Condition 101 About West Nile Virus Infection

What is the definition of West Nile Virus Infection?

West Nile virus is a disease spread by mosquitoes. The condition ranges from mild to severe.

What are the alternative names for West Nile Virus Infection?

Encephalitis - West Nile; Meningitis - West Nile

What are the causes for West Nile Virus Infection?

West Nile virus was first identified in 1937 in Uganda in eastern Africa. It was first discovered in the United States in the summer of 1999 in New York. Since then, the virus has spread throughout the US.

Researchers believe West Nile virus is spread when a mosquito bites an infected bird and then bites a person.

Mosquitoes carry the highest amounts of the virus in the early fall, which is why more people get the disease in late August to early September. As the weather becomes colder and mosquitoes die off, there are fewer cases of the disease.

Although many people are bitten by mosquitoes that carry West Nile virus, most do not know they have been infected.

Risk factors for developing a more severe form of West Nile virus include:

  • Conditions that weaken the immune system, such as HIV/AIDS, organ transplants, and recent chemotherapy
  • Older or very young age
  • Pregnancy

West Nile virus may also be spread through blood transfusions and organ transplants. It is possible for an infected mother to spread the virus to her child through breast milk.

What are the symptoms for West Nile Virus Infection?

Symptoms may occur 1 to 14 days after becoming infected. Mild disease, generally called West Nile fever, may cause some or all of the following symptoms:

  • Abdominal pain
  • Fever, headache, and sore throat
  • Lack of appetite
  • Muscle aches
  • Nausea, vomiting, and diarrhea
  • Rash
  • Swollen lymph nodes

These symptoms usually last for 3 to 6 days, but may last a month.

More severe forms of disease are called West Nile encephalitis or West Nile meningitis, depending on what part of the body is affected. The following symptoms can occur, and need prompt attention:

  • Confusion or change in ability to think clearly
  • Loss of consciousness or coma
  • Muscle weakness
  • Stiff neck
  • Weakness of one arm or leg

What are the current treatments for West Nile Virus Infection?

Because this illness is not caused by bacteria, antibiotics do not treat West Nile virus infection. Supportive care may help decrease the risk of developing complications in severe illness.

What is the outlook (prognosis) for West Nile Virus Infection?

People with mild West Nile virus infection do well after treatment.

For those with severe infection, the outlook is more uncertain. West Nile encephalitis or meningitis may lead to brain damage and death. One in ten people with brain inflammation do not survive.

What are the possible complications for West Nile Virus Infection?

Complications from mild West Nile virus infection are very rare.

Complications from severe West Nile virus infection include:

  • Brain damage
  • Permanent muscle weakness (sometimes similar to polio)
  • Death

When should I contact a medical professional for West Nile Virus Infection?

Call your health care provider if you have symptoms of West Nile virus infection, particularly if you may have had contact with mosquitoes. If you are very sick, go to an emergency room.

There is no treatment to avoid getting West Nile virus infection after a mosquito bite. People in good health generally do not develop a serious West Nile infection.

How do I prevent West Nile Virus Infection?

The best way to prevent West Nile virus infection is to avoid mosquito bites:

  • Use mosquito-repellant products containing DEET
  • Wear long sleeves and pants
  • Drain pools of standing water, such as trash bins and plant saucers (mosquitos breed in stagnant water)

Community spraying for mosquitoes may also reduce mosquito breeding.



Centers for Disease Control and Prevention website. West Nile virus. Updated December 10, 2018. Accessed January 7, 2018.

Naides SJ. Arboviruses causing fever and rash syndromes. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 382.

Thomas SJ, Endy TP, Rothman AL, Barrett AD. Flaviviruses (dengue, yellow fever, Japanese encephalitis, West Nile encephalitis, St. Louis encephalitis, tick-borne encephalitis, Kyasanur forest disease, Alkhurma hemorrhagic fever, Zika). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Updated Edition. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 155.

Top Global Doctors For West Nile Virus Infection

Luisa Barzon
Padova, IT
Zdenek Hubalek
Brno, JM, CZ
Koray Ergunay
Ankara, TR

Latest Advances On West Nile Virus Infection

  • Condition: Hyper-Ferritinemia in Patients with COVID-19
  • Journal: Artificial organs
  • Treatment Used: Intravenous Deferoxamine
  • Number of Patients: 0
  • Published —
This article discusses hyperferritinemia (iron oveload) in patients with COVID-19 and its treatment with iron chelation.
  • Condition: Yellow fever, West Nile fever, Japanese and Tick-borne encephalitis, Zika and Dengue
  • Journal: Antiviral research
  • Treatment Used: Remdesivir
  • Number of Patients: 0
  • Published —
The study researched the ability of Remdesivir in treating various illnesses.

Clinical Trials For West Nile Virus Infection

Clinical Trial
  • Status: Recruiting
  • Phase: Phase 2
  • Intervention Type: Drug, Other
  • Participants: 150
  • Start Date: August 11, 2020
Treatment of Covid-19 With Favipiravir Versus Hydroxychloroquine: a Randomized Comparator Trial