March 15, 2005 > West Nile Virus, What Is It? What Can You Do?
West Nile Virus, What Is It? What Can You Do?
by Linda Stone
"This year, Northern and Central California are expected to be the focal points," says John Rusmisel, district manager for the Alameda County Mosquito Abatement District. West Nile Virus, first isolated in Uganda in 1937, is primarily mosquito-borne to humans and has been spreading throughout the United States since first detected in New York City in 1999. Although many people show no symptoms when contracting the virus, some infections can cause influenza-like symptoms, mild skin rash, and swollen lymph nodes and in rare cases, lead to a serious and sometimes fatal inflammation of the brain, called encephalitis.
Infected birds are the primary victim and culprit in the spread of West Nile Virus. Mosquitoes "bite" the birds and are, in turn, infected. From mosquito to humans (and horses) is a short path for the virus. The incubation period for West Nile Virus is five to 15 days, so a person bitten by a mosquito carrying the virus can expect symptoms, if they are to occur, within that period. An estimated one out of 150 people infected will need to be hospitalized.
Rusmisel says that last year, Southern California was the hot spot and since they have had 300 percent of normal rainfall this winter, may end up having another big year. However, outbreaks usually peak in the year after birds are first found with the virus. He adds, "In 2004, Alameda County had 23 birds and five squirrels that tested positive for the virus so we know the virus is here."
So far, eleven counties in California have reported positive tests of birds carrying the virus in 2005. Although there have been no reported cases this year in Alameda County, Rusmisel says recent rains have created breeding pools for Culex tarsalis mosquitos that will begin to emerge in the next few weeks. "When that first crop of mosquitoes emerges, they will amplify the amount of virus in the birds and pass the virus through their eggs to the next batch of mosquitoes."
"We find mosquitoes in many different types of sources; everything from fish ponds, swimming pools, containers, tires, and cemetery flower urns, to creeks, storm water impoundments, tree holes and marshes."
The Alameda County Mosquito Abatement District conducts inspections and treatments throughout the year. "There is some seasonality to some sources so we are able to rotate to the appropriate resources when the time is right." Tree hole mosquitoes are being treated this time of year since after they dry out - around June - they cease to be a problem until the following spring. Rusmisel asks that people help remove backyard sources. "They should dump out any containers that are holding rainwater and change the water in birdbaths and fountains at least weekly."
The district will deliver "mosquito fish" at no charge to residents throughout the County for use in fish ponds, water gardens, horse troughs and unused swimming pools. People who own horses can have them vaccinated for West Nile Virus. Rusmisel adds, "We are asking people to be West Nile Virus NIMBYs (Not in my back yard!)."
The dead bird hot line is 1 877 WNV-Bird or on the web at Westnile.ca.gov. Additional information and requests for mosquito fish is available at www.mosquitoes.org or by calling Alameda County Mosquito Abatement (510) 783-7744.