These global changes are only accelerating with global warming, raising fears that mosquito-borne diseases will wreak even greater havoc in the months and years to come.
In June alone, 5 community-acquired malaria cases were found in Texas and Florida. It was the first U.S. case in 20 years. Experts say these cases are unlikely to be related to warmer temperatures, and conditions in Florida and Texas are already favorable for malaria-carrying mosquitoes. However, as urban heat islands expand and temperatures rise, mosquito-borne diseases can be expected to spread outside normal areas.
“Climate change is slowly expanding mosquito ranges,” said Sadie Ryan, a professor of medical geography at the University of Florida.
Earlier this year, researchers at Georgetown University published a paper in Biology Letters demonstrating that the range of malaria mosquitoes in Africa has already shifted from the equator to higher altitudes over the past century.
Malaria cases worldwide have declined steadily for almost two decades. However, progress has stalled in recent years as cases have plateaued or increased in some countries. World Health Organization data show that the number of infected people has risen from a recent low of 231 million in 2018 to an estimated 247 million in 2021.
Mosquitoes don’t kill people like sharks and lions. Rather, mosquitoes are “vectors” for many people. From dengue to malaria to chikungunya, painful and life-threatening diseases. When a mosquito “bites” a person, it sticks its needle-filled proboscis deep into a blood vessel, sucking out blood and leaving behind some of its own saliva.
When that saliva becomes contaminated with viruses and parasites, people get sick, which can often be painful. Dengue fever is also known as “breakbone” fever. The name chikungunya comes from an African word meaning “bend over” because patients often slouch due to severe joint and muscle pain.
And there is reason to think that as temperatures rise, these intolerable and sometimes deadly diseases will spread. Like all insects, mosquitoes are cold-blooded and rely on ambient temperature to maintain body temperature. In particular, it thrives in temperatures between 50 and 95 degrees Fahrenheit. And unlike most humans, which die off in high humidity, mosquitoes love moist air.
In the United States, for example, “mosquito days” are already increasing in many areas as temperatures rise.according to report According to research and communications nonprofit Climate Central, from 1979 to 2022, many parts of the country saw an increase in the number of days when temperatures and humidity were in a sort of “Goldilocks zone” for mosquitoes.
“We’re definitely seeing an extension of the season” for mosquitoes, Ryan explained.
Different temperatures breed different mosquitoes.of Anopheles mosquito Mosquitoes carry malaria.of Aedes aegypti and the Aedes albopictus Mosquitoes carry diseases such as dengue and chikungunya. However, Aedes aegypti grows at higher temperatures than Aedes albopictus. Different regions of the world are warming at different rates, leaving some mosquito-borne diseases prevalent while others are under stress.
according to study Both species are expected to spread north of the United States over the next 30 years, according to a paper published in 2019. By 2050, A. Aedes aegypti It has the potential to extend its range in the Mid-Atlantic and Midwest. Aedes albopictus may reach as far north as Michigan and Minnesota.
There are other factors that are altering disease transmission patterns. As urban areas expand and populations grow, mosquitoes like Aedes aegypti, which prefer to live close to humans, can feed on more habitats and more people. For example, the species is on the rise in Southern California, outraging residents of the area.
Depending on the region, there may be winners and losers in mosquito migration. Many mosquito-borne diseases have an upper limit of ease of transmission. If it gets too hot, diseases like dengue will be less prevalent in the scorching tropics and will instead continue to migrate to the poles.
But Ryan says this doesn’t offer much consolation. “It would not be fun for anyone to live in temperatures that are too hot for dengue to spread,” she says.
