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Acute Flaccid Myelitis in U.S. Children

Frustrated mother holding baby

CDC continues to receive reports of children with acute flaccid myelitis (AFM), a rare but serious condition. CDC is working hard to find the causes of these AFM cases. Learn more about AFM and symptoms that require immediate medical care.

Parents may be hearing about children in the United States who suddenly became weak in their arms or legs from a condition called acute flaccid myelitis, or AFM. This condition is not new, but the large number of reports we have received since 2014, when we first started our surveillance for this condition, is new. AFM affects the nervous system, specifically the spinal cord, which can cause the muscles and reflexes in the body not to work normally.

What CDC has learned since 2014

  • Most of the patients with AFM (more than 90%) had a mild respiratory illness or fever consistent with a viral infection before they developed AFM.
    • Viral infections such as from enteroviruses are common, especially in children, and most people recover. We don’t know why a small number of people develop AFM, while most others recover. We are continuing to investigate this.
  • These AFM cases are not caused by poliovirus; all the stool specimens from AFM patients that we received tested negative for poliovirus.
  • We detected coxsackievirus A16, enterovirus A71 (EV-A71), and enterovirus D68 (EV-D68) in the spinal fluid of four of 484 confirmed cases of AFM since 2014, which points to the cause of their AFM. For all other patients, no pathogen (germ) has been detected in their spinal fluid to confirm a cause.
  • Most patients had onset of AFM between August and October, with increases in AFM cases every two years since 2014. At this same time of year, many viruses commonly circulate, including enteroviruses, and will be temporally associated with AFM.
  • Most AFM cases are children (over 90%) and have occurred in 46 states and DC.

Learn more about CDC’s investigation of AFM.

In 2014, CDC got a large number of reports of people, mostly children, with AFM. Since then, we’ve been working hard to better understand AFM, what puts people at risk of getting it, and the possible causes. AFM remains rare (less than one to two in a million people), even with the recent increase in cases. However, AFM is serious, and we don’t yet know what causes most people to get it or how to protect people from getting AFM. As we continue to learn about AFM, we urge parents to seek medical care right away if their child develops symptoms of AFM.

Mother teaching her child how to wash hands

While we don’t know if effective in preventing AFM, washing your hands often is one of the best ways to avoid getting sick and spreading germs to other people.

Symptoms of AFM

AFM is rare, but it can lead to serious neurologic problems. You should seek medical care right away if you or your child develops any of these symptoms:

  • weakness and loss of muscle tone and reflexes in the arms or legs
  • facial droop or weakness
  • difficulty moving the eyes
  • drooping eyelids
  • difficulty swallowing
  • slurred speech

Infections That Can Cause Conditions like AFM

Certain viruses, such as poliovirusenterovirus A71, and West Nile virus, can cause AFM. You can protect yourself and your children from these viruses by:

  • Making sure you are all up to date on polio vaccinations.
  • Protecting against bites from mosquitoes, which can carry West Nile virus, by using mosquito repellent, staying indoors at dusk and dawn (when bites are more common), and removing standing or stagnant water near your home (where mosquitoes can breed).
  • You can protect yourself and others from enteroviruses by washing your hands often with soap and water, avoiding close contact with people who are sick, and cleaning and disinfecting frequently touched surfaces, including toys.

What CDC Is Doing About AFM

CDC has been investigating AFM ever since we got a large number of reports of this condition in August 2014.

AFM is a complex condition. We have done extensive lab testing on specimens from patients, but have not determined what caused most of these people to get AFM. It is unclear what pathogen (germ) or immune response caused the arm or leg weakness and paralysis. There could also be something else triggering the patient’s AFM, such as a genetic factor that may make them more susceptible.

We are continuing to learn as much as we can about AFM by looking at each case to find possible causes of this condition, and determine why some people go from having a mild respiratory illness or fever to developing AFM.

Also, we are working with health departments to educate doctors in every state so they are aware of the symptoms of AFM, and will provide reports of patients they suspect may have AFM to their health departments as soon as possible. Some educational activities and materials include health alerts, job aids, toolkits, webinars, and scientific publications and presentations. For more information, see AFM references and resources.

If you would like to learn more about what CDC is doing, please visit CDC’s AFM Investigation webpage.

If you would like to learn more about AFM, please visit CDC’s AFM website.

For general questions about AFM, please email us at