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West Nile Virus Overview
Unlike most diseases which are common to tropical destinations, the West Nile virus has become a reality in our own backyards.
West Nile virus is a type of organism called a flavivirus and is similar to many other mosquito-borne viruses, including Japanese encephalitis. Researchers believe the virus is spread when a mosquito bites an infected bird and then bites a person. A close cousin to St. Louis encephalitis, a virus found in the United States, West Nile can infect humans, birds, mosquitoes, horses, as well as other mammals.
The virus can cause an illness which ranges from mild to severe. The mild, flu-like form is often called West Nile fever. The more severe forms may be called West Nile encephalitis or West Nile meningitis, depending where it spreads.
Affected Areas:
The virus is most commonly found in Africa, West Asia, and the Middle
East. Most recently, it has invaded North America. For more in depth information
regarding the West Nile in North America, please click
here.
How West Nile Virus has Spread
- West Nile virus was first identified in 1937 in the West Nile region of Uganda.
- It was first identified in the US in the summer of 1999 in the Queens borough of New York, NY. It caused 62 cases of encephalitis and 7 deaths that summer.
- Since 1999, the virus has spread throughout the continental US and as of September 2002 has been identified in 42 states.
- The virus has also migrated to Canada, where a handful of people have tested positive for infection.
Mosquitoes carry the highest amounts of virus in early Fall; therefore, there is a peak of disease in late August-early September. The risk of disease then decreases as the weather becomes colder and mosquitoes die off.
Symptoms:
The symptoms for the milder form of the West Nile virus, West Nile fever,
include some or all of the following:
- Fever
- Headache
- Back pain
- Muscle aches
- Lack of appetite
- Sore throat
- Nausea
- Abdominal pain
- Diarrhea
- Swollen lymph glands
- Skin rash
These symptoms usually last for 3 to 6 days.
In more severe cases of the West Nile Virus, the following symptoms can also be seen and require immediate attention:
- Muscle weakness
- Stiff neck
- Confusion
- Loss of consciousness
- Headache
- Fever
- Tremors
- Convulsions
- Paralysis
- Coma
Most people who do become infected with the virus don’t become sick. The estimated 20% who do fall ill, usually only develop the lesser of the two forms of the disease.
Less than 1% of those infected with the virus develop severe infections such as West Nile encephalitis (inflammation of the brain), West Nile meningitis (inflammation of the membrane around the brain and the spinal cord), and West Nile meningoencephalitis (inflammation of the brain and surrounding membrane).
For information regarding prevention of West Nile, please click here.
The types of diseases vary with each destination. After browsing through this site you may also call or email Travel Health Help for more detailed information: 1-888-621-3952
