NORTH COUNTY - For the first time since the potentially deadly West Nile Virus was discovered in local birds three years ago, health officials have reported a definite case of a person who was infected with the mosquito-borne disease in San Diego County.

A 76-year-old man from the El Cajon area has been hospitalized with the disease, which has caused encephalitis, or swelling of his brain, county Health and Human Services Agency officials reported Wednesday afternoon.

The agency did not release much information about his condition. The environmental health director, Gary Erbeck, said in a written statement that officials are searching for mosquito-infested sites around his home, where he liked to garden and sometimes hiked.

West Nile virus is a disease carried by birds and mosquitoes, which transmit the virus to people when they bite. It has infected hundreds of people and thousands of birds throughout California, and health officials have warned since 2003 that the disease would inevitably infect San Diego County residents.

"What this tells us is what we've been saying for a long time," said Jack Miller of the county's health department. "The virus is in the county, and people should protect themselves."

In most patients, the virus does not cause serious illness, but it can cause flulike symptoms -- fever, weakness, headaches -- and serious brain illnesses that can lead to paralysis and death. There have been more than 22,000 documented cases of illness from West Nile virus throughout the United States, and it has killed more than 800 people since its appearance on the East Coast in 1999, according to the Atlanta-based Centers for Disease Control and Prevention. The disease moved west across the country to California, where it has sickened more than 1,875 people and killed 50 since 2002.

In 2004, a San Diego County man was paralyzed by the virus, but the authorities said at the time they could not determine whether he contracted the illness in the county or in the Los Angeles area, where he had recently traveled. Two other cases of the disease were reported in the county in 2003, but officials determined at the time that the virus had been contracted in other parts of the country.

The elderly El Cajon man in the hospital with the virus had not traveled to other counties recently, so authorities determined he was bitten by an infected mosquito somewhere close to home.

Health officials said the appearance of the virus in humans is cause for vigilance, but not panic.

The disease is not spread from person to person, said a deputy public health officer, Wilma Wooten, a doctor with the Health and Human Services Agency. And 80 percent of people bitten by infected mosquitoes do not get sick, she said. Of the 20 percent who do develop West Nile virus symptoms, 1 percent go on to develop severe symptoms, including encephalitis.

"It's possible that there have been cases here that just haven't been reported because the people didn't get sick," Miller said.

Environmental health workers say the best way to prevent West Nile infection is to avoid contact with mosquitoes. Bug repellent and long sleeves are recommended, and the health department has asked that residents eliminate all standing water, in which mosquitoes often breed. The department also has a hot line where residents may report dead birds so that health officials can remove and test the animals for disease.

For more information on the virus or to report mosquito-breeding sites and dead birds, go to www.sdfightthebite.com or call (888) 551-INFO.

- Contact staff write Erin Schultz at (760) 739-6644 or eschultz@nctimes.com.

Steps to protect yourself from West Nile virus

• Eliminate standing water in yards, gardens, children's pools, pots and other

receptacles

• When outdoors, wear long sleeves and pants, and cover exposed skin with

insect repellent containing DEET, Picaridin or oil of lemon eucalyptus.

• Stock ornamental ponds and birdbaths with free mosquito-eating fish from the

county.

• Avoid outdoor activity, especially near water, at dawn and dusk.

• Make sure home screens are tight and free of holes.

• Report mosquito breeding and dead birds to the county at

www.sdfightthebite.com or (888) 551-INFO.

- Source: County of San Diego