What should parents know about West Nile virus?

7 Questions with a Viral Infection Specialist

1. What is West Nile virus and how does it spread?

West Nile is a kind of virus typically transmitted by a mosquito bite. It can affect other animals, including birds like crows and jays. These animals aren’t a risk to people.

2. Is there an outbreak? Where and do we know why?

We are experiencing an increased number of patients who have developed diseases caused by West Nile virus this summer across the country. The total case number in Michigan is the largest reported since the very first year the virus emerged in the US, and Michigan is one of the states with the highest number of cases reported so far this year.  The increased number of cases this year may be at least partly attributed to environmental conditions that allowed for increased numbers and lifespan of the particular type of mosquito that can spread West Nile virus.

3. What are the symptoms of West Nile virus infection?

Most often, there are no symptoms at all. Somewhere around 80% of cases are asymptomatic, meaning people have been infected with the virus but show no sign of infection.

Of the small number of people who do experience effects, most will show symptoms similar to other minor viral infections, including mild fever, body aches or headaches, a brief rash, or nausea and vomiting. Recovery usually takes just a few days for these patients, but symptoms can sometimes last for a week or two.

In rare cases, people suffer from a more severe illness. This is the type of condition we normally see reported in the media. This severe form of disease is seen in less than 1% of people who have contracted West Nile virus infection. For these cases, West Nile virus often affects the nervous system. These cases are known as neuroinvasive disease. Symptoms can include high fevers, severe headache, or neck stiffness. More severe symptoms can include confusion, vision changes, numbness or weakness, seizures, or coma. In contrast to mild symptoms, these severe symptoms can take longer to resolve and may last for several weeks and can lead to permanent effects. Cases of severe neuroinvasive disease caused by West Nile virus can occasionally be fatal.

4. How is the virus treated?

There’s no specific anti-viral drug that can be used to treat West Nile virus infections. For patients experiencing symptoms, care may include supportive treatment like IV fluids and pain medication. Patients with more severe symptoms may need to be hospitalized to receive even more support, such as mechanical ventilation if they are unable to breathe on their own

5. Is there any prevention, treatment or symptoms particular to children parents should know about?

Most children are not at a great risk for infection. Patients older than 50 years of age are probably at greater risk for severe disease caused by West Nile virus infection.  Anybody with a weakened immune system because of illness or medical therapies is also at risk for severe disease.

6. What should a family do to protect themselves from contracting the virus?

Since there is no existing vaccine for West Nile virus that is used in people, the focus is on preventing mosquito bites. The particular mosquito that carries West Nile is most active from dawn until dusk, so don’t wait until sundown to think about prevention.

Use screens on doors and windows, and if possible use air conditioning so you can close entryways. Try to wear long sleeves, pants and socks to avoid bites. Remove breeding grounds for mosquitos by eliminating any standing water near your home. Choose an insect repellent that contains an active ingredient such as DEET or Picaridin. Higher percentages of the active ingredient will provide protection for longer times.

It is important that you are in charge of applying the repellent to your child. Even though the majority of these products are safe for use on children, a child may spray in places that are unsafe. It’s often easiest and safest to apply the repellent to your own hands and then use your hands to put the repellent on your child. Areas to avoid applying on children include the mouth, ears, hands, eyes, open wounds, or irritated skin. Make sure your child changes any clothes that have been sprayed and washes their hands when returning indoors.

The Center for Disease Control’s webpage about West Nile virus and insect repellent is an excellent source for more detailed instructions and recommendations. They also have information available here that details the use of repellent on children.

7. How do we know to seek treatment?

If you think that your child is exhibiting symptoms that could be related to West Nile virus infection, you should see your child’s pediatrician. If your child has severe symptoms, in particular the neurological symptoms discussed above, take your child to an emergency department instead. These symptoms may be related to conditions other than West Nile virus infection, but they are of concern and should be brought to the attention of a medical professional.

Additional Resources:


Jason Weinberg, MD, is an assistant professor of pediatric infectious disease at the University of Michigan.  Dr. Weinberg has held a joint appointment in the Department of Microbiology and Immunology since 2006. When he is not at work, Dr. Weinberg enjoys spending time outside with his family in Ann Arbor. He is an avid cyclist and soccer player.



University of Michigan C.S. Mott Children’s Hospital is consistently ranked one of the best hospitals in the country. It was nationally ranked in all ten pediatric specialties in U.S. News Media Group’s “America’s Best Children’s Hospitals,” including #4 in the country for heart and heart surgery. In December 2011, the hospital opened our new 12-story, state-of-the-art facility offering cutting-edge specialty services for newborns, children and women.