Acute Flaccid Myelitis: 9 Things Parents Should Know

Doctor William C Lloyd Healthgrades Medical Reviewer
Medically Reviewed By William C. Lloyd III, MD, FACS
Written By Jennifer L.W. Fink, RN, BSN on March 2, 2021
  • Female Asian American pediatrician showing tablet to Caucasian mother and son
    Acute Flaccid Myelitis (AFM) 2018 Outbreak: What to Know
    You may not have heard of ‘acute flaccid myelitis,’ but if you’re a parent, you’ve likely heard about the polio-like condition—which can include paralysis—in otherwise healthy children. Some people use the term ‘polio-like virus’ to describe the illness, but researchers do not yet know for sure what causes it. In 2018, an outbreak of acute flaccid myelitis (also called AFM) affected children and families in 40 states. Outbreaks were also reported in the United Kingdom and Canada. Here’s what you need to know about this still relatively rare medical condition and what scientists and healthcare providers are doing about the recent increase in cases.
  • Young African America boy having neck examined by older African American male pediatrician
    1. Acute flaccid myelitis is not new.
    According to the CDC (Centers for Disease Control and Prevention), acute flaccid myelitis is not a new disease. What is new is the increased number of cases, beginning in 2014, when the agency began receiving reports of children paralyzed by what people were describing as a polio-like illness. Between August 2014 and January 2019, the CDC has confirmed more than 520 cases of AFM across the United States. AFM outbreaks have also been reported in the United Kingdom, Canada, and Southeast Asia.
  • Young toddler boy laying on couch on top of sleeping dog
    2. Experts believe a virus triggers AFM.
    Research shows that most AFM patients report a viral-like illness (such as the common cold) with fever about a week before developing AFM symptoms. Scientists have not found poliovirus in anyone with AFM, but they have discovered rhinovirus and non-polio enteroviruses—specifically coxsackievirus and enterovirus D68—in respiratory tract samples from a subset of patients. Other viruses have also been detected. Even though scientists have strong evidence of a viral cause, they can’t explain why some people develop AFM and some do not. Enterovirus infections are very common, so there are other factors yet to be identified that trigger AFM.

    Experts have also noticed that AFM ‘outbreaks’ tend to occur every other year. In 2014, there were at least 120 confirmed U.S. cases; in 2015, there were only 22 cases; 149 cases in 2016; and 35 in 2017. In 2018, there were more than 200 cases.
  • Pediatrician's hands examining abdomen of young Caucasian toddler boy
    3. Anyone can get AFM, but children are most at risk.
    More than 90% of those diagnosed with AFM recently have been children. According to the American Academy of Family Physicians, most affected children have been between the ages of 2 and 8 years. Almost all had a fever or symptoms of a respiratory illness within three days of developing weakness or paralysis of the arms or legs. Healthcare providers don’t know exactly why children are more likely than adults to develop AFM. Despite the recent uptick, AFM is still rare. Your child’s odds of contracting AFM are less than two in a million, according to the CDC.
  • Hispanic mother checking temperature of young daughter on couch with fever
    4. Symptoms of AFM can develop suddenly.
    Many of the children who diagnosed with AFM developed paralysis or muscle weakness overnight. One day, they were fine, aside from mild cold-like symptoms or a fever. The next day, these formerly healthy kids struggled to walk, stand or move their arms. Symptoms of AFM include sudden leg or arm weakness, facial drooping, trouble moving the eyes, difficulty swallowing, and slurred speech. If you notice any of these symptoms, seek immediate medical care.
  • Close-up of two young girls washing hands with soap
    5. You can decrease the chance of infection.
    You may be able to decrease your child’s chances of developing AFM by taking steps to decrease her exposure to common viruses. Practice good hand-washing techniques, and frequently clean and disinfect frequently touched objects, including toys, doorknobs and light switches. Make sure your child’s immunizations are up to date, including the poliovirus vaccine. Although poliovirus has not been detected in people with AFM, unvaccinated people who are exposed to poliovirus are more at risk for developing poliomyelitis, and possibly AFM. You should also take steps to prevent mosquito bites, which can spread West Nile virus, a possible cause of AFM.
  • Young Caucasian boy at exam with middle aged Caucasian female pediatrician
    6. It’s difficult to diagnose AFM.
    The symptoms of acute flaccid myelitis—muscle weakness and paralysis—are common to all sorts of neurologic diseases, including Guillain-Barre syndrome, so it may take time to diagnose AFM. Your healthcare provider will perform a full physical exam and may order an MRI and spinal tap (lumbar puncture, a procedure which involves extracting and analyzing some spinal fluid). The CDC supplied healthcare providers with information on reporting possible cases of AFM (rapid onset of limb weakness or paralysis).

    You can help your provider diagnose the condition by sharing as much information as possible about your child’s symptoms and overall health. Tell your provider about any recent fevers or respiratory symptoms.
  • Nurse's hand holding unseen child patient's hand in hospital
    7. There are no known cures for AFM.
    Doctors treat AFM on a case-by-case basis, using medications and medical treatments to try to improve patients’ symptoms. According to the Genetic and Rare Diseases Information Center, treatments may include antiviral medication, steroids, immunoglobulin replacement therapy, and plasma exchange, but there is no clear evidence these treatments help.

    Healthcare providers who may be involved in AFM treatment include neurologists, infectious disease physicians, and physical and occupational therapists.
  • Young Caucasian boy doing physical therapy leg exercise with African American female therapist
    8. Some patients fully recover; some do not.
    Most patients have persistent muscle weakness even after a year. Early rehabilitation and strengthening exercises may help. Ideally, physical therapists should begin working with people soon after diagnosis. Some physicians have performed nerve transfer surgeries that have helped children afflicted with AFM regain movement. Such surgeries are still rare and are most effective when performed within 8 to 12 months of developing AFM symptoms.
  • Male and female researchers in science lab
    9. The CDC is carefully studying AFM.
    The CDC continues to collect and analyze data about acute flaccid myelitis. The organization has initiated a study at certain pediatric hospitals across the United States in order to learn more about this disease. It’s working with experts to learn more about AFM before 2014; these experts are reviewing old medical records to determine how many cases of AFM occurred before the 2014 outbreak. The CDC has also established a formal AFM task force to uncover the causes of AFM. Knowing the cause will help design effective treatment and prevention programs.
Acute Flaccid Myelitis 2018 Outbreak: CDC Response & States Affected


  1. Ayers T, Lopez A, Lee A, et al. Acute Flaccid Myelitis in the United States: 2015–2017. Pediatrics. 2019;144(5). https://pediatrics.aappublications.org/content/early/2019/10/03/peds.2019-1619
  2. Acute Flaccid Myelitis. Centers for Disease Control and Prevention. https://www.cdc.gov/acute-flaccid-myelitis/index.html
  3. AFM Investigation. Centers for Disease Control and Prevention. https://www.cdc.gov/acute-flaccid-myelitis/afm-surveillance.html
  4. Acute Flaccid Myelitis. MedlinePlus, U.S. National Library of Medicine. https://medlineplus.gov/acuteflaccidmyelitis.html
  5. Acute Flaccid Myelitis in Children. American Academy of Pediatrics. https://www.aap.org/en-us/advocacy-and-policy/aap-health-initiatives/Children-and-Disasters/Pages/Acute-Flaccid-Myelitis-in-Children.aspx
  6. Acute Flaccid Myelitis. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/17991-acute-flaccid-myelitis
  7. Information for Canadians Regarding Acute Flaccid Myelitis (AFM). Government of Canada. https://www.canada.ca/en/public-health/services/diseases/acute-flaccid-myelitis.html
  8. PHE Investigating Rise in Reports of Rare Illness. Public Health England. https://www.gov.uk/government/news/phe-investigating-rise-in-reports-of-rare-illness
  9. Acute Flaccid Myelitis. Genetic and Rare Diseases Information Center. https://rarediseases.info.nih.gov/diseases/13142/acute-flaccid-myelitis
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Last Review Date: 2021 Mar 2
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