West Nile virus began to become more than a problem for the U.S. states. Just days ago, Illinois Governor Rod Blagojevich granted more than $2.8 million in funding to health departments all over the state to control mosquito population responsible for spreading the virus.

Now, it is California’s turn to worry about the virus’ spreading, as Orange County authorities reported 13 birds found dead with the virus during the first days of May.

“Thirteen birds in such a short time frame is reminiscent of 2004 conditions” when four people died in the county after becoming infected with the virus, Robert Cummings, Orange County Vector Control science director said as quoted by the Los Angeles Times. That year saw the worst outbreak of West Nile virus in the U.S. with 2,470 people infected and 88 dead, 66 of them in Orange County alone.

The birds including nine crows, two house finches, a hermit thrush, and a black-headed grosbeak were collected between May 1 and May 9 and tested by two separate laboratories, the statement released by the county agency said. The infected birds were found in Brea, San Clemente, Garden Grove, Huntington Beach, Fullerton, Fountain Valley and Anaheim.

Cummings said “the high number of positive birds, the variety of species and the wide distribution is a strong reminder that West Nile virus is present and being actively transmitted in Orange County.”

No human cases have been reported in the county this year.

The infection with the virus starts with one bite from an infected mosquito; for some people this could show no symptoms, while for others could manifest through fever, headaches, chills, weakness, and drowsiness. The most severe cases lead to meningitis or encephalitis, including low levels of consciousness and fatigue.

People are urged to stay away or eliminate any source of water that would benefit mosquitoes. They also must inspect their properties for standing water and remove them. Moreover, they should try to protect themselves the best they can for mosquito bites by using insect repellent and avoiding late night outdoor activities.

The West Nile virus season normally begins in April and lasts until September, but due to warm weather this year, the first cases of the West Nile virus have been reported as early as March 19.