Fresno County health officials said Tuesday a dead crow is the first bird death from West Nile virus this year.
The crow's death is a signal that the virus is present in the area, and health officials reminded people to protect themselves from mosquito bites.
Mosquitoes become infected from biting birds and then pass the virus to humans and horses.
Most people infected with West Nile virus have no or mild, flu-type symptoms, but the disease can cause neurological problems and death.
Last year, there were 372 cases of West Nile virus in California and 14 deaths. There were no deaths in the Valley, but Fresno County reported seven illnesses. Tulare had five illnesses, Madera had three and Kings County had one.
Mosquitoes carrying the virus tend to bite at dawn and dusk.
Health officials also asked people to report any day-biting mosquitoes, which could be Aedes aegypti. The mosquito was first identified in the county last summer and has been detected this spring, the officials said.
The mosquito is not native to California. But last year, it was found in Fresno, Clovis, Madera and Fowler. So far this year, it has been trapped in Clovis and a female Aedes aegypti mosquito was caught in a Madera trap.
No illnesses have been associated with the mosquito so far in counties in the central San Joaquin Valley. There is no indication of disease in the mosquitoes trapped this spring, but they can carry diseases such as dengue, yellow fever and chikungunya.
The Aedes aegypti mosquito is brown with white markings. An aggressive day-biter, it is commonly found in hot, humid tropical areas, like the southeastern United States, Mexico and Central and South America.
More information about mosquitoes and West Nile virus is available at the Fresno County Department of Public Health web site.
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