West Nile virus activity has started earlier than usual, with the highest number of reported cases by the end of June since 2004.
Most people who become infected never develop symptoms, but early recognition of illness can help people seek medical care if symptoms appear.
Simple steps like using insect repellent, wearing protective clothing, and avoiding peak mosquito hours can lower your risk all summer long.
Summer means more time outside, but it also means mosquito season is in full swing.
This year, the Centers for Disease Control and Prevention (CDC) says West Nile virus activity has gotten off to an unusually early start. By June 30, 2026, the agency had received reports of 48 human cases, including 38 cases involving severe neurologic disease. That's the highest number of reported infections at this point in the year since 2004.
The virus has already been detected in 23 states, making this the widest early-season activity seen in the past decade. While many people enjoy spending time outdoors throughout the summer, health officials say it's a good reminder that mosquito bite prevention should remain part of warm-weather routines.
"These findings serve as an important reminder that mosquito season is well underway," CDC Medical Epidemiologist Dr. Erin Staples said in a news release.
Why early detection and ongoing prevention matter
One challenge with West Nile virus is that most infected people never develop symptoms. However, about one in five people experience fever along with symptoms such as headache, body aches, joint pain, vomiting, diarrhea, or a rash.
In fewer than 1% of infections, the virus can cause serious neurologic illnesses, including meningitis or encephalitis, which may lead to long-term disability or death.
Adults ages 60 and older, along with people who have certain underlying medical conditions, face a greater risk of severe illness. That's why recognizing symptoms if you become sick during mosquito season — and continuing to prevent mosquito bites throughout the summer — is so important.
The CDC also notes that prevention doesn't stop with individuals. State and local health departments continue monitoring mosquito populations and carrying out mosquito control efforts where appropriate, while the CDC works with public health partners across the country to track disease activity and provide guidance.
How to reduce your risk this summer
Use an Environmental Protection Agency (EPA)-registered insect repellent whenever you're outdoors.
Wear long, loose-fitting shirts and pants to make it harder for mosquitoes to bite.
Limit outdoor activities between dusk and dawn, when the mosquitoes that spread West Nile virus are most active.
Keep mosquitoes out by using window and door screens or air conditioning when available.