What is West Nile Virus?

West Nile virus is caused by a virus that is commonly spread by infected mosquitoes. Mosquitoes get infected after biting infected birds. While West Nile virus is usually found in other parts of the world such as Africa, the Middle East, India and parts of Asia, the virus is present in the United States as well. There are about 1,000 cases of West Nile virus reported in the United States each year. However, these numbers can vary.


Most people infected with West Nile virus do not experience any signs or symptoms. About 20 percent of people experience a mild case of the virus called West Nile fever. The most common signs and symptoms of West Nile fever include fever, headache, body aches, fatigue, back pain, skin rash, swollen lymph glands, or eye pain. These signs and symptoms usually last a few days.

West Nile virus can also be a serious life-threatening condition that causes inflammation of the brain. Less than one percent of people with West Nile virus develop a serious neurological infection. A serious neurological infection may include encephalitis which is inflammation of the brain, or meningoencephalitis which is inflammation of the brain and the surrounding membranes. Some people may also develop meningitis which is inflammation of the membranes surrounding the brain and spinal cord, or West Nile poliomyelitis which is inflammation of the spinal cord, or acute flaccid paralysis, which is a sudden weakness in your arms, legs or breathing muscles. The signs and symptoms of these neurological infections include high fever, severe headache, stiff neck, disorientation or confusion, stupor or coma, tremors or muscle jerking, lack of coordination, convulsions, pain, partial paralysis or sudden muscle weakness.

The risk factors for West Nile virus include:

·         Age: People aged 50 and older having a higher risk of being infected with West Nile virus.

·         Overall health: Having a weak immune system raises your risk for being infected with West Nile virus. People may have a weak immune system after having an organ transplant or having HIV.

·         Geographic location: Cases of West Nile virus have been seen in most parts of the United States. However, the Midwestern and Southern states have the highest incidence rates.

·         Time of year. West Nile virus is most often seen in the United States between the months of July and September.

·         How much time you spend outside: You have a higher risk of being infected with West Nile virus if you work outside or spend a lot of time outdoors.