As of October 2018[update], the U.S. CDC regarded the cause of AFM as having "a variety of possible causes such as viruses, environmental toxins, and genetic disorders", listing poliovirus, nonpolio enteroviruses, West Nile virus, and adenoviruses among the potential causes.[1][2] More than 90% of people with AFM reported having symptoms consistent with a mild viral infection before the onset of AFM.[11]