(Newsroom America) -- A current outbreak of the mosquito-borne West Nile virus is the largest it's ever been in the United States, with more than 1,100 reported cases, the Centers for Disease Control and Prevention in Atlanta said Wednesday.
The total is more than at any time since the disease was first recorded in the U.S. in 1999, the CDC said. Of the 1,118 cases reported thus far, there have been 40 deaths.
"The peak of West Nile virus epidemics usually occurs in mid-August, but it takes a couple of weeks for people to get sick, go to the doctor and get reported," Dr. Lyle Petersen, the director of the CDC's Vector-Borne Infectious Disease Division, told CNN. "Thus we expect many more cases to occur."
He said the reason why so many cases have occurred this year is not clear, but he said unusually warm temperatures may have helped the virus transfer to humans.
Most of the cases - half - have occurred in Texas, with the state confirming 586 outbreaks and 21 deaths. Three-quarters of all the cases are located in Texas, Mississippi, Louisiana, South Dakota and Oklahoma.
While the disease is carried by mosquitoes, CDC officials were quick to note that most mosquitoes do not carry it.
Also, the agency said about 80 percent of those bitten by disease-carrying mosquitoes won't get sick.
Finally, the agency says people over 50 are most vulnerable and most likely to become severely ill by the disease.
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