The government says this could be the worst West Nile virus season in history.
Cases of the mosquito-borne virus jumped 60% last week according to the feds.
So far this year, more than 1,100 people have been infected across the United States and 41 have died, including an elderly woman in Fresno County just this week.
Dr. William Schaffner with Vanderbilt Medical School said, "This year looks like the biggest year in years, and we're only starting the major West Nile season."
About one-in-150 patients infected with the virus become seriously ill.