Reported cases of West Nile virus are climbing higher than usual this year, according to the latest data from the U.S. Centers for Disease Control and Prevention (CDC).
As of Tuesday, 771 infections have been confirmed nationwide—about 40% more than is typical at this point in the year. Historically, most cases are reported in late summer and early fall, peaking in August and September.
Where Cases Are Rising
So far in 2025, infections have been reported in 39 states. The highest numbers—25 cases or more—have occurred in Arizona, California, Colorado, Illinois, Louisiana, Minnesota, North Dakota, South Dakota, and Texas.
West Nile virus has been detected in every state in the contiguous U.S. since it was first identified here in 1999.
What to Know About West Nile Virus
West Nile virus is spread primarily through mosquito bites. Most people infected never develop symptoms. When symptoms do occur, they are usually mild and flu-like, including:
- Fever
- Headache and body aches
- Joint pain
- Rash, vomiting, or diarrhea
These symptoms typically resolve on their own, though fatigue can linger for weeks or months.
In more serious cases, the virus can affect the central nervous system and lead to life-threatening complications. Severe symptoms may include:
- High fever and stiff neck
- Disorientation, tremors, or seizures
- Muscle weakness, paralysis, or vision loss
- Coma in extreme cases
So far this year, the CDC reports 490 “neuroinvasive” cases—those that involve the brain or spinal cord. Recovery from severe illness can take weeks or months, and some effects may be permanent.
No Vaccine, But Prevention Works
There is currently no licensed vaccine or specific treatment for West Nile virus. Infection is believed to provide lasting immunity, but prevention remains the best defense.
The CDC recommends the following steps to reduce your risk:
- Use insect repellent containing DEET, picaridin, or oil of lemon eucalyptus.
- Wear long sleeves and pants when outdoors, especially at dawn and dusk.
- Eliminate standing water around your home where mosquitoes breed.
- Stay indoors during peak mosquito activity when possible.
The Bigger Picture
Since 1999, annual West Nile cases in the U.S. have varied widely—from fewer than 70 in the early years to nearly 10,000 during the 2003 outbreak. Today, the virus remains the leading cause of mosquito-borne disease in the country, averaging about 1,300 cases and 130 deaths each year.
YOU MAY ALSO LIKE
10 Questions Healthy Adults Should Ask About the COVID Vaccine
Can Women with Mental Health Challenges Safely Embrace Motherhood?
Smartwatches May Help Detect PTSD From Media Exposure After Trauma
