Most people who contract West Nile virus will never know they had it, as the mosquito-borne illness often produces no symptoms. But some people face a higher threat of life-threatening complications, and a new study has identified who the most at-risk groups are.

What's happening?

For the study, researchers identified risk factors for West Nile neuroinvasive disease, a severe form of the virus that affects the central nervous system, and mortality among American adults with West Nile virus between 2013 and 2024. 

They found that older age, chronic kidney disease, and cerebrovascular disease were significantly associated with West Nile neuroinvasive disease and mortality.

Other risk factors for West Nile neuroinvasive disease include being male, hematologic malignant neoplasms, immunosuppressants, hypertension, alcohol-related disorders, and multiple sclerosis.

Why is this study important?

The authors pointed out that several of the risk factors identified in the study, including age, immunocompromise, hypertension, heart disease, cerebrovascular disease, and chronic kidney disease, are on the rise, indicating that "a growing population in the U.S. may be at risk for morbidity and mortality following [West Nile virus] infection."

Meanwhile, warming global temperatures are creating the perfect storm for more West Nile virus infections in the future, as disease-spreading mosquitoes take advantage of warmer, wetter weather. These warming trends are expected to extend the mosquito season by months in North America, according to The Harvard Gazette. 

Authorities across several states noted some concerning trends in West Nile virus reports in 2025. As of early September, the number of West Nile virus cases across the country was reported to be 40% higher than the norm for that time of year. Later that fall, Missouri health officials reported the highest levels of West Nile virus activity in recent years, and Jefferson County, Kentucky, became another hot spot. 

What's being done about West Nile virus?

According to the Centers for Disease Control and Prevention, the best way to avoid West Nile virus is to avoid getting bitten by mosquitoes.

The agency recommends preventive measures, including wearing long, loose-fitting clothing when outside; using an insect repellent registered with the Environmental Protection Agency; avoiding being outside at dusk and dawn, when mosquitoes are most active; and using screens on windows and doors. 

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