Here’s how West Nile is spread — and what symptoms to look for after a mosquito bite
Mosquitoes in San Joaquin and Fresno counties have tested positive for West Nile virus, officials announced Thursday and Friday.
The San Joaquin County Mosquito and Vector Control District found mosquitoes carrying the disease located in zip codes 95366, near Ripon, and 95376, near Tracy. Fresno County’s Consolidated Mosquito Abatement District found mosquitoes carrying the disease located in zip code 93710.
Both reports mark the first of WNV in Northern California this year. The disease has already been found in mosquitoes or dead birds in Orange, Riverside, San Diego and Tulare counties.
Aaron Devencenzi of the San Joaquin County MVCD said the recent uptick of the virus is due to rising summer temperatures, and because mosquitoes thrive in hot weather, the time it takes for them to grow from an egg to an adult shortens.
“So with hot weather like this, we have real fast life cycles, real fast metamorphosis, which increases our whole mosquito populations,” Devencenzi said.
He noted that it is common to see this population boom at this time of year, and it happens every year.
In the Northern California and Central Valley regions, there are dozens of different types of mosquitoes living and breeding. However, two are the primary carriers of the WNV — the Culex tarsalis, a freshwater mosquito, and Culex pipiens, also known as the northern house mosquito.
The northern house mosquito likes to hang around the windows of houses and businesses to get inside, Devencenzi said.
“In the peak of the summer, maybe four to six percent of the species has the virus in them,” he said. “But I don’t want to have people think that if you’re bitten by these species, you’re going to get west Nile virus … And it’s a low percentage, but when you consider billions of mosquitoes, there is a risk.”
The WNV often does not show symptoms. Julie Vaishampayan, the public health director of the Stanislaus County Health Services Agency, said in an email statement to The Modesto Bee that most people — four out of five — who become infected do not have any symptoms.
Vaishampayan added that about one in five infected with WNV will have fever and generally feel unwell with non-specific symptoms like feeling tired and achy. And about one in 100 will develop an infection of the brain, which can be quite serious.
“There is no specific treatment for west Nile and no vaccine,” she said. “The only way to protect yourself is to avoid mosquito bites.”
Some suggestions Vaishampayan gave:
Wear an effective mosquito repellent such as one with DEET, picaridin, oil of lemon eucalyptus, or IR3535.
Avoid being outside at dawn and dusk, when mosquitoes are most active.
Ensure window screens fit tightly and repair tears.
And very importantly, drain all standing water on your property. This is where mosquitoes breed.
For those concerned about standing water or large populations of mosquitoes found on their property, make sure to contact your local mosquito abatement district for further information about mosquito elimination and control.