The control district decided to launch separate fogging operations after trapping mosquitoes carrying West Nile in sections of Milpitas last Friday and San Jose on Monday, county officials said.
One human case of West Nile has been confirmed in the county so far this year and officials have detected "high levels of the virus" in the county, according to Acting District Manager Russ Parman.
In Milpitas, the area to undergo fogging at about 11 p.m. Wednesday night is bordered by Dixon Landing Road, Washington Drive, West Calaveras Boulevard, the Guadalupe River and Coyote Creek and Interstate Highway 680.
In San Jose, the fogging will start at 11 p.m. Friday in an area bordered by Hostetter Road, Berryessa and La Casa de los Pinos roads, Washington, Salt Lake and Summerdale drives, Gimelli, Viceroy and Foxridge ways and the San Jose Municipal Golf Course.
The West Nile virus is transmitted to humans by mosquito bites and causes mild to severe flu-like symptoms such as fever, head and body aches, and in more serious cases, neurological damage or even death, Parman said.
The virus was first detected in California in 2003 and since then, 3,684 people in the state have come down with it and 134 of them died from it, Parman said.