The Control District Santa Clara County Vectors has confirmed the presence of mosquitoes positive for West Nile virus in part of San Jose and Milpitas.
Officials said that, weather permitting, those areas will be treated to reduce adult mosquito populations using truck-mounted equipment on Monday, September 11, beginning around 10 p.m. and ending two to four hours later.
The District's mosquito control program focuses primarily on preventing mosquitoes from reaching the adult biting stage by proactively attacking immature stages of mosquitoes found in standing water.
However, when a mosquito with West Nile virus is detected, the District takes the additional step of performing control treatments on adult mosquitoes.
The District said in a statement that it is critical that adult mosquito control treatments be carried out as quickly as possible upon finding a positive mosquito, as any delay in the request would present an imminent threat to public health and safety, exposing the public to possible vector-borne injuries or even death.
It is noteworthy that treatments to control adult mosquitoes reduce the mosquito population in the area, which decreases the risk of human infection with West Nile Virus.
According to studies, it is normal to see an increase in West Nile virus during the summer and early fall because mosquitoes thrive in warm climates.
Given this, the District said it has a surveillance program dedicated to detecting the presence of diseases such as West Nile virus, St. Louis encephalitis and Western equine encephalitis, all of which are transmitted by the bite of infected mosquitoes.
The data collected through surveillance is used to predict locations most likely to have these disease-carrying mosquitoes.
The District said it has been regularly conducting truck-mounted adult mosquito control treatments since 2003 to successfully reduce populations of mosquitoes that transmit West Nile virus.
The Vector Control District stressed that it is not necessary to relocate during the treatment to control adult mosquitoes, as they represent a minimal risk to people, pets, animals and the environment when applied by an authorized professional.
However, he said, those who wish to take extra precautions can keep their family members and pets inside during the roughly four-hour mosquito control treatment, with windows and doors closed.
In the morning, the pesticide breaks down quickly when exposed to sunlight. Since the District applies pesticides in ultra-low volume, people are unlikely to breathe or touch anything that has enough pesticide on it to be harmful.
Since West Nile virus arrived in California in 2003, more than 7,000 people across the state have contracted the disease; nearly 400 of those cases were fatal. In 2022, there have been 15 human deaths related to West Nile virus; 2015 was a record year for deaths in the state with 55 deaths.
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