West Nile Virus Facts

What is the West Nile Virus? 

The West Nile Virus is an arbovirus that can affect the central nervous system of humans, horses, birds, and other animals. It is spread by mosquitoes. Not every mosquito carries this disease. Infection by the West Nile Virus does not occur between people and animals. Most infections occur in the late summer and early fall. 

Who is at risk for getting severe infection with the West Nile Virus? 

The people at highest risk for getting severe infections, i.e. meningitis or encephalitis, from the West Nile Virus are those over 50 years old and those who are immunocompromised. Infection in children is very rare. 

What are the symptoms of the West Nile Virus infection? 

Most individuals who are infected do not have any symptoms. However, approximately 20% will have mild flu-like symptoms called "West Nile Fever" which consists of fever, headaches, body aches, and possibly swollen lymph nodes. Only a very small percentage, 1%, of those bitten by mosquitoes with the virus get very ill and develop meningitis or encephalitis with high fever, stiff neck, severe headaches, seizures, loss of consciousness, and in particular, muscle weakness. And, of those cases of severe disease, only 3-15% are fatal (meaning only 0.03% to 0.15% of those bitten by infected mosquitoes die from the disease). The incubation period (time from being bitten by the mosquito carrying the disease and symptoms) of the West Nile Virus is about 3-14 days. 

What is the treatment? 

There is no cure for the West Nile Virus. Treatment consists of supportive care including IV fluids, respiratory care, and treatment of secondary infections. 

How do I prevent against this disease? 

The best way to prevent against the West Nile Virus is to prevent being bitten by mosquitoes. For more information on the guidelines for insect repellent, including DEET, please click here . 

What is the "bottom line"? 

The "bottom line" is: the West Nile Virus infection is uncommon, extremely rare in children, and most cases are asymptomatic or mild. 

For more updated information: Click on www.cdc.gov/ncidod/dvbid/westnile/index.htm