Mosquitoes collected in Murrieta, Temecula and Hemet tested positive for West Nile virus, officials said Thursday.

The mosquitoes were taken Aug. 11 and 12 and tests by Vector-Borne Disease Section at UC Davis confirmed the insects had the virus, according to a news release from the county Department of Environmental Health.

The mosquitoes were taken from the Monroe Basin area of Murrieta, the northwest corner of Temecula and western Hemet, the release read.

Mosquitoes collected earlier this year in the Coachella Valley also had the virus, said Dottie Merki, program chief for the environmental health department.

Eighty-one mosquitoes in the county were found to be infected last year.

In San Bernardino County, two persons have been infected, public health officials announced last week.

It’s not unusual at this time of year for mosquitoes to have West Nile, officials said.

The virus can be transmitted to humans through mosquito bites. Most people won’t show symptoms but the virus can cause fevers, headaches and body aches. Young children, the elderly and those with weakened immune systems are at greater risk of developing more severe symptoms.