The US Centers for Disease Control and Prevention has confirmed 196 cases of acute flaccid myelitis (AFM), a rare polio-like condition, that causes weakness in the arms or legs, across 39 states in 2018. That number could rise as some cases are still under investigation.
Since 2014, CDC has learned that most of the patients with AFM (more than 90%) had a mild respiratory illness or fever consistent with a viral infection before they developed AFM. Viral infections, such as from enteroviruses are common, especially in children, and most people recover. Investigations into why a small number of people go on to develop AFM, while most others recover, are underway.
The CDC notes the AFM cases are not caused by poliovirus as all stool specimens received from AFM patients have tested negative for poliovirus. The agency has detected coxsackievirus A16, EV-A71, and EV-D68 in the spinal fluid of 4 of 522 confirmed cases of AFM since 2014, which points to the cause of their AFM. For all other patients, no pathogen has been detected in their spinal fluid to confirm a cause.
Most patients had onset of AFM between August and October, with increases in AFM cases every two years since 2014. At this same time of year, many viruses commonly circulate, including enteroviruses, and will be temporally associated with AFM.
Most AFM cases are children (over 90%) and have occurred in 46 states and the District of Columbia since 2014.
In 2018, there were 196 confirmed cases of AFM in 39 states. These 196 confirmed cases are among the total of 357 reports that CDC received of patients under investigation (PUIs). CDC and state and local health departments are still investigating some of these PUIs.
- In 2017, CDC received information for 35 confirmed cases of AFM in 16 states.
- In 2016, CDC received information for 149 confirmed cases of AFM in 39 states and DC.
- In 2015, CDC received information for 22 confirmed cases of AFM in 17 states.
- From August to December 2014, CDC received information for 120 people confirmed cases of AFM in 34 states.
The case counts represent only those cases for which information has been sent to and confirmed by CDC.
What are the symptoms of AFM?
AFM affects a child’s nervous system, specifically their spinal cord. It usually starts with sudden onset of limb weakness and loss of muscle tone and reflexes. Some may also experience:
- facial droop or weakness
- difficulty moving the eyes
- drooping eyelids or
- difficulty with swallowing or slurred speech.
Rare symptoms include numbness or tingling in the limbs and being unable to pass urine. A child may also have difficulty breathing due to muscle weakness that requires ventilator support. Children who experience these symptoms should be seen by a healthcare provider immediately.
Like poliovirus, many of those infected with AFM will fully recover, but a small number will continue to experience limb weakness and/or paralysis and face a lifetime of disability.
For more information on acute flaccid myelitis, visit www.cdc.gov/afm.