LOS ANGELES (CBS) The U.S. is on alert for West Nile virus. It's the most common virus transmitted by mosquitoes, and cases pick up right around this time of the year.
You may have noticed more of those pesky mosquitoes biting recently, and whether they could be carrying West Nile virus is a big health concern now. Thirty-six states are reporting infections in people, birds and mosquitoes.
"We're right now at around the peak period of West Nile virus and this is going to continue into September," said Dr. Peter Hotez of the Baylor College of Medicine. "West Nile virus is the greatest health threat to the United States in terms of mosquito-transmitted viruses."
The CDC says there have been 128 cases of West Nile disease in people in the U.S. this year and four have died.
"One in five individuals will get sick. They'll develop fever, sometimes fever and a rash, and headache. And then a subset of those individuals will progress to what we call neuroinvasive disease, where the virus actually crosses into the central nervous system to cause encephalitis," Hotez said.
Protecting yourself from mosquito bites is critical. The CDC recommends using insect repellent containing one of these ingredients: DEET, Picaridin, IR3535, oil of lemon eucalyptus (OLE), para-methane-diol (PMD) or 2-Undecanone.
Christina McCarthy admits she doesn't always carry bug spray.
"I do have bug spray at home, so maybe I should just move that from my house to my car. This way I have it when we're going on hikes," she said.
Wearing long pants and sleeves can also help keep mosquitoes away. So can limiting time outside during dusk and dawn. People over 60 with underlying conditions such as high blood pressure and diabetes are at higher risk of developing severe illness from West Nile.