SAN DIEGO -- A combination of heat and dead birds prompted county officials Thursday to remind local residents to protect themselves against West Nile virus.

County environmental health officials said 20 new dead birds had tested positive this week for the mosquito-driven disease, and that local residents watering lawns and gardens to battle the recent heat wave could be making themselves vulnerable.

County spokesman Mark Webb said people should be sure to eliminate any standing pools of water -- places where mosquitoes could breed and, eventually, spread West Nile.

"We don't want people getting the disease," Webb said. "This is a reminder to be vigilant. West Nile is here and it's here to stay. Especially during these hot times, people are watering their lawns a lot. There could be buckets out there, green pools where mosquitoes can pop out in five or six days. Dump those buckets, check those drains."

Most people who get infected with West Nile virus don't get sick. But the virus can cause flulike symptoms, and in rare cases, it can cause serious brain swelling and lead to paralysis and death. State health officials report that 10 people have died and 164 people have contracted the disease -- none in San Diego County -- in California this year.

West Nile virus is mainly a bird disease, but it can be transmitted to people and some animals through bites from mosquitoes that have fed on infected birds.

Officials say the best ways to protect yourself from exposure is to wear insect repellant containing the chemical DEET, Picaridin or oil of lemon eucalyptus -- especially around mosquito feeding times of dawn and dusk -- to make sure that windows have tight-fitting screens, and to get rid of any standing water around homes.

Webb said 45 birds have tested positive for the disease in the county so far this year, compared to 19 for all of 2006. Last week, officials reported that a man had become San Diego County's first human West Nile case this year. The man, who lives in Los Angeles, was believed to have contracted the disease there before falling ill in San Diego County.

Contact staff writer Gig Conaughton at (760) 739-6696 or gconaughton@nctimes.com.