States from California to the Carolinas have reported cases, with Texas hit hardest.
Nearly half of the reported 1,100 West Nile cases nationwide have occurred in Texas.
Dallas County has launched an extensive West Nile education campaign, even stopping cars to hand out flyers with prevention information.
The vast majority of people who get the mosquito-borne disease don't actually get sick, but so far more than 600 people have developed a severe neuro-invasive form of West Nile which can include meningitis and swelling of the brain.
At least 41 people have died.
Experts say even those who survive can have long-term problems.
They recommend eliminating standing water from around your home, where mosquitos breed.
Insect repellants and clothing that covers the arms and legs are also recommended.
Those who track West Nile cases at the Centers for Disease Control and Prevention project this could be the worst year for west nile since it first appeared in the U.S. In 1999.