CDC  (Updated 10/16/18)


A rare, one-in-a-million disease some are calling the “modern polio” has surfaced once again, with the Allegheny County Health Department reporting last week that three local-area children were being treated at UPMC Children’s Hospital of Pittsburgh for suspected acute flaccid myelitis (AFM). The health department neatly summarizes the situation:

Acute Flaccid Myelitis is a rare condition that affects a person’s nervous system, specifically the spinal cord. Since August of 2014, the Centers for Disease Control and Prevention (CDC) has seen an increased number of people across the United States with AFM, with most patients being children. The patients’ symptoms have been most comparable to complications of infection with certain viruses, including poliovirus, non-polio enteroviruses, adenoviruses, and West Nile virus. For most of these cases, the CDC has not been able to confirm a cause. The long-term effects of AFM are also not clear. Some patients diagnosed with AFM have recovered quickly, and some continue to have paralysis and require ongoing care.


AFM occurred sporadically in the United States until 2014, when 120 confirmed cases across 34 states mysteriously appeared. This cluster, which coincided with a nationwide outbreak of a common respiratory virus, EV-D68, got The PediaBlog’s attention four years ago:

Another part of the enterovirus D68 story that’s causing great concern is neurologic: the virus has been associated with extremity weakness and even paralysis in some children.  Other enteroviruses are known to cause rare cases of neurologic conditions, including encephalitis and motor neuron disorders. The children who have presented recently with polio-like flaccid paralysis (polio is an enterovirus) and who tested positive for EV-D68 appear to have had preceding respiratory or gastrointestinal illness.  It’s therefore possible that flaccid paralysis, like other illnesses that occur days or weeks after an initial bacterial or viral infection (rheumatic fever, toxic synovitis, and Guillain-Barré syndrome for example) might be a “post-infectious” immune process that follows infection with EV-D68.


Studying the chart above, one can see that AFM reverted to it’s highly sporadic status in 2015, with only 22 cases reported by the CDC. However, the following year saw another  curious spike — 149 confirmed cases of AFM in 39 states and the District of Columbia — which got our attention once again:

Whatever causes AFM — infectious agent, toxic exposure, or other unexplained phenomenon — leads to the sudden development of profound weakness (to the point of paralysis in some) of arms, legs, and facial muscles. Most affected children need to be hospitalized; involvement of the muscles needed for breathing can result in respiratory failure requiring ventilator support in an intensive care setting. Time to heal and physical therapy are the only options available to cure this mystery disease.


2017 brought another lull in confirmed cases — 33 people in only 16 states. So far in 2018 there have been 38 confirmed cases up to September 30, including six in Minnesota last month.* Children are most commonly affected, reports Kris Mamula:

Boston Children’s has had several cases of suspected AFM in recent months, including one this week, Dr. Benson said. Other outbreaks have been reported in Minnesota and Colorado.

The younger the child affected, the worse the symptoms, which include sudden limb weakness, and loss of muscle tone and reflexes, Dr. Benson said. Treatment is limited to supportive measures such as controlling fever and help with breathing, if needed, and recovery can last a year, with some children left with permanent weakness of the shoulder or legs.


The CDC admits there is still a lot about AFM it doesn’t know yet:

Among the people who were diagnosed with AFM since August 2014:

  • The cause of most of the AFM cases remains unknown.
  • We don’t know what caused the increase in AFM cases starting in 2014.
  • We have not yet determined who is at higher risk for developing AFM, or the reasons why they may be at higher risk.
  • We do not yet know the long-term effects of AFM. We know that some patients diagnosed with AFM have recovered quickly, and some continue to have paralysis and require ongoing care.


Although a non-polio enterovirus and the West Nile virus are two pathogens at the top of the list of suspects causing this very rare condition, the CDC says other viruses, environmental toxins, and genetic disorders should also occupy a space in the clinician’s differential diagnosis. Referring again to the graph above, one hopes that this year’s spike of cases of children with AFM will not be as high as was seen in 2014 and 2016. Finding out the definitive cause(s) of this scary condition will go a long way in easing the public’s mind, especially among those alive today who remember the horrible scourge of poliomyelitis. More about that tomorrow on The PediaBlog.


*Addendum 10/16/18 4:15 PM:  The CDC reports today that there have now been 127 suspected cases of AFM in 22 states so far in 2018. 62 cases have been confirmed. The graph above has been updated to reflect this new data.