The first person infected with the West Nile virus in the central San Joaquin Valley this mosquito season lives in Tulare County, the region's epicenter of virus activity.
The Visalia resident was hospitalized but is recovering, county health officials said Wednesday.
The case is the third human infection reported in California this year. In Contra Costa County one person fell ill, and in San Joaquin County one person tested positive for the virus but had no symptoms.
Tulare County mosquito control officials said West Nile virus activity started early and has hit the county hard. So far this year, it has reported more dead birds and infected mosquitoes than any other county in the region.
"There's no rhyme or reason why it will show up in one area more than another," said Yolanda Lourenco, assistant manager and biologist at the Delta Vector Control District in Visalia. But this year, Tulare County appears to be a hotbed for the virus, she said.
As of last Friday, 21 dead birds tested positive for the virus in Tulare County -- surpassed only by Sacramento County with 30 birds and Santa Clara County with 168. Fresno County had three dead birds and Madera had two. Kings and Merced counties reported none, according to the California Department of Public Health.
The number of reported dead birds is higher than usual for this early in the summer, Lourenco said, but hot weather in June probably helped the virus multiply.
Dead birds are a signal that West Nile virus is in a community. Birds carry the virus and mosquitoes become infected when they bite the birds. Infected mosquitoes pass the virus to humans and animals through their bite.
Mosquito control districts capture mosquitoes for testing; Tulare County has had infected mosquito in 40 traps, Lourenco said. By comparison, Fresno County has had six positive samples, she said.
But despite the number of infected mosquitoes, the county has not had a bumper crop of the biting insects this year.
Some areas of the Valley have fewer mosquitoes than in past years, and the drought could be causing the reduction, said Steve Mulligan, director of the Consolidated Mosquito Abatement District in Clovis.
Mosquitoes are concentrating in areas where there is water, Mulligan said: "They're looking for any water they can find." A tire, a bird bath or a plant saucer can be a backyard water source for mosquitoes.
But the biggest backyard breeding grounds are neglected swimming pools. "We're finding an overabundance of mosquitoes in them," Mulligan said.
Most people infected with West Nile will have no symptoms, but a few will develop a fever and other symptoms. Older adults are more at risk of serious illness.
Last year, there were 372 cases of West Nile virus in California and 14 deaths. There were no deaths in the Valley, but Fresno County reported seven patients. Tulare had five patients, Madera had three and Kings County had one.
Mulligan and Lourenco remind people to drain standing water that may produce mosquitoes and to report neglected swimming pools.
They recommend that residents take precautions to avoid being bitten by using mosquito repellent as directed and by dressing in long sleeves and pants at dawn and dusk in areas where mosquitoes are active.
To report mosquitoes and neglected pools
- Fresno County
- Consolidated Mosquito Abatement District: (800) 821-1577
- Fresno Mosquito & Vector Control District: (559) 268-6565
- Kings County
- Kings Mosquito Abatement District: (559) 584-3326
- Madera County
- Madera Mosquito & Vector Control District: (559) 662-8880
- Tulare County
- Delta Vector Control District: (559) 732-8606
- Tulare Mosquito Abatement District: (559) 686-6628
Dead birds and squirrels that may be infected with the West Nile virus can be reported by calling (877) 968-2473 or by filing an online report at the California West Nile website at http://westnile.ca.gov/.
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