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    West Nile Virus - Health Topics

    What is West Nile Virus? Where did it come from?

    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.  It was first identified in the United States in August of 1999 in New York State.

    Adult egg-laying mosquito Adult egg-laying mosquito

    How do people get West Nile Virus?

    People become infected with West Nile Virus from the bite of an infected mosquito. Mosquitoes become infected by biting birds which have previously been infected with WNV. There is NO evidence that a person can get the virus from handling infected birds.  West Nile Virus is also not known to be transmitted from person-to-person.

    What are the symptoms of West Nile Virus?

    Most infections are mild. Symptoms may include fever, headache, body aches, skin rashes and swollen lymph glands. When more severe illness occurs, symptoms range from fever, rash and headache to meningitis, encephalitis, coma and, on rare occasions, death.

    Who is at risk for getting West Nile Virus?

    Risk among individuals in the general population is very low. However, people over the age of 50 and those with weak immune systems are at greater risk for more serious illness.

    How is it treated?

    There is no specific treatment for West Nile Virus, nor is there a vaccine. Most people recover completely within two weeks. In more severe infections, intensive supportive therapy may be needed.

    Can birds or other animals get West Nile Virus?

    According to the CDC, West Nile Virus has been detected in over 300 species of birds including crows, blue jays, gulls, ducks, chickens, and hawks.  But only a few species actually show symptoms, and only a few have enough of the virus in their blood to allow mosquitoes that feed on them to become infected.  Of concern are migrating birds, like crows, which can bring the disease to new areas while mosquitoes are still active.

    Many different animals, such as horses, are known to harbor the disease.  According to CDC, approximately 40% of equine WNV cases results in the death of the horse.  But most animals do not show symptoms, or resist infection altogether.  In a limited number of studies on domestic animals, infected dogs showed minimal to no symptoms.

    For more information on WNV in large animals, visit the NJ Department of Agriculture West Nile Virus web page.

    Atlantic County Division of Public Health published this brochure - West Nile Virus in Horses.

    Is There Surveillance for West Nile Virus?

    Yes.  The New Jersey Department of Health and Senior Services (NJDHSS) tests mosquito samples as part of an on-going statewide West Nile Virus surveillance program.  The Atlantic County Office of Mosquito Control also collects mosquito samples that are sent for testing at NJDHSS.  Positive WNV specimens are reported back to the Division of Public Health and this information is disseminated to the municipality.  Public education materials are then distributed to the affected area in addition to a press release to inform residents.  Results are also posted on this website.


    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.

    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.

    Other Websites

    The federal Centers For Disease Control and Prevention has a great deal of information on West Nile Virus.

    The New Jersey Department of Health also provides general information and periodic updates and news releases.

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


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