West Nile virus is a mosquito-borne disease that can cause encephalitis, a brain inflammation. West Nile virus was first detected in North America in 1999 in New York, and in Pennsylvania in 2000. Before that, it had only been found in Africa, Eastern Europe, and West Asia.

Infected mosquitoes pass the virus onto birds, animals and people. West Nile virus cases in Pennsylvania occur primarily in the midsummer or early fall, although mosquito season is usually April-October.

QUESTION: What is West Nile encephalitis?

ANSWER: West Nile fever is a case of mild disease in people, characterized by flu-like symptoms. West Nile fever typically lasts only a few days and does not appear to cause any long-term health effects.

More severe disease due to a person being infected with this virus can be West Nile encephalitis, West Nile meningitis or West Nile meningoencephalitis. Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord, and meningoencephalitis refers to inflammation of the brain and the membrane surrounding it.

QUESTION:How can I get it?

ANSWER: The principal way is from the bite of an infected mosquito.

QUESTION: Who is most at risk?

ANSWER: All residents of areas where virus activity has been identified are at risk of getting West Nile encephalitis; persons over 50 years of age have the highest risk of severe disease.

QUESTION: What are the symptoms?

People with mild infections may experience fever, headache, body aches, skin rash and swollen lymph glands. Most people who are infected with the West Nile virus will not have any type of illness. It is estimated that 20 percent of the people who become infected will develop West Nile fever: mild symptoms, including fever, headache, and body aches, occasionally with a skin rash on the trunk of the body and swollen lymph glands.

The symptoms of severe infection (West Nile encephalitis or meningitis) include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. It is estimated that 1 in 150 persons infected with the West Nile virus will develop a more severe form of disease.

Symptoms of mild disease will generally last a few days. Symptoms of severe disease may last several weeks, although neurological effects may be permanent.

QUESTION: Is there treatment or a vaccine?

ANSWER: There is no specific treatment or vaccine for West Nile virus infection. Most people fully recover from the virus. In more severe cases, intensive supportive therapy is needed, often involving hospitalization, intravenous fluids, airway management, respiratory support (ventilator), prevention of secondary infections (pneumonia, urinary tract), and good nursing care.