West Nile Virus

Source: MedlinePlus Health Topics, U.S. National Library of Medicine

Last synced 8/8/2026Status: primary verified

What is West Nile Virus? West Nile virus (WNV) is an infectious disease. It is most often spread by the bite of an infected mosquito. Most people have no symptoms, while some may develop mild symptoms. But WNV can sometimes cause serious symptoms if the virus enters your brain. How does West Nile Virus spread? WNV usually spreads to people through the bite of an infected mosquito. However, in rare cases, it can spread from person-to-person. This can happen through an organ transplant or blood transfusion . If you are preganant you can spread WNV to your fetus during pregnancy or delivery. And after delivery, it can spread to the baby during breastfeeding . Who is more likely to develop West Nile Virus? Anyone could be bitten by an infected mosquito and get WNV. But certain people are at higher risk for more serious illness they get a WNV infection. They include people who: Are over age 60 Have certain medical conditions, such as cancer, diabetes , high blood pressure , or kidney disease Had an organ transplant What are the symptoms of West Nile Virus? Symptoms can be mild to severe. But most people have no symptoms or mild symptoms. Mild symptoms of WNV can include: Fever Headache Body aches Vomiting Diarrhea Skin rash These symptoms usually go away on their own within a few days to several weeks. But some people will have weakness or fatigue that lasts for weeks or months. Although rare, If West Nile virus enters your brain, it can be life-threatening. It may cause inflammation of the brain ( encephalitis ) or inflammation of the tissue that surrounds the brain and spinal cord ( meningitis ). Serious symptoms of WNV can include: High fever Headache Neck stiffness Numbness Coma Muscle weakness Vision loss How is West Nile Virus diagnosed? To find out if you have WNV, your health care provider: Will do a physical exam Will take your medical history, including asking about your symptoms May order blood tests What are the treatments for West Nile Virus? There are no sp

Educational only

This information is for general education and is not medical advice. Always talk to a licensed U.S. clinician about your situation, medications, or treatment decisions.