Spring is still three weeks away, but mosquitoes could be buzzing soon if warm weather heats up neglected swimming pools that are backyard hatcheries for the pests.
Mosquito-control officials in the central San Joaquin Valley already are busy fielding complaints.
“When the weather turned warm we started getting calls about swimming pools and people were starting to notice mosquitoes,” said Tim Phillips, manager of the Fresno Mosquito & Vector Control District.
Workers have responded to about 50 calls from homeowners this month, Phillips said. Typically in February “any more than three to four calls a week is unusual,” he said.
The early awakening of mosquitoes also gives Phillips concern. Many could carry West Nile virus, a potentially life-threatening disease that a mosquito can pass to a person in one bite.
Last year, 29 Californians died of neurological complications from the virus and 798 were infected. The Valley had no deaths, but 53 people in Fresno County were infected and 21 were infected in Tulare County. Kings County had five infections and Madera County had one.
Mosquito fighters in the Valley also expect another mosquito to emerge from winter hibernation soon — the Aedes aegypti, a day-biting mosquito that can spread deadly dengue and yellow fevers. The mosquito was first found two years ago in Madera and Clovis, and last year was also found in Tulare County.
So far, none of the A. aegypti mosquitoes trapped in the Valley have been infected with disease and no human infections have occurred, but officials were hoping the winter would be cold enough to kill the mosquito, which is native to tropical climates.
But last winter was mild and so far this one has been too.
It’s also been dry, creating a good environment for West Nile virus.
“Last year, we definitely experienced a bad year for West Nile virus,” said Jodi Holeman, scientific technical services director at the Consolidated Mosquito Abatement District that covers Clovis and other communities in Fresno County.
The Valley drought created perfect conditions for the virus to thrive last spring and summer, Holeman said. And while it’s difficult to predict virus activity year to year, Holeman said this could be another nasty one.
“Certainly during drought years, we see an increase in West Nile virus.”
In a drought, mosquitoes and birds come together at limited water sources, Holeman said. Mosquitoes pick up the virus from biting infected birds and then transmit the virus to humans.
The more time birds and mosquitoes spend together, the more likely mosquitoes will pick up the virus.
With less water in rural ponds and gulleys, they flock to alternative water sources, such as swimming pools in cities, bringing mosquitoes and people together.
“That’s really what we think drives a bad year for West Nile when we have drought conditions,” Holeman said.
David Pierce of Clovis believes an algae-slick swimming pool is likely what brought him into contact last July with a virus-carrying mosquito.
Pierce, 64, was living in a home that was up for sale, and the homeowner had neglected to maintain the swimming pool. Ten days after he moved out, the virus hit: He took a nap and when he awakened, he couldn’t stand. He spent eight days in the hospital.
“The virus caused about 80% paralysis in my body and extreme joint pain. That’s the worst thing I’ve ever been through,” Pierce said. He’s mostly recovered, but continues to have fatigue, he said. “I think all and all it might take a year to get over this completely.”
Pierce said the virus caused encephalitis, an infection of the spinal cord and brain. Only about 1% of people who become infected have severe neurological complications; Pierce said a treatment he had for cancer about a year and a half before the infection may have made him more susceptible. “I guess my immune system was down.”
Before his exposure to West Nile virus, Pierce said he hadn’t given it much thought.
“I just lived in an urban setting. I guess you can get it any time, any place where there’s mosquitoes.”
Now, he shares this advice: “If you see a mosquito, kill that thing.”