disease is a great example. There's evidence that the ticks that spread the disease have already expanded their range due to climate change. And scientists expects ticks to keep marching north and coming out earlier in the year with hotter temperatures.

There's also Dengue fever, a tropical mosquito borne virus. And scientists expect Dengue to expand its reach in the United States. And then there are all these waterborne diseases that spread more easily with heavy rainfall, or warmer water. One of those is called Ciguatera fish poisoning. It gives people gastrointestinal trouble, and this weird symptom where your sense of hot and cold can be reversed.

It's kind of wild. It's been popping up in the Gulf of Mexico. And it's expected to spread further as oceans get hotter.

So there are many examples of how human-caused climate change is already making people sicker. And scientists are warning us that as we keep heating the planet, many diseases will spread to new locations, and get more people sick. And just one thing to keep in mind is that these diseases hit hardest on vulnerable groups, which often includes children, the elderly, communities of color, and people with low income.

JOHN DANKOSKY: Yeah, and that's something especially to watch. In areas in the West, there's Indigenous communities, other places where health outcomes have already been relatively poor, and more disease spreading across some of these areas could really have a huge impact.

MELISSA BAILEY: Yeah, and it's often the people who are least culpable for climate change that are feeling the largest impacts on their health.

JOHN DANKOSKY: Melissa Bailey is a writer for Kaiser Health News, and an Environmental Journalism Fellow at the University of Colorado Boulder. Melissa, thank you so much for sharing this story with us.

MELISSA BAILEY: Thanks so much, John.

JOHN DANKOSKY: And you can read the full story on our website sciencefriday.com/westnile.
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Why Climate Change May Bring More West Nile Virus To The U.S.

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Segment Transcript JOHN DANKOSKY: This is Science Friday. I'm John Dankosky. We all know the story of Goldilocks and the Three Bears, right? There are three beds. One is two hard. One is too soft. And one is just right. Now, Goldilocks isn't the only one who thrives in these just right conditions.

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This article from Environmental Epidemiology talks about how noncommunicable diseases are becoming more of a problem. It uses the recent Covid-19 pandemic and looks at how it connects to our economy, international trade, politics, peoples opinions and behaviors, and social inequality. The article not only talks about how the environmental problems that humans cause but the other effects that diseases have on society. According to the website, climate change is projected to affect infectious disease patterns. The source connects how infectious diseases, pandemics and climate change also have an effect on growing social problems like racism as well as political issues.

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Infectious disease, the climate, and the future : Environmental Epidemiology

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virus itself, but rather that it may compound with other and more serious crises. Climate change will likely affect human health, economy, and the society more than disease outbreaks. Governments at all levels, from local to international, can chart a greener, healthier, and equitable course for the…

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This article from News Medical talks explores the topic of Malaria and how the growing climate change has horrible effects on those with Malaria. According to the website, rising global temperatures are breeding new and more aggressive mosquito-borne diseases and making existing ones even worse. The constant warm weather is making mosquito lifespans slowly increase which also increases the risk of transmission of diseases like Malaria.
Current data suggest that increases in temperature, humidity, and rainfall are helping to expand the mosquito population at northern locations. This is allowing it to emerge in new locations which had previously not supported mosquito populations. The article also mentions El Nino and how different rainfall patterns are helping breed more mosquitoes. Finally, it mentions many solutions to try and combat this widespread problem.

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The transmission of malaria is heavily influenced by environmental events. Recently, scientists have described the disease as involving a complex interplay between humans, mosquitoes, the plasmodium parasite, and the climate.

Image Credit: Digital Images Studio/Shutterstock

Now, as the topic of climate change heats up, scientists and global health organizations are emphasizing the importance of implementing strategies to curb climate change in order to prevent an increase in many health problems, including the spread of infectious diseases such as malaria.

Data is emerging that supports the link between the transmission of malaria and climate change, and some scientists have suggested that the world will experience elevated transmission of the disease without significant action taken against climate change. Others suggest that malaria distribution will not be hugely affected by increasing temperatures, but that other diseases carried by mosquitoes, such as Dengue fever, may be more worrisome. Meanwhile, other environmental changes such as deforestation are also expected to change the distribution of mosquitos, and therefore affect the spread of mosquito-borne diseases.

Here, we discuss how environmental events influence the transmission of malaria.

Malaria, although preventable, kills over 400,000 annually

Recent figures reveal that there were an estimated 229 million cases of malaria worldwide in 2019 and that around 409,000 lost their lives to the disease. According to the World Health Organization, those most affected by malaria are children under five (who accounted for 67% of all malaria deaths in 2019), and those in Africa (who accounted for 94% of all cases in the same year).

The life-threatening disease, however, is preventable and curable. Research has shown that vector control is an effective way to prevent and limit the transmission of malaria, with insecticide-treated mosquito nets and residual indoor spraying being the two major forms of vector control.

Although these forms of prevention exist and are encouraged in areas where the disease is most prevalent, data collected over recent decades has shown that environmental change is producing environmental conditions that favor the spread of malaria, which may be offsetting the impact of preventative measures and putting more people at risk.

Climate change influences the transmission of malaria

Changes in temperature, humidity, rainfall, and other climatic conditions have an impact on important factors that dictate the transmission of malaria, such as the lifespan of the mosquito and the development of malaria parasites in the insect.

According to NASA, nineteen of the warmest years on record have occurred since 2000. Together, 2020 and 2016 have been the warmest years since records began in 1880. Data shows us that global average temperatures have been steadily and significantly rising over the past century, with accelerated increases observed since the 1950s, demonstrating the trend is hastening.

Scientists believe that mosquito-borne diseases are benefiting from these rising temperatures and the other climatic changes they induce. The warmer climate is facilitating the geographical distribution of mosquito-borne diseases such as malaria, as well as the risk of transmission.

Data suggests that increases in temperature, humidity, and rainfall (all caused by climate change) are helping to proliferate the mosquito population at higher altitudes. This is widening the geographical distribution of the disease, allowing it to emerge in new locations which had previously not supported mosquito populations.

Additionally, increases in temperatures at lower altitudes, where mosquitoes and malaria are already prevalent, have the impact of adjusting the growth cycle of the parasite that causes the mosquito to carry the disease, allowing it to develop malaria faster and, therefore, increasing transmission rates.

The El Niño climate cycle that impacts global weather patterns is greatly influenced by climate change. Scientists have already highlighted the link between alternations to the cycle and the transmission of mosquito-borne diseases including malaria, dengue, and Rift Valley fever.

Additional rainfall that can result from changes to the El Niño cycle can provide good breeding conditions in locations that are usually dry, allowing the insect and, therefore, the disease to proliferate in new regions.

On the other hand, droughts caused by changes to weather patterns in conjunction with increased humidity can also result in the proliferation of mosquito populations. In this case, rivers can be converted into strings of pools which provide the optimal breeding site for mosquitoes.

Further to this, changes to the El Niño cycle that cause areas significantly impacted by malaria to become drier can lead to increases in malaria cases due to the loss of heavy rainfall that can wash away mosquito breeding sites. Data has shown, for instance, that dry conditions associated with El Niño were linked to a one-third increase in malaria cases.

Climate Change x Malaria | A RBM Partnership to End Malaria Explainer Video

What are the solutions?

Ultimately, climate change must be addressed in order to prevent a multitude of global health problems. This includes the potential for the exacerbated spread of vector-borne diseases such as malaria. The influence of both climate change and other environmental changes on vector-borne disease is a significant threat that could be prevented with the right action.

History has shown us that social factors can often be adjusted to offset the impact of increasing global temperatures, for example, the Europe endemic malaria which was eliminated in 1975 through improvements to socio-economic conditions, irrigation and drainage, the establishment of new farming methods, and better healthcare. However, whilst social improvements can make a difference, they are more difficult to achieve in developing regions that are most heavily affected by the disease.

Whilst researchers are not yet sure of how dramatic the impact of climate change will be on malaria specifically and how controlled its spread into other geographical regions can be, it is clear that this is something that needs to be monitored.

Meanwhile, malaria still exists as a very immediate threat that causes huge numbers of preventable deaths every year. Research and funding into malaria need to continue to provide current and improved treatment to those who are most vulnerable and to monitor how the distribution of the disease is changing, be it through climate change, zoonotic changes (such as the malaria species that has developed in monkeys) or antimalarial drug resistance.

References

Caminade, C., Kovats, S., Rocklov, J., Tompkins, A., Morse, A., Colón-González, F., Stenlund, H., Martens, P. and Lloyd, S., 2014. Impact of climate change on global malaria distribution. Proceedings of the National Academy of Sciences, 111(9), pp.3286-3291. https://www.pnas.org/content/111/9/3286

Global Temperature. NASA. Available at: https://climate.nasa.gov/vital-signs/global-temperature/

Lubinda, J., Haque, U., Bi, Y., Hamainza, B. and Moore, A., 2021. Near-term climate change impacts on sub-national malaria transmission. Scientific Reports, 11(1). https://www.nature.com/articles/s41598-020-80432-9

Malaria. World Health Organization. Available at: https://www.who.int/news-room/fact-sheets/detail/malaria

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The transmission of malaria is heavily influenced by environmental events. Recently, scientists have described the disease as involving a complex interplay between humans, mosquitoes, the plasmodium parasite, and the climate.

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This article from the CDC, which is the nation's public health leader, focuses on all the different infectious diseases and how climate change affects each of them. Including how contact with animals has increased as human development and climate change have moved animals into new habitats with new viruses carried by and to humans. The article also talks about water and fungi infiltrating new areas with rising temperatures and increased flood amounts. The CDC article, also gives sources, administration groups, and solutions to how humans can try to stay safe and prevent diseases from spreading by spreading awareness of climate change. According to the CDC, more investment into research, public health, disease surveillance, and analysis tools are needed to try and stop or at least slow down the rapidly changing planet and climate change

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Download the full version of this page [PDF - 4 pages]
Our Risk For Infectious Diseases Is Increasing Because of Climate Change
As the nation's public health leader, the Centers for Disease Control and Prevention (CDC) is actively engaged in a national effort to protect the public's health from the harmful effects of climate change. Scientists from CDC's National Center for Emerging and Zoonotic Infectious Diseases (NCEZID) are at the forefront of many of these efforts. This report highlights some of that work and also looks ahead to the important work yet to come.
Lyme disease, West Nile virus disease, and Valley fever. These are just some of the infectious diseases that are on the rise and spreading to new areas of the United States. Milder winters, warmer summers, and fewer days of frost make it easier for these and other infectious diseases to expand into new geographic areas and infect more people. To understand climate change's impact, it's important to look at some of the common ways these diseases spread-through mosquito and tick bites, contact with animals, fungi, and water.

As the climate changes, the risk also increases for health threats such as:

Anaplasmosis

Anthrax

Antibiotic-resistant infections

Cryptosporidiosis

Dengue

Ehrlichiosis

Fungal diseases like valley fever and histoplasmosis

Giardiasis

Hantavirus

Harmful algal bloom-associated illness

Lyme disease

Plague

Rabies

Spotted fever rickettsiosis

Salmonellosis

Vibriosis

West Nile virus disease

Mosquitoes and Tick Bites

Mild winters, early springs, and warmer temperatures are giving mosquitoes and ticks more time to reproduce, spread diseases, and expand their habitats throughout the United States. Between 2004 and 2018, the number of reported illnesses from mosquito, tick, and flea bites more than doubled, with more than 760,000 cases reported in the United States. Nine new germs spread by mosquitoes and ticks were discovered or introduced into the United States during this period. The geographic ranges where ticks spread Lyme disease, anaplasmosis, ehrlichiosis, and spotted fever rickettsiosis have expanded, and experts predict that tickborne diseases will continue to increase and perhaps worsen. Longer, warmer summers have also given mosquitoes more time to reproduce and spread diseases. In 2012, a mild winter, early spring, and hot summer set the stage for an outbreak of West Nile virus disease in the United States, resulting in more than 5,600 illnesses and 286 deaths.

Contact With Animals

Climate change has forced some animal species into new habitats as their natural habitats disappear, and it has expanded the habitats of other animals. This movement of animals into new areas increases opportunities for contact between humans and animals and the potential spread of zoonotic diseases, as these examples show:

Wildlife carrying the rabies virus are expanding to new geographic areas of the country.

Arctic temperatures are rising more than twice as rapidly as the rest of the world. Warming temperatures in Alaska have led to increases in vole populations, which can spread diseases like Alaskapox to humans.

As global temperatures rise, deadly diseases that are a threat in other countries - like Ebola, Lassa, Rift Valley fever, and monkeypox - will increase along with the risk of them being imported into the United States.

Fungi

Rising temperatures have allowed certain disease-causing fungi to spread into new areas that previously were too cold for them to survive. For example, Valley fever - caused by a fungus that lives in the soil in hot and dry areas - has already spread into the Pacific Northwest. This fungus can cause severe infections and death and is often misdiagnosed and treated inappropriately. As the difference between environmental temperatures and human body temperatures narrows, new fungal diseases may emerge as fungi become more adapted to surviving in humans. Climate change also increases the risk for natural disasters and flooding, which can increase the risk for mold to grow in people's homes. Certain molds can cause deadly infections of the lungs and brain.

Water

Scientists predict that climate change will have devastating effects on freshwater and marine environments. For example, we could see more frequent and more severe instances of harmful algal blooms, which are the rapid growth of algae or cyanobacteria in lakes, rivers, oceans, and bays. Warming temperatures in Lake Erie have contributed to extensive toxic blooms that last into the early winter months. Harmful algal blooms can look like foam, scum, paint, or mats on the surface of water and can be different colors. They endanger our health when we eat contaminated shellfish. They also can harm pets, livestock, wildlife, and the environment. While no human deaths caused by cyanobacteria have been reported in the United States, some of these toxins can make dogs and other animals sick and possibly even cause death within hours to days. Dog deaths have been reported after dogs swam in or drank fresh water containing cyanobacterial toxins.

Additionally, scientific evidence shows that traces of antibiotics are present and can sometimes remain in the environment (waterways and soils) for a long time. Scientists need to do more research to better understand the connection between the environment, existing and emerging antibiotic resistance and its spread, and the impact on human health.

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Download the full version of this page [PDF - 4 pages] As the nation's public health leader, the Centers for Disease Control and Prevention (CDC) is actively engaged in a national effort to protect the public's health from the harmful effects of climate change.