SACRAMENTO - Mosquitoes carrying the virus that causes western equine encephalomyelitis (WEE), which can infect and cause disease in the central nervous system, have been detected in Imperial and Riverside counties, State Health Director Diana M. Bontá, R.N., Dr.P.H., announced today. WEE and St. Louis encephalitis (SLE), another virus carried by mosquitoes, have also been detected in a special chicken flock in Imperial County. These viruses are commonly found each summer in California, particularly in Imperial County and other southeast regions of the state.

In most healthy individuals, infection with these viruses produces only mild symptoms, such as headache, fever, fatigue or muscle ache. Severe and potentially fatal illness can occur among infants and the elderly. No human cases of SLE or WEE were reported in 2001.

Each summer throughout California, local mosquito and vector control districts conduct surveillance for mosquitoes and mosquito-borne viruses. Flocks of sentinel chickens are maintained to monitor virus activity in mosquitoes that bite these chickens. Blood samples are obtained from chickens every two weeks and examined by the California Department of Health Services' Viral and Rickettsial Disease Laboratory for evidence of exposure to WEE and SLE. When virus activity is detected, the local districts initiate special efforts to control mosquitoes in the area.

Officials urged Californians, particularly residents who live or work near rural wetlands, to take the following precautions against mosquito bites:

• Avoid activity outside when mosquitoes are most active, especially at dawn and dusk.

• When engaging in outdoor activities, wear long pants, long sleeve shirts and other protective clothing and apply insect repellant according to label instructions.

• Keep infants indoors during peak mosquito hours. If outside, cover cribs, bassinets, or playpens with suspended mosquito netting.

• Identify and eliminate all sources of standing water around your property that can support mosquito breeding.

• Horses also are susceptible to mosquito-borne viruses and should be properly vaccinated.

For more mosquito control ideas or to report unusual mosquito activity, contact your local mosquito and vector control district.

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