Two dead birds found in San Mateo have tested positive for West Nile virus, the San Mateo County Mosquito and Vector Control District announced Tuesday.
A scrub jay was reported Thursday in the Hillsdale area east of Alameda de las Pulgas and an American crow was reported Sunday in the Hayward park area, Mosquito and Vector Control District Vector Ecologist Theresa Shelton said.
They are the county's first cases of West Nile virus this year, according to the district.
As of Friday, 20 cases of West Nile virus had been found in seven counties statewide, which includes one human case in Sacramento County, according to the California Department of Public Health.
The Mosquito and Vector Control District reported five positive cases of West Nile found in birds last year.
Birds are the primary hosts of the virus, which is transmitted by an infected mosquito's bite.
"West Nile virus activity is likely to increase as we head into the summer months," Shelton said.
The district will be putting out mosquito traps in the neighborhoods and testing mosquitoes for West Nile virus in the coming weeks, Shelton said.
Anyone who finds bird or squirrel carcasses is advised to report them to the West Nile virus hotline at (877) 968-2473 or online at www.westnile.ca.gov.