Deville in texas. nearly 700 americans have confirmed cases of west nile virus. 26 have died. i ve don t think people need to panic. they need to be aware. reporter: the reason it is so bad is the winter wasn t cold enough to keep them from breeding. it is now a summertime threat. when they bite a little bit, the mosquitoes breed every night, every day. so anyway, yeah, i am concerned. that s why i am bundled up. reporter: overnight in dallas where more than a dozen people have died, they began attacking the virus controversial from the air, something dallas hasn t done since 1966. people that already have lung disease, asthma, hypersensitivity, allergies are more susceptible. reporter: in north carolina, the assault is on the ground with trucks spraying toxic clouds that some worry might be more dangerous than the threat of the virus. experts say the best way to fight the bite is to avoid being outside at dusk and dawn.