Health Topic

West Nile Virus

West Nile Virus (WNV) is a virus spread by mosquito bites. Most people have few to no symptoms. But some have severe symptoms. Learn about prevention and treatment.

Reviewed Reviewed by a registered pharmacistGeneral information

Also called: WNV

Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.

About 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.

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.

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

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

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

There are no specific vaccines or treatments for human WNV disease. But rest, fluids, and over-the-counter pain medicines may relieve some symptoms. You may need to be hospitalized if you have serious symptoms.

There are no vaccines or medicines to prevent WNV. The best way to avoid WNV is to help prevent mosquito bites:

  • Wear insect repellent with DEET or another U.S. Environmental Protection Agency (EPA)-registered insect repellent. Make sure to follow the instructions for using the repellent.
  • Wear long-sleeved shirts and pants if you're outside.
  • Get rid of mosquito breeding sites by emptying standing water from flowerpots, buckets, or barrels.
  • Stay indoors between dusk and dawn, when mosquitoes are most active.
  • Use screens on windows to keep mosquitoes out.

Centers for Disease Control and Prevention (CDC)

It sits within Infections and Brain and Nerves.

The lead U.S. institute for this subject is the National Institute of Allergy and Infectious Diseases.

When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.

Research on West Nile Virus

27 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.

What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.

Research currently under way

Research already completed

Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.

Where to read more

Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.

Start Here

Symptoms

Prevention and Risk Factors

Related Issues

Statistics and Research

Clinical Trials

Medical subject headings

Clinicians and researchers index this subject under West Nile Fever. These are the terms to use when searching medical literature.

This page is built from the MedlinePlus health topic record for West Nile Virus, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.