Two crows in San Juan Capistrano were found to have West Nile virus this week, the first cases to appear in Orange County.
The discovery did not surprise health officials because the disease has been marching west after making its U.S. appearance in New York in 1999.
A Riverside County man who last week tested positive for the disease is believed to be the first person to acquire the infection in California. He was hospitalized for five days.
The vast majority of people infected with West Nile show no signs of the disease or suffer mild, flu-like symptoms and never know they've had the virus.
The sick crows were reported Oct. 9 by homeowners who noticed the birds didn't fly away when they were approached, said Michael Hearst, spokesman for the Orange County Vector Control District, which combats mosquitoes, rats and other disease-bearing pests. Test results on the birds confirmed Wednesday that they carried the disease.
West Nile is transmitted by mosquitoes that bite an infected bird and pass the virus to another animal, including humans. The disease starts in sparrows and finches before moving to crows, and then to horses and people.
About the same time the crows were brought in, random testing of birds identified an infected finch, Hearst said.
Just because the crows were found near San Juan Creek does not mean the area is especially dangerous, Hearst said, because crows can fly 20 miles a day.
West Nile is common in Africa, East Asia and the Middle East. No vaccine is yet available for humans.