A collection of mosquitoes near Polk and Bullard avenues in northwest Fresno has tested positive for Saint Louis encephalitis.
The Fresno mosquito pool is the first to test positive for the virus this year in California, said Tim Phillips, manager of the Fresno Mosquito & Vector Control District. It’s also the first time the city has had mosquitoes test positive for the virus since 1992, Phillips said.
Last year a batch of mosquitoes tested positive for the virus in Fresno County – outside of the city limits. One person became infected, was hospitalized and recovered, Fresno County health officials said. Kern and Sacramento counties each had a Saint Louis encephalitis patient in 2016.
Saint Louis encephalitis virus is transmitted to humans by the bite of infected mosquitoes. The mosquitoes are the same as those that can infect people with West Nile virus.
Most people with Saint Louis encephalitis have no symptoms, according to the federal Centers for Disease Control and Prevention. Those who have symptoms can have fever, headache, nausea, vomiting and fatigue. In severe cases, the person can have neurological problems, often involving encephalitis, an inflammation of the brain. The symptoms usually start abruptly. Older adults are more at risk for severe illness from the virus. The disease can be fatal in rare cases.
Health officials remind people to protect themselves from mosquito bites by using repellent or wearing long sleeves and pants during times of mosquito activity. Also, any standing water around homes where mosquitoes can breed should be eliminated.
To control Saint Louis encephalitis and West Nile virus, mosquito districts will spray insecticides in areas where the insects are infected, said Steve Mulligan, manager of the Consolidated Mosquito Abatement District that covers Clovis. The districts post insecticide “fogging” schedules on their websites, he said.