Areas of Mountain View were sprayed on Aug. 19 with a mosquito-control pesticide in an attempt to curb the spread of the West Nile virus, which has infected at least five county residents.
Santa Clara County Vector Control “fogged” the area between Highway 237 and Central Expressway to the north; W. Remington Drive to the south; Mathilda Avenue, S. Taaffe Street and Spinosa Drive to the east; and Highway 85 to the west portions of Mountain View and Sunnyvale from 11 p.m. to 2 a.m. Tuesday and Wednesday.
Two of the five county residents infected with the West Nile virus have developed the severe neuroinvasive form that can lead to death, a county spokeswoman said.
The infected residents live where the highest concentration of mosquitoes carrying West Nile were found this year, including Mountain View, Sunnyvale, Santa Clara, Cupertino, Campbell and west and south San Jose, Valley Medical Center spokeswoman Joy Alexiou said.
The cases mark an increase from last year, when two people in the county suffered from West Nile and are the most since the five detected cases in 2006, county officials said.
Three people died from the virus this year in California, but no deaths have ever been reported in Santa Clara County, Alexiou said.
County residents infected with the virus this year live in areas where the county’s vector control district has sprayed the most insecticide to kill the adult mosquitoes this year, she said.
The severe neuroinvasive form that infected two people is called West Nile encephalitis, which attacks the body’s nervous system. One of the other five had West Nile fever symptom and two had the virus but no symptoms, Alexiou said.
Those who run the highest risk of contracting the potentially deadly neuroinvasive form of the virus are the elderly and people with certain chronic conditions, such as diabetes, she said.
The West Nile virus is transmitted to humans and animals by the bites of mosquitoes carrying the virus, but the risk of becoming seriously ill is very low; less than 1 percent of infected people contract encephalitis or meningitis, according to Alexiou.
The county this year has seen an unusually high number of birds that have died from the virus. There have been 648 birds so far, which amounts to half of all birds that reportedly died from the virus in all of California in 2014, Alexiou said.
Of the dead birds found and tested in the county in 2014, 85 percent were infected with West Nile, which means that the risk of humans contacting the virus is higher this year, county officials reported.
The county recommends that people wear long pants and sleeves at night, when mosquitoes are the most active, and use insect repellants when going outside, such as DEET, picaridin, and oil of lemon and eucalyptus.
Residents should also make sure to keep doors and window screens closed to keep the insects out and remove standing pools and containers of water, including pet dishes and birdbaths, where mosquitoes breed, officials said.
— Bay City News Service contributed to this report.
