Heath officials issue warning as 'completely improbable' disease reported in Southwest US: 'It's a very big problem'

Health officials in Arizona are sounding the alarm on how changing weather patterns are affecting the transmission of infectious diseases.

What's happening?

According to AZPM, NPR's Southern Arizona affiliate, scientists are concerned about the relationship between warming global temperatures and mosquito-transmitted diseases. 

The region has seen two confirmed human cases of West Nile virus in 2025

Diseases like West Nile virus are known as "vector-borne diseases," a class of diseases that infect humans through the bites of arthropods like fleas, ticks, and mosquitoes. 

Mosquitoes can not only infect humans, but they can also pick up the disease of an already infected human with their bite.

Why is the relationship between a warmer planet and vector-borne illnesses concerning?

In the American Southwest, rising temperatures mean that summer heat waves are more extreme than ever, which speeds up the mosquito lifecycle, expands their reach and longevity, and increases their numbers. 

Additionally, more intense monsoon seasons are ideal for mosquito breeding, as they need to lay their eggs in water. 

The bug's ability to adapt to changing climate conditions also concerns scientists, as it makes prevention methods a more temporary solution, with the need to update practices over time. 

"The new places that become better for mosquitoes outweigh the places that are currently experiencing and might experience less due to high temperatures," explained Heidi Brown, an infectious disease epidemiologist and professor at the University of Arizona.

In 2021, Pima County in Arizona saw over 100 cases of West Nile virus during a year littered with particularly hot weather and a violent monsoon season. 

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As global temperatures rise and extreme weather becomes stronger, longer, and more frequent as a result, the region will likely see more years of elevated case counts.

"It's one of the things that's fascinating to me as a scientist," Brown said. "These diseases shouldn't exist, right? It just seems completely improbable, and yet it's not. It's a very big problem globally."

What's being done to mitigate disease transmission by mosquitoes?

In Southern Arizona, one of the methods to manage vector-borne diseases is a more indirect approach that addresses other concerns in the area. Municipalities are experimenting with green stormwater infrastructure to recycle much-needed water.

The method not only benefits the water supply but also helps reduce the amount of standing water that makes for ideal mosquito breeding conditions.

"The reason that we care about green stormwater infrastructure is because adding nature back into the urban environment provides all of these benefits in the urban environment that we really need, like cooling, shade, air quality improvement," said Blue Baldwin, program manager for the City of Tucson's climate action initiative Storm to Shade, per AZPM.

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