(CNN) — The recent West Nile virus outbreak is the largest ever seen in the United States, according to new numbers from the Centers for Disease Control and Prevention.
The number of cases so far this year is the highest recorded through August since the disease was first detected in the United States in 1999. As of August 21, 38 states had reported human infections. The cases reported to the CDC total 1,118, including 41 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,” said Dr. Lyle Petersen, the director of the CDC’s Vector-Borne Infectious Disease Division. “Thus we expect many more cases to occur.”
Petersen said that the reason for the high number of cases this year is unclear, but that unusually warm weather could have fostered favorable conditions for the disease’s transfer to humans.
About 75% of the cases are in Texas, Mississippi, Louisiana, South Dakota and Oklahoma. Texas has been at the epicenter of the outbreak, with 586 confirmed cases and 21 deaths, according to the Texas Department of State Health Services.
