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Acute Flaccid Myelitis
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Infections

Acute Flaccid Myelitis

Acute flaccid myelitis (AFM) is a rare but serious neurologic condition affecting the spinal cord that causes sudden muscle weakness and loss of reflexes.

What is acute flaccid myelitis (AFM)?

Acute flaccid myelitis (AFM) is a neurologic disease. It is rare, but serious. It affects an area of the spinal cord called gray matter. This can cause the muscles and reflexes in the body to become weak.

Because of these symptoms, some people call AFM a "polio-like" illness. But it is different from polio. AFM is not caused by polioviruses.

What causes acute flaccid myelitis (AFM)?

AFM can be caused by several different viruses. Researchers think that enteroviruses have been causing the recent increases in the number of children with AFM. AFM can also be caused by other viruses, including flaviviruses, herpesviruses, and adenoviruses.

Most people with AFM had a mild respiratory illness or fever (like you would get from a viral infection) before they got AFM.

Who is more likely to develop acute flaccid myelitis (AFM)?

Anyone can get AFM, but most cases (more than 90%) have been in young children.

What are the symptoms of acute flaccid myelitis (AFM)?

Most people with AFM will suddenly have:

  • Arm or leg weakness
  • A loss of muscle tone and reflexes

Some people also have other symptoms, including:

  • Facial drooping/weakness
  • Trouble moving the eyes
  • Drooping eyelids
  • Trouble swallowing
  • Slurred speech
  • Pain in the arms, legs, back, or neck

Sometimes AFM can weaken the muscles that you need for breathing. This can lead to respiratory failure, which is very serious. If you get respiratory failure, you may need to use a ventilator (breathing machine) to help you breathe. If you or your child develops any of these symptoms, get medical care right away.

How is acute flaccid myelitis (AFM) diagnosed?

AFM causes many of the same symptoms as other neurologic diseases, such as transverse myelitis and Guillain-Barre syndrome. This can make it difficult to diagnose. To find out if you have AFM, your doctor may use:

  • A neurologic exam, including looking at where there is weakness, poor muscle tone, and decreased reflexes
  • An MRI to look at the spinal cord and brain
  • Lab tests on the cerebrospinal fluid (the fluid around the brain and spinal cord)
  • Nerve conduction and electromyography (EMG) studies. These tests check nerve speed and the response of muscles to the messages from the nerves.

It is important that the tests are done as soon as possible after the symptoms start.

What are the treatments for acute flaccid myelitis (AFM)?

There is no specific treatment for AFM. A doctor who specializes in treating brain and spinal cord illnesses (neurologist) may recommend treatments for specific symptoms. For example, physical and/or occupational therapy may help with arm or leg weakness. Researchers do not know the long-term outcomes of people who get AFM.

Can acute flaccid myelitis (AFM) be prevented?

There is no specific way to prevent AFM. But you can take steps to prevent getting sick from a virus by:

  • Washing your hands often with soap and water
  • Avoiding touching your face with unwashed hands
  • Avoiding close contact with people who are sick
  • Cleaning and disinfecting surfaces that you frequently touch, including toys
  • Covering coughs and sneezes with a tissue or upper shirt sleeve, not hands
  • Staying home when sick

Frequently Asked Questions

Diagnosis typically involves a combination of clinical evaluation, MRI of the spinal cord to look for gray‑matter lesions, and cerebrospinal fluid analysis. A lumbar puncture and viral PCR testing may identify the underlying virus. In many cases, a definitive diagnosis can be reached within a few days of symptom onset, but it may take longer if imaging or lab results are pending. What treatment options exist for AFM, and can patients expect a full recovery?::There is no proven cure for AFM. Treatment focuses on supportive care, including physical therapy, occupational therapy, and sometimes respiratory support if breathing is affected. Some patients receive antiviral or immunomodulatory therapies, but evidence is limited. Recovery varies; many children regain most or all function over months to years, while others may have lasting weakness. Early rehabilitation improves outcomes. How can I tell if AFM is affecting my breathing, and when should I call emergency services?::Signs of respiratory involvement include rapid or labored breathing, shortness of breath, wheezing, or a sudden drop in oxygen saturation. If you notice any of these symptoms, especially if they worsen quickly, call emergency services right away. Prompt evaluation may prevent respiratory failure and the need for mechanical ventilation. Are there preventive measures or vaccines that can reduce the risk of developing AFM?::Currently, no vaccine specifically targets AFM. Prevention focuses on reducing exposure to viruses that may trigger the condition, such as practicing good hand hygiene, avoiding close contact with sick individuals, and staying up to date on routine childhood vaccinations (e.g., polio, influenza). Research is ongoing to identify specific viral causes and potential preventive strategies.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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