The first human West Nile Virus infection in Orange County this season reported

A Buena Park woman was diagnosed last week with West Nile Virus (WNV) infection, and was hospitalized but is recovering. This is the first human WNV infection identified in Orange County this season. As of Friday, the California Department of Public Health has reported 46 cases of human West Nile Virus infections statewide this season, including three in Los Angeles County.

West Nile virus (WNV) is the leading cause of mosquito-borne disease in the continental United States.  It is most commonly spread to people by the bite of an infected mosquito. Cases of WNV occur during mosquito season, which starts in the summer and continues through fall. There are no vaccines to prevent or medications to treat WNV in people. Fortunately, most people infected with WNV do not feel sick. About 1 in 5 people who are infected develop a fever and other symptoms. About 1 out of 150 infected people develop a serious, sometimes fatal, illness. 

The incubation period is usually 2 to 6 days after a bite from an infected mosquito. Most symptomatic WNV cases have an acute febrile illness. Symptoms also include headache, malaise, arthralgia, or myalgia, and occasionally nausea, vomiting and/or a maculopapular rash. About 1 in 150 WNV-infected persons develops neuroinvasive disease, which can manifest as encephalitis, aseptic meningitis, acute flaccid paralysis, and/or transverse myelitis.

Testing for WNV: Testing for WNV should include serum WNV IgM and IgG, with CSF IgM when a lumbar puncture is performed. Because serum WNV IgM may be negative early in the course of disease, repeat serology may be indicated if initial testing was done within 8 days after the onset of illness.

Health care providers should consider WNV infection in patients with prolonged fever or acute neurologic illness.

Surveillance of West Nile Virus in the community: Report all WNV infections to Orange County Public Health by phone (714-834-8180) or fax (714-564-4050) within 1 working day. For more information on mosquito surveillance and control activities, please visit the Orange County Mosquito and Vector Control District website at http://www.ocvector.org/.

• Avoiding mosquito bites is the best way to prevent WNV infection:
• Eliminate standing water which can serve as mosquito breeding sites around the home or workplace.
• Ensure windows and door screens are in good repair.
• Use an insect repellent containing active ingredients registered with the U.S. Environmental Protection Agency when outdoors. Active ingredients include DEET, picaridin, and oil of lemon eucalyptus. Natural bug sprays may not be effective against mosquitoes. For more information, visit http://www.cdc.gov/westnile/faq/repellent.html.