School Might Be Back, But West Nile Virus Season Isn’t Over

School Might Be Back, But West Nile Virus Season Isn't Over

Published on September 11, 2025

Mosquitoes don't follow the school calendar. While students are back in class, West Nile virus season continues until the first frost-usually in October or November. Here's what you need to know:

What is West Nile virus?

West Nile virus is a mosquito-borne illness that can cause flu-like symptoms in some people and serious neurological illness in rare cases.

When are mosquitoes most active?

Mosquitoes stay active until the first hard frost-often in October or November-so it's important to keep taking precautions even in the fall. West Nile virus cases continue to be reported in Denver right now, so it's more important than ever to protect yourself.

Who is most at risk?

Anyone can get West Nile virus, but adults over 50 and individuals with weakened immune systems are at higher risk for severe illness. People who experience severe illness are at higher risk for hospitalization and death.

How can I protect myself?

Use insect repellent with DEET, picaridin, oil of lemon eucalyptus, or IR3535. Wear long sleeves and pants, especially during dawn and dusk when mosquitoes are most active, or avoid being outside during these times, when possible. Drain standing water around your home to reduce breeding sites.

What are the symptoms?

Most people don't show symptoms. If they do, the most common are fever, headache, body aches, and fatigue. Severe cases may involve confusion, stiff neck, muscle weakness, or other neurological symptoms-seek medical care immediately if these occur.

Even though school is back, West Nile virus season can last well into fall. Mosquitoes stay active until the first frost, often in October or November. Taking small steps-like using repellent and reducing standing water-can help lower your risk.

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