Health officials on Tuesday urged Los Angelenos to brace for a tough West Nile virus season. (Xinhua Photo) Photo Gallery>>>

    LOS ANGELES, July 15 (Xinhua) -- Health officials on Tuesday urged Los Angelenos to brace for a tough West Nile virus season.

    "The virus is definitely active, and people should be taking precautions," said Susanne Kluh, scientific technical services director for the Greater Los Angeles County Vector Control District (GLAVCD).

    The GLAVCD is the largest of five vector control districts in the county, and covers the city of Los Angeles.

    The Los Angeles County Board of Supervisors is expected to consider a motion by Supervisor Michael Antonovich to direct the departments of Public Health and Public Works to implement planned information and surveillance campaigns and to clear open waterways that could harbor mosquito breeding.

    While cases of West Nile had been on a downswing the past two years, the virus appears to be on the rise again, Kluh said.

    By this time last year, four dead birds and seven mosquito samples had tested positive for the disease in Los Angeles County.So far this year, 41 dead birds and 20 mosquito samples have tested positive, she said.

    There have been no human cases reported in the county thus far. There were none by this time last year either, but ultimately 36 cases were reported in 2007.

    West Nile virus season reaches its peak during August and September, with the last few reported cases trickling in around early October, Kluh said.

    The disease is carried in birds and transmitted through mosquitoes, which bite the birds and spread it to others. Occasionally, those mosquitoes bite humans.

    Most cases in humans go unnoticed or unreported, though the disease hits the elderly and children the hardest, Kluh said. Failure to report infection is especially a problem in Los Angeles County, where so many people are uninsured, she said.

    "People aren't going to see a physician unless they absolutely have to," she said.

    This year's predicated rough season for West Nile can, in part, be attributed to the cyclical nature of the disease, Kluh said. After two fairly light years, there are more birds that have not been exposed to the virus and which lack the antibodies to fight the infection, she said.

    Environmental factors favorable to mosquito breeding also play a role, according to Kluh. With so many foreclosed homes, there are a number of stagnant swimming pools in the county, which make for ideal breeding spots.

    "We're having a huge problem with the home foreclosures," Kluh said.

    West Nile made its debut in the United States in New York City in 1999.

    As its name suggests, it originated in Africa, and was likely brought over via birds, Kluh said.

    It spread westward through migrating birds, striking Los Angeles County for the first time in 2003, and spreading from the Southern California to Northern California. Since then, there have been some 2,320 reported cases of the virus infecting humans, 75 of which were fatal.

    Three cases in humans have been reported in California this year; two in Stanislaus County and one in Tulare County. Of the 380 cases in humans reported statewide last year, three dozen were in Los Angeles County.

    Symptoms of West Nile virus can include fever, body aches, rash, nausea, vomiting and headaches.