According to new research from Georgetown University, as many as a billion people could be exposed to mosquitoes carrying tropical diseases by the end of the century. This is, of course, due to global warming caused by climate change.

The research, published in the open-access journal PLOS Neglected Tropical Diseases, was led by Sadie J. Ryan of the University of Florida and Colin J. Carson, Ph.D., a postdoctoral student at Georgetown University’s biology department.

Even if the risk of having a climate suited for mosquitoes is slight, the problem is that the viruses these mosquitoes carry are known for explosive outbreaks of tropical diseases when they show up in the wrong place at the wrong time.

“Climate change is the largest and most comprehensive threat to global health security,” Carlson said. “Mosquitoes are only a part of the challenge, but after the Zika outbreak in Brazil in 2015, we’re especially worried about what comes next.”

According to the World Health Organization, mosquitoes—particularly the species Aedes aegypti and Aedes albopticus—can carry the dengue, chikungunya, and Zika viruses, as well as a number of emerging diseases that researchers say could be a threat in the next 50 years. That makes mosquitoes one of the deadliest animals in the world.

The researchers say almost all of the world’s population could be exposed to mosquito-borne tropical diseases at some point in the next half century. They expect temperature increases to bring year-round transmissions in the tropics and seasonal risks almost everywhere else.

“These diseases, which we think of as strictly tropical, have been showing up already in areas with suitable climates, such as Florida, because humans are very good at moving both bugs and their pathogens around the world,” Ryan explained.

Carlson added, “The risk of disease transmission is a serious problem, even over the next few decades. Places like Europe, North America, and high elevations in the tropics that used to be too cold for the viruses will now face diseases like dengue.”

While Aedes aegypti mosquito populations are projected to explode, the population of Aedes albopticus is expected to seriously decline, most noticeably in southeast Asia and west Africa.

“This might sound like a good news, bad news scenario, but it’s all bad news if we end up in the worst timeline for climate change,” Carlson said. “Any scenario where a region gets too warm to transmit dengue is one where we also have different but equally severe threats in other health sectors.”

The research team analyzed temperatures month by month to project risk through 2050 and 2080. Although the modeling didn’t specify which mosquito would migrate, it did account for a climate where their spread would not be prevented.

“This is only one study to begin understanding the fast-approaching challenges we face with global warming,” Carlson said. “We have a Herculean task ahead. We need to figure out pathogen by pathogen, region by region, when problems will emerge so that we can plan a global response.”

Photo: an Aedes aegypti mosquito on the water. Credit: Shutterstock