WHAT IS WEST NILE VIRUS?

West Nile Virus (WNV) is a mosquito-borne virus. As its name implies, WNV is typically found in Africa, Europe, and Asia. Infection with this virus does not always result in human disease. Studies have shown that only a small percentage of humans infected with the virus will show symptoms of the disease. The general symptoms of West Nile fever, resulting from infection with WNV, range from fever, headache, and rash to meningitis, encephalitis, coma, and death.

CARRIERS OF WEST NILE VIRUS

West Nile Virus is transmitted primarily through the bite of an infected mosquito. In the United States, the common house mosquito (Culex pipiens) is considered to be the primary carrier of WNV.

Culex pipiens is the principal mosquito species found in urban and suburban environments. The larvae are commonly found in polluted water collecting in roadside ditches, catch basins, artificial containers such as tires, and in unused swimming pools. Although Culex pipiens prefer to feed on bird hosts, these mosquitoes will readily bite humans and other mammals.

WEST NILE VIRUS TRANSMISSION CYCLE

The virus has a life cycle in which the mosquito is infected while feeding on blood from an infected bird, or in rare cases, an infected mammal. The mosquito may then infect other birds or mammals while taking another bloodmeal. However, WNV has not been shown to be transmitted directly from birds to people or other animals; likewise, person-to-person infections are not possible.

WEST NILE VIRUS IN HUMANS

When people become infected with WNV, a flu-like illness often follows. In humans, the virus has an incubation period of three to 10 days. Therefore, symptoms may appear suddenly and are often characterized by high fever, headache, backache, fatigue, and nausea. There is no known treatment for persons infected with WNV, nor is there a vaccine. Most people recover from infection completely within two weeks.

However, 10 - 15 % of cases result in fatalities. Most fatal cases occur in people greater than 50 years of age. Infected persons cannot pass the virus back to uninfected mosquitoes.

WNV IN BIRDS AND OTHER ANIMALS

Although many species of birds can be infected with the virus, crows, gulls, ducks, chickens, hawks, and pigeons are known to show symptoms. Of concern are migrating birds, like crows, which can bring the disease to new areas while mosquitoes are still active. Crows tested for WNV in the northeastern U.S. in 1999 showed a very high fatality rate.

Among other animals, only horses, sheep, mice, hamsters, and lemurs are known to show symptoms. Many different animals, even frogs, are known to harbor the disease. A few of them act as reservoirs of the disease, meaning that they have enough of the virus in their blood to allow mosquitoes to become infected. But most animals do not show symptoms, or resist infection altogether.

For more information on WNV in large animals, CLICK HERE for information from the New Jersey Dept. of Agriculture.

WEST NILE VIRUS IN AMERICA

In 1999, there were 63 confirmed cases of West Nile virus in the U.S., and seven deaths, all from New York State. These are the first recorded cases of WNV in North America. It is not known how common West Nile virus is or will become in the U.S. In Europe, WNV has caused sporadic human cases and outbreaks in irregular intervals.

OTHER WEBSITES

The federal Centers For Disease Control and Prevention has a great deal of information on West Nile Virus. www.cdc.gov/ then go to "Health Topics A-Z", "In The News" or "EID Journal"

The New Jersey State Department of Health and Senior Services also provides general information and periodic updates and news releases. www.state.nj.us/health/ then go to "Topics A-Z" or "In the Spotlight - West Nile Virus Update"

Visit the Atlantic County Mosquito Control Unit for more specific information on mosquitoes and mosquito control in Atlantic County!