Acute flaccid myelitis (AFM) is a rare but serious condition that affects the spinal cord. It can cause sudden weakness in the arms or legs, loss of muscle tone, and loss of reflexes. The condition mainly affects young children.

Most children have a mild respiratory illness or fever caused by a viral infection about one to four weeks before developing symptoms of acute flaccid myelitis.

If you or your child develops symptoms of acute flaccid myelitis, seek immediate medical care. Symptoms can progress rapidly. Hospitalization is needed and sometimes a ventilator is required for breathing support.

Since experts began tracking acute flaccid myelitis following initial clusters in 2014, outbreaks in the United States have occurred in 2016 and 2018. Outbreaks tend to occur between August and November.

The most common signs and symptoms of acute flaccid myelitis include:

• Sudden arm or leg weakness
• Sudden loss of muscle tone
• Sudden loss of reflexes

Other possible signs and symptoms include:

• Difficulty moving the eyes or drooping eyelids
• Facial droop or weakness
• Difficulty with swallowing or slurred speech
• Pain in the arms, legs, neck or back

Uncommon symptoms might include:

• Numbness or tingling
• Inability to pass urine

Severe symptoms involve respiratory failure, due to the muscles involved in breathing becoming weak. It’s also possible to experience life-threatening body temperature changes and blood pressure instability.

If you or your child has any of the signs or symptoms listed above, seek medical care as soon as possible.