The first human case this year of West Nile virus in Northern California was reported by Butte County health officials Tuesday.
The virus was identified by a blood donation center while it was performing regular screening on blood samples Friday. The donated blood was discarded, and the person in whose blood the virus was found has been notified, said Lisa Almaguer, a Butte County Public Health Department spokeswoman.
Almaguer said she could not disclose the location of the blood donation center or the city where the human case was found. Statewide, 22 cases of West Nile virus have been reported this year, mostly in Kern, Kings, Los Angeles and San Bernardino counties.
The Butte County Mosquito and Vector Control District said it is not notified of the locations of human cases until people show symptoms, District Manager Matt Ball said.
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Symptoms of West Nile virus include fever, headache, nausea, vomiting and fatigue, according to the U.S. Centers for Disease Control and Prevention. In some cases, the disease can become more serious, causing nerve damage, vision loss, paralysis and death.
To decrease the risk of infection, the vector control district has been setting traps that lure mosquitoes with light and carbon dioxide, and treating standing bodies of water that can be breeding grounds for mosquito larvae. Additionally, mosquitofish, which can eat 200 to 300 mosquito larvae in a day, are being released in unmaintained pools, ponds and rice fields.
If the vector control district is told the location of the human case, it will intensify control efforts in that area by laying more traps, going door to door with education materials and checking backyards for mosquito larvae, Ball said.
To decrease the chance of being bitten by an infected mosquito, health officials recommend draining still water and avoiding contact with mosquitoes by staying indoors around dawn and dusk, dressing in long sleeves and pants and using insect repellant.