West Nile Virus (WNV) outbreaks are on the rise in all of Southern California, with two deaths in Orange County, more in Los Angeles and a death from the virus this week in San Diego. The virus is spreading at a more rapid pace than expected in the region. The human cases are on the rise this month with the highest totals occurring in Orange County and Los Angeles this week. There were ten and nine reported cases respectively in these counties in the last seven days alone.
California is testing dead birds and the mosquito population: so far the WNV total for dead birds is 1,733 across 34 counties with 39 in Orange County and 79 in Santa Clara County. All the other locations have under 10 birds. L.A. County has reported 20 infections, as of last week. Officials recommend that victims of the virus communicate with others, as most express that they feel no appreciable symptoms. The deaths are more likely to occur in elderly victims of West Nile and those with weakened immune systems face a greater chance of developing severe symptoms, which may require hospitalization.
Orange County has been hit particularly hard with 80 percent of mosquitoes collected testing positive for West Nile Virus. Last year, the positive testers totaled about 10 percent. 90 percent of the dead birds turn in tested positive for WNV. August and September are considered to be the worst two months in the Southland, a fact confirmed by Robert Cummings, ecologist for the O.C. Vector Control District. In a recent press release, the county stated they “lead the state in number of WNV infections this year: 40 to date, compared to fewer than five infections in this time frame for the previous four years.”
Residents have been strongly encouraged to take precautions against contracting the virus, which include using DEET insect repellent or products containing IR3535, avoiding the outdoors from dusk to dawn and wearing long-sleeve shirt and pants when outdoors. Public Health departments also recommend that swimming pools be either cleaned and chlorinated, or drained. They recommend stocking ponds with fish that eat mosquitos and their eggs, particularly goldfish. Finally, officials recommend that all screens be repaired so mosquitos cannot slip into the house.
Most of those in the O.C. who are infected in the current West Nile outbreak are between the ages of 30-50, and all but eight are male. 37 people have the neuro-invasive form of the virus, which can lead to meningitis or blindness. It is believed that WNV is contracted via mosquito bites although it is not yet clear if the original transmission is from birds to mosquitos or vice-versa. However, it has been proven that the virus transfers to humans via a mosquito bite, and that it cannot be transmitted from human to human.
After first being reported in Africa around the time of the Great Depression, WNV was reported in Europe, the Middle East and West Asia in the Fifties. It is believed that the virus entered the U.S. via birds destined for zoo exhibits in 1999. The disease has been reported in birds, horses and humans from Canada to Mexico. The only states without reports of WNV are Alaska and Hawaii.
Many humans who are bitten present no symptoms at all. Many humans display mild symptoms of the virus which can include headache, fever, skin rash and swollen lymph nodes. In severe cases, there may be high fever and meningitis-like symptoms including a stiff neck, disorientation, coma, paralysis and convulsions. The elderly are particularly at risk for the severe symptoms of West Nile, and this population has constituted most of the deaths in the current Southern California outbreaks.
By Jenny Hansen