Orange County vector control officials on Friday met with residents to teach them how to protect themselves from West Nile virus, which now has nine confirmed human cases in the county.
Nearly every mosquito found in an area of southwest Santa Ana has tested positive for West Nile, authorities said. The human cases are all male, ranging in age from under 18 to 80 years old.
Vector control workers went door-to-door in the neighborhood, handing out flyers and making sure residents are closing their screen doors and using mosquito repellent.
They also warned homeowners about standing water, which could become breeding grounds for mosquitoes.
"We're definitely aware," said resident Jamie Alcarez. "We're trying to take care, trying not to go outside at night."
Alcarez said mosquitoes infected with West Nile were found in traps on his family's property.
Doctors advise people to stay indoors from dusk to dawn, and to wear long sleeves and long pants to keep mosquitoes from biting.
West Nile virus has no cure.
Symptoms include fever, headaches and body rashes, and in severe cases the virus can lead to paralysis or death.
"If you have a fever that has been lasting for several days, that would be a reason to talk to a doctor," said Dr. Matthew Zahn of the Orange County Health Care Agency.
Zahn said one in five people will show symptoms of the virus.
Earlier this year, West Nile virus was confirmed in Hacienda Heights, Diamond Bar, Sherman Oaks and Long Beach.