West Nile virus found in mosquitoes in three Coachella Valley cities

Mosquitos collected by Chris Horton, of the Berkshire County Mosquito Control Project, are displayed
Rain followed by sudden warm weather this year created temperature conditions perfect for mosquitoes to lay eggs. Mosquitoes transmit West Nile virus to humans.
(Ben Garver / Associated Press)

Four samples of mosquitoes have tested positive for West Nile virus in the Riverside County cities of Coachella, Indio and Thermal, county officials said Friday.

These are the first reports of West Nile in the Coachella Valley this year. While it’s not uncommon for the virus to be found at this time of year, it is atypical to discover a positive finding in three separate areas, officials said.

Rain followed by the sudden warm weather created temperature conditions perfect for mosquitoes to lay eggs.

“There were four times as many mosquitoes in April than we typically see,” said Jill Oviatt, public information manager for the Coachella Valley Mosquito and Vector Control District.


It’s difficult to predict what the findings may mean for the future. Oviatt said it’s possible the recent activity could indicate a high virus season, but it could also taper off. Regardless, the vector control district is doing its best to bring the mosquito populations down.

People should use insect repellent and wear long sleeves and pants, especially at dusk and dawn when mosquitoes are most active. People should also empty any standing water around their homes; those are “perfect breeding grounds” for mosquitoes.

“We live in an area in Southern California where we get very little standing water from rain,” Oviatt said. Instead, much of that standing water comes from the overwatering of lawns and birdbaths, water bowls for pets and dishes under flower pots.

“Just like you take out the trash every week, you should be inspecting your yard,” Oviatt said.


The West Nile virus typically lives in birds and is transmitted to humans and horses from mosquitoes that bite those infected birds. Humans probably won’t know they’ve been bitten by a mosquito carrying the virus unless they develop flu-like symptoms that can result in encephalitis or meningitis. The disease can be fatal in horses. There is an equine vaccine but not one for people.

Last year, there were at least four reported human deaths in California caused by the West Nile virus. In 2017, mosquitoes infected at least 553 Californians, which led to more than 40 deaths.


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