Three men died last week from complications due to West Nile Virus, bringing Los Angeles County's death toll attributed to the mosquito-transmitted disease to seven so far this year, public health officials announced Monday.
Their deaths indicate that the potentially fatal virus is still being transmitted in October, which is considered late in the season, Dr. Jonathan Fielding, director of the L.A. County Department of Public Health, said in a statement.
"West Nile can appear anywhere in Los Angeles County, or around the state, and we are urging people to take precautions, such as getting rid of pools of stagnant water around their homes and using a repellent containing DEET when outdoors in mosquito-prone areas, especially around dawn or dusk," Fielding said in a statement.
Health officials said two of the men who died were from South Los Angeles, while one was from the San Fernando Valley. All three had pre-existing health conditions and had been hospitalized when they died, according to the statement.
So far, 139 county residents have been diagnosed with West Nile virus.
News of the three new deaths came just as reports surfaced that a mosquito that carries dengue and yellow fever has been found in California's Central Valley.
That mosquito -- Aedes aegypti -- has not been detected in L.A. County, but its close relative the Asian tiger mosquito is present in south El Monte, where officials have tried to keep it under control since its discovery in 2011. On Friday, the San Gabriel Valley Mosquito & Vector Control District sprayed larvacide in southern Arcadia neighborhoods to stop its proliferation.
The presence of disease-carrying mosquitoes in California prove the insects adapt easily, said Kelly Middleton, spokeswoman for the Mosquito & Vector Control District.
"The Asian tiger mosquito naturally exists where it's really humid, but it's been able to adapt to our urban areas in containers," added Levy Sun of the Greater Los Angeles County Vector Control District.
Mosquitoes that carry West Nile have been be more active this year, with 335 infected mosquito pools this year versus 318 in 2012, Sun said.
"We can expect a little more as October goes into November," Sun said. "The warm weather started a lot earlier this year, and that contributed to a higher virus activity."
Last year, six people in L.A. County died of complications attributed to West Nile. Symptoms mimic the flu, including fever, headache and cough. Many people bitten by an infected mosquito have no symptoms, while others develop serious complications.