Mosquitoes flourish and bring deadly diseases to new areas. Here’s a big reason why


There are very few winners in the climate crisis, but scientists are pretty sure there will be at least one: Mosquitoes.

These insects – annoying at best, deadly at worst – thrives in heat and humidity. As climate change causes more frequent and more severe heat waves and storms and floods that leave behind pools of stagnant water where most race, it’s boom time for mosquitoes.

For the first time in decades, the US Centers for Disease Control and Prevention is warning of more cases of locally acquired malaria in the United States – news that thrust mosquitoes into the spotlight. While it is too early to know whether these specific cases are linked to climate change, scientists have warned that malaria could become more common in the US as temperatures rise there.

It has raised new concerns about pushing mosquitoes into regions where they haven’t been for generations — or ever — and what that could mean for the spread of the deadly diseases they carry.

An Aedes aegypti mosquito under the microscope at the National Environment Agency's mosquito production facility in Singapore.

The increase in temperature allows mosquitoes to grow faster and live longer. Whereas before they died out during harsh winters in many places, they now have a better chance of surviving and longer to build their population. Heat also speeds up the time it takes for a parasite or virus to mature inside a mosquito.

“The warmer the temperature gets, the shorter the process becomes. So not only do these mosquitoes live longer, but they can potentially become infected earlier,” said Oliver Brady, associate professor at the London School of Hygiene and Tropical Medicine.

They also get other benefits from the heat. When it’s warmer, more people tend to be outside in the morning and late afternoon – prime time for mosquitoes.

The heat is also pushing cities to increase their green space, which has a vital cooling effect, but could also provide ideal new breeding grounds for blood-sucking insects.

In the U.S., the number of “mosquito days” — those with the warm, humid conditions they love — has increased across the country, according to a recent study. analyze from Climate Central, a nonprofit research group.

The researchers analyzed more than four decades of data at nearly 250 locations and found that more than 70 percent of them have become more hospitable to mosquitoes.

While most of the approximately 200 species of mosquitoes in the U.S. are harmless, there are about a dozen that can transmit diseases to humans, including chikungunya, dengue, zika and West Nile viruses.

A pair of Aedes albopictus mosquitoes are seen during a mating ritual.

While serious mosquito-borne diseases remain rare in the US, other countries are not so lucky.

In sub-Saharan Africa, where malaria has had devastating consequences, climate change is helping mosquitoes significantly expand their range, according to recent research.

Anopheles mosquitoes that transmit malaria have moved, on average, to higher altitudes by about 21 feet per year and southward by nearly 3 miles per year, a Georgetown University report found.

It’s a pace that tracks climate change and could have significant consequences for areas that have never experienced malaria before and are likely to be unprepared, said Colin Carlson, a global change biologist at Georgetown University and co-author of the report. .

Dengue fever is another potentially deadly disease viz ready to grow in a warmer world.

Also known as “bone fever,” it causes fever, nausea, vomiting, fatigue, and diarrhea, and in some cases, internal bleeding and death. There is no cure or specific treatment for dengue, leaving sufferers with no other option but to eliminate the symptoms.

Peru is currently experiencing its worst outbreak of mosquito-borne dengue fever in history, which has infected and killed an estimated 150,000 people. more than 250.

Experts said the unusually high levels of rainfall and heat provided ideal conditions for mosquitoes. Although scientists have yet to assess the role climate change played in the outbreak, Carlson said the links seem clear.

“I’m not a betting man, and I’d put money on when we go and do that study, it’s going to be climate change,” he said.

A worker fumigates a house against the Aedes aegypti mosquito to prevent the spread of dengue fever in a neighborhood in Piura, northern Peru, on June 11, 2023.

Now dengue is knocking on the door of Europe and USA.

A billion new people will be exposed to the right weather conditions for dengue transmission, and most of those people are in Western Europe and the United States and temperate China,” Carlson said.

Were outbreaks spread locally in Texas, Florida, Hawaii and Arizona. And last week, the European Center for Disease Prevention and Control ADVISED that the Aedes albopictus species – which can transmit dengue and chikungunya – is pushing north and west in Europe as climate change grips the globe the fastest warming continent.

“What’s surprising is the speed of spread,” Celine Gossner, senior expert on emerging and vector-borne diseases at ECDC, told CNN. In just a decade, the number of regions where this mosquito is established has tripled, she said.

Even with this new exposure, however, the US and Europe are unlikely to see huge outbreaks or large numbers of deaths from the dengue virus.

“The story of future changes is really more about large increases in areas that already have dengue, which is going to get a lot worse,” Brady said. He indicated that China and parts of India are particularly at risk. “This is a really scary situation because a large number of people live in these areas and even minor changes could be catastrophic,” he said.

Communities already on the front lines of the climate crisis will always be hardest hit by mosquito-borne diseases, and that’s where investments should be directed, said Shannon LaDeau, a disease ecologist at the Cary Institute for Ecosystem Studies.

But the move of mosquito-borne diseases to regions like the US and Europe is still likely to come as a shock.

“People who live in the temperate zone are going to see their way of life change quite dramatically because they never had to worry about it before,” LaDeau told CNN.

Mosquito eggs float next to a dead mosquito on standing water in a trap placed by the Louisville Metro Department of Health and Wellness on August 25, 2021 in Louisville, Kentucky.

The climate crisis is not entirely positive for mosquitoes. Some places can simply get too hot.

“There’s a certain threshold after which the chemistry in their body just stops working,” LaDeau said. The bad news is that these places can get too hot for humans too.

There are still many unknowns about how mosquitoes will react to the climate crisis. The relationship between climate change and disease is complex, Gossner said.

We know a lot about how temperature changes the ability of mosquitoes to transmit disease, a small amount about how quickly mosquitoes move to new places, and very little about how mosquito populations grow, Carlson said.

Scientists are working to develop tools that can better assess the link between mosquito-borne diseases and climate change.

Meanwhile, there are ways of people they can protect themselves from risksincluding wearing mosquito repellent, placing screens on windows and doors, and getting rid of any standing water in places like pots and gutters.

Scientists are also working on high-tech methods to reduce the population. A project in Florida tried a genetically modified mosquito designed to transmit a lethal gene that kills female mosquitoes – which are the ones that bite.

Other experiments involve using wolbachia bacteriawhich can prevent viruses from replicating inside a mosquito, making them less likely to transmit viruses.

There are also vaccines on the horizon for diseases such as dengue and malaria. “It’s a really big deal,” Carlson said. But whether they will be shared fairly around the world is another question, he added.

“It’s a long way to go in trying to understand how to better use these tools. But there is a lot of hope on the horizon,” Brady said.

Ultimately, tackling climate change will have a huge impact.

The path the world takes to reduce pollution from a warming planet will lead to very different futures for mosquito-borne diseases, Brady said. “Aggressive [climate] mitigation would be by far the least risk.”

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