How West Nile Virus Infections Are Treated

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The treatment of a West Nile virus infection depends on the severity of the illness it causes. It can cause a range of clinical syndromes, from a mild flu-like illness (or no symptoms at all) to life-threatening neurological disease with meningitis or encephalitis

Explore what's usually recommended in both scenarios, as well as tips for prevention and more.

Mild West Nile Infections

Most people (8 out of 10) infected with West Nile virus do not develop any symptoms. People who develop a mild case of West Nile fever usually experience some combination of fever, muscle aches, headaches, weakness and fatigue, sore throat, and possibly gastrointestinal problems.

These people usually diagnose themselves with a “bad summer cold,” and treat themselves in the standard ways with rest, fluids, and analgesics.

People with mild West Nile illness usually don't seek medical care and recover fully within a few days.

Serious West Nile Infections

Unfortunately, West Nile virus can also cause much more severe illness, especially if it invades the central nervous system and causes meningitis or encephalitis. People with this form of the infection can experience very high fever, paralysis, confusion, seizures, coma, ​and death.

The treatment of people with serious West Nile virus infections is largely supportive. That is, aggressive measures are taken to bring down the fever, keep up hydration levels, and maintain metabolic and cardiovascular stability—while waiting for the body’s immune responses to finally clear the infection. Such measures may require treatment in an intensive care unit, perhaps for weeks or longer.

Severe West Nile virus infection requires immediate and aggressive medical treatment.

Antiviral medications

Antiviral therapy has not been shown in clinical trials to be of measurable benefit to people with serious West Nile virus infections. However, several of these treatments have been attempted, and there are some anecdotal reports of benefit.

Antiviral agents that have been tried include:

  • Ribavarin: The benefits of this drug against West Nile virus are largely theoretical—it has not even been shown to work in animal models. In one uncontrolled clinical trial during a West Nile outbreak in Israel, the drug was found to be ineffective.
  • Intravenous immunoglobulin: Here again, the potential benefit with intravenous immunoglobulin (IVIG) is theoretical. Making antibodies (immunoglobulin) against West Nile virus is thought to be a chief mechanism by which humans get rid of the virus, so giving IVIG which contains high levels of anti-West Nile antibodies “ought” to work. Unfortunately, the only randomized clinical trial that was conducted to test the effect of IVIG for West Nile virus failed to demonstrate a benefit.
  • Interferon. Interferon seems to be effective against West Nile virus when it is tested in certain animal models. But only a few scattered reports of benefit in patients treated with interferon have been reported; other reports have suggested interferon may be detrimental.

Given this experience with antiviral medication, we can only say that this approach has not been particularly promising.

Supportive care remains the mainstay treatment for West Nile virus infections.

Prevention

The best “treatment” for West Nile virus is prevention. Measures for preventing West Nile virus infections include:

  • Mosquito control programs. Mosquito control programs can be used to eliminate obvious mosquito breeding sites, and larvicidal agents can be sprayed to kill mosquito larvae before they become adults. Such public health measures, when applied strategically, have been shown to substantially limit the incidence of West Nile infection in some communities.
  • Personal protection measures. You should keep your property clear of stagnant pools or puddles that can become breeding grounds for mosquitoes. While outdoors, especially during dusk or dawn when mosquitos tend to be the most active, you should apply insect repellant, and keep as much of your skin covered as possible.
  • Blood donor screening programs. In most developed countries, donated blood products are tested for the presence of West Nile virus before they are transfused. This precaution is thought to have substantially reduced the risk of acquiring West Nile virus from blood transfusions (and that risk was quite low in the first place).

Vaccination

There is no vaccine against West Nile virus for people, though four vaccines have been licensed for horses (which can also become quite ill with West Nile virus). There have been several different approaches to developing a vaccine for humans, and two were evaluated in Phase 2 clinical trials, but they didn't proceed after that, although they were shown to be protective and safe. There is no candidate even close to licensure.

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Article Sources

  1. West Nile Virus. Symptoms, Diagnosis, & Treatment


  2. West Nile Virus. Prevention


  3. Ulbert S. West Nile virus vaccines - current situation and future directions. Hum Vaccin Immunother. 2019;:1-6. doi:10.1080/21645515.2019.1621149

Additional Reading

  • Dayan GH, Bevilacqua J, Coleman D, et al. Phase Ii, Dose Ranging Study Of The Safety And Immunogenicity Of Single Dose West Nile Vaccine In Healthy Adults ≥ 50 Years Of Age. Vaccine 2012; 30:6656.
  • Lothrop HD, Lothrop BB, Gomsi DE, et al. Intensive Early Season Adulticide Applications Decrease Arbovirus Transmission Throughout The Coachella Valley, Riverside County, California. Vector Borne Zoonotic Dis 2008; 8:475.
  • Morrey JD, Day CW, Julander JG, et al. Effect Of Interferon-Alpha And Interferon-Inducers On West Nile Virus In Mouse And Hamster Animal Models. Antivir Chem Chemother 2004; 15:101.