Causes

Acute flaccid myelitis might be caused by an infection with a type of virus known as an enterovirus. Respiratory illnesses and fever from enteroviruses are common — especially in children. Most people recover. It's not clear why some people with an enterovirus infection develop acute flaccid myelitis.

In the United States many viruses, including enteroviruses, circulate between August and November. This is when acute flaccid myelitis outbreaks tend to occur.

The symptoms of acute flaccid myelitis can look similar to those of the viral disease polio. But none of the acute flaccid myelitis cases in the United States have been caused by poliovirus.