Louisiana and Oklahoma are also hard-hit, with 52 and 49 human cases.
In our area, 5 Pennsylvanians have tested positive, along with one in New Jersey.
Philadelphia Health officials say they're already seeing record numbers for mosquitoes carrying the West Nile Virus.
So today, Action News got a look at what they are doing to help protect people.
"Battery goes in here, close this and leave it overnight," says Bill Ferraro of the Philadelphia Health Department's Vector Control division, as he adjusts a trap.
He and his colleagues have been setting up mosquito traps throughout the city, throughout the summer.
Pools of mosquitoes are caught and sent off to a state lab for testing -
"It lets us know whether they are positive or not," says Ferraro.
So far, the number of mosquitoes positive for West Nile Virus in Philadelphia is the highest its been, thanks to a mild winter and hot summer.
"So the concern is obviously this is coming now into peak season- August and September are peak time for humans to acquire west nile virus," says Ferraro.
Most human cases of the virus are mild, but some can be potentially deadly.
Texas television news producer Katharyn Deville is hospitalized with West Nile meningitis and encephalitis. That means the virus from an infected mosquito has attacked the lining and tissue of her brain.
Even turning a light on a room is almost too much to bear.
"It's this killer, killer headache. It just makes me feel like somebody has an axe in my head and it hurts really bad," Deville says.
Ferraro says the best way to prevent West Nile is to stop mosquitoes from breeding.
That's why Philadelphia and other counties are spraying to kill adult mosquitoes, and Philadelphia is also treating most sewer catch basins to kill larvae.
He says the process is straight-forward, "Pretty much ride around in a vehicle, one drives the other gets out and toss it in."
But Ferraro says area residents also play a big role in the fight against mosquitoes.
They can breed in only a quarter inch of water, such as in a gutter, trash can lid or bird bath.
"So we're always telling people to dump anything that has any kind of water in it," he notes.
If you have questions or concerns about standing water or mosquitoes around your home, call the city's Mosquito Control Hotline - 215-685-9027.
Outside Philadelphia, you can call your county's health department.