Is West Nile Deadly?

  • Medical Author:

    Sandra Gonzalez Gompf, MD, FACP is a U.S. board-certified Infectious Disease subspecialist. Dr. Gompf received a Bachelor of Science from the University of Miami, and a Medical Degree from the University of South Florida. Dr. Gompf completed residency training in Internal Medicine at the University of South Florida followed by subspecialty fellowship training there in Infectious Diseases under the directorship of Dr. John T. Sinnott, IV.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Ask the experts

I saw in the newspaper this week that county health officials have confirmed several cases of West Nile virus in our region. I'm definitely concerned I might contract it, as the mosquitoes this season are really bad. Is West Nile deadly? Can West Nile kill you?

Doctor's response

Since 80% of people who get infected never have any symptoms or signs, the overall prognosis (or likelihood of full recovery) is excellent. Of the 20% who develop symptoms and signs, most are mild and may last for a week, but they may be left with some level of weakness, fatigue, and difficulty concentrating for weeks to months. These residual symptoms are most likely in those over age 50. A questionnaire study of people infected during the 1999 outbreak in New York found that only 37% reported complete return to normal by one year after infection. Interestingly, the likelihood of full recovery does not differ in those who have mild symptoms and signs versus severe disease. Age and overall health before infection is more predictive of an individual's likelihood of recovery. Those over 65 years of age are more likely to be hospitalized, to be discharged to a residence outside the home, and to have prolonged residual effects. Those under 65 years of age are most likely to have full recovery. Children are least likely to be affected by neuroinvasive disease or prolonged residual symptoms and signs.

The following recommendations can help reduce the risk of becoming infected with the virus:

  • Stay indoors at dawn, dusk, and in the early evening.
  • Wear long-sleeved shirts and long pants when outdoors.
  • Apply EPA-registered insect repellent sparingly to exposed skin and clothing according to manufacturer's instructions. An effective repellent contains 20%-30% DEET (N,N-diethyl-meta-toluamide). DEET in high concentrations (greater than 30%) may cause side effects, particularly in children and babies, but it is safe to use in pregnancy. Avoid products containing more than 30% DEET.
  • Picaridin is a newer repellent that is effective and about as long-lasting against mosquitoes as DEET at the same concentrations. It has been used in Europe and has been available in the U.S. since 2005. Unlike DEET, picaridin has no odor, does not damage synthetic fabrics and plastics, and is non-greasy.
  • There are some repellents with essential oils like geranium oil that may be an option for some people, but there is much less data on duration of protection or reliability of protections against mosquitoes. B vitamins are not effective repellents against mosquitoes.
  • Repellents may irritate the eyes and mouth, so avoid applying repellent to the hands of children. Insect repellents should not be applied to very young children (under 3 years of age) or babies.
  • Spray clothing with repellents containing picaridin or DEET since mosquitoes may bite through thin clothing. There are permethrin products that can be applied to clothing that will remain effective through a few washes. For those who work outdoors or need extended protection, permethrin-impregnated clothing is also available.
  • Whenever using an insecticide or insect repellent, be sure to read and follow the manufacturer's directions for use, as printed on the product.
  • Take preventive measures in and around your home. Repair or install door and window screens, use air conditioning, and reduce breeding sites (eliminate standing water).
  • If someone finds a dead bird, the CDC recommends not handling the carcass with bare hands. Contact a local health department for instructions for the notification procedure and disposing of the carcass. After logging a report, they may tell you to dispose of the bird.
  • Note: Vitamin B and "ultrasonic" devices are not effective in preventing mosquito bites.

For more information, read our full medical article on West Nile virus.

For more information, read our full medical article on West Nile virus.



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Reviewed on 9/28/2018