2025 Public Health Laboratory Newsroom
West Nile Virus Cases Continue to Rise in Minnesota – The Public Health Laboratory Responds

Minnesotans are very familiar with mosquitos. Many of us have had those itchy bites, but rarely, do those bites turn into something more serious like a fever, severe headache, vomiting, muscle fatigue, or weakness. After visiting a doctor for these symptoms, you might be surprised to learn that it’s not the flu, but West Nile virus transmitted to you by a mosquito. Minnesota is facing very high numbers of West Nile virus, and the Minnesota Public Health Laboratory is involved in each case severe enough to cause hospitalization.  Read on to learn how scientists at the Public Health Laboratory help monitor West Nile virus across the state.

West Nile virus cases tend to increase in late summer and early fall due to weather conditions and when mosquito populations peak. Minnesota has experienced a very high number of West Nile virus cases in 2025 and according to the Centers for Disease Control and Prevention (CDC), there have been 110 reported symptomatic cases and 2 deaths related to West Nile virus in Minnesota.

Since West Nile virus became a public health concern for Minnesota in 2002, the infectious disease scientists at the Minnesota Public Health Laboratory have been responding to each case by testing samples sent to the lab from symptomatic patients in hospitals. When the lab receives a sample, they use state-of-the-art testing to test for West Nile virus and other mosquito-borne viruses that could be making people sick. A definitive diagnosis of West Nile virus can only be made through laboratory testing.

Through collaborations between the Minnesota Public Health Laboratory, hospitals and clinics across the state, and the CDC, experts at the lab can monitor for increased West Nile virus cases and other, rare mosquito-borne viruses. This allows for a quick response to educate providers and the public, and to work with local mosquito control to decrease activity in affected areas. 

Those most affected by West Nile virus are the elderly, infants, and those who are immunocompromised. Symptoms of West Nile virus include:

• Fever
• Severe headache
• Vomiting
• Muscle aches and weakness
• Sore throat
• Increased fatigue
• And in severe cases, West Nile encephalitis (brain swelling)

If you are experiencing these symptoms, visit a health care professional. Each West Nile virus sample sent to Minnesota Public Health Laboratory helps contribute to data, research, and a better understanding of the health of Minnesotans.

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