West Nile Virus

West Nile virus is the leading cause of mosquito-borne disease in the U.S. The virus can infect humans, birds, mosquitoes, horses, and some other animals.

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West Nile Disease FAQs

How is the West Nile virus spread?

A bite from an infected mosquito can spread the West Nile virus. There is no evidence that West Nile virus spreads from animal to person or from person to person except in rare cases through blood product transfusion, tissue transplantation, or mother to baby.

What are the clinical signs and symptoms of West Nile virus infection?

Most people infected with West Nile virus – about 80%- will not develop illness. Twenty percent of infected people develop a typically mild form of the disease (West Nile fever), which may include  fever, headache, body aches, and occasionally a skin rash on the trunk of the body and swollen lymph glands. Only about one out of 150 people infected with West Nile virus will develop the more severe form of the disease (West Nile neuroinvasive disease), which may affect the brain and spinal cord. The signs and symptoms of severe disease may include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. 

The incubation period of West Nile virus in humans is two to 14 days. Signs and symptoms of mild disease may last a few days. Signs and symptoms of severe disease may last several weeks or months, although neurological effects may be permanent. Rarely, death can occur.

How is West Nile virus treated?

There is no specific treatment for West Nile virus infection. 

Is there a vaccine for West Nile virus?

While there is an effective vaccine for horses, there is currently no human vaccine for West Nile virus.  

Is this a seasonal virus?

Though West Nile disease is more common in warmer months, there may be year-round risk of infection in warmer parts of  the state, so protect yourself whenever there is mosquito activity.

How can I reduce my risk of getting West Nile virus?

Preventing mosquito bites is the best way to avoid the West Nile virus. Declare WAR on mosquitoes. 

Information for Specific Groups

Information for Professionals 

West Nile Virus Sample Submission

Additional Resources for Professionals

Texas West Nile Statistics 

Weekly and Annual Arbovirus Statistics

Maps by Year