Poliomyelitis is the term used to describe the syndrome of acute flaccid limb weakness and lesions in the grey matter of the spinal cord. Poliomyelitis caused by poliovirus, or polio, rarely occurs in the United States. In 2014, the term AFM was adopted to describe poliomyelitis without a known cause and not caused by poliovirus. AFM has some similarities with polio, such as the lesions in the grey matter of the spinal cord and flaccid limb weakness that can result in paralysis. Polio can be prevented by a vaccine. Stool specimens that we receive from AFM patients are tested for poliovirus. If poliovirus is detected, it is considered a case of polio, not a case of AFM. We continue to test all specimens from AFM patients to look for viruses, including poliovirus and non-polio enteroviruses.