AFM (Acute Flaccid Myelitis) is a rare but serious condition. It affects the nervous system, specifically the spinal cord, which causes the muscles and reflexes in the body to become weak. This condition is not new. However, the large number of AFM cases reported since 2014 is new. The risk of getting AFM varies by age and year. There have been increases in AFM cases every two years since 2014 and mostly in young children. Still, CDC estimates that less than one to two in a million children in the United States will get AFM every year. Anyone can get AFM or neurological conditions similar to it, and there are different causes, such as viruses, toxins, and genetic disorders. There are also no known ways to prevent AFM. The CDC has been thoroughly investigating the AFM cases that have occurred since 2014, when the first large number of cases being reported was noted.
Most patients will have sudden onset of limb weakness and loss of muscle tone and reflexes. Some patients, in addition to the limb weakness, will experience:
Numbness or tingling is rare in patients with AFM, though some patients have pain in their arms or legs. Some patients with AFM may be unable to pass urine. The most severe symptom of AFM is respiratory failure, which can happen when the muscles involved with breathing become weak. This can require urgent ventilator support (breathing machines). If you or your child develops any of these symptoms, you should seek medical care right away.
Certain viruses are known to cause AFM including enteroviruses, such as poliovirus and enterovirus D68 (EV-D68), and West Nile virus. Since 2014, most cases with AFM (more than 90%) had a mild respiratory illness or fever consistent with a viral infection before they developed AFM. Most cases 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 non-polio enteroviruses, and will be temporally associated with AFM. All the stool specimens from AFM cases that the CDC has received to date have tested negative for poliovirus.
Oftentimes, however, despite extensive laboratory testing, a cause for AFM is unable to be identified.
Being up to date on polio shots is one way to protect yourself and your family. Check with your doctor to make sure your family is up to date on all recommended shots. You can protect yourself from mosquito-borne viruses such as West Nile virus—a known cause of acute flaccid myelitis — by using mosquito repellent and staying indoors at dusk and dawn, which is the prime period that mosquitoes bite. Removal of standing or stagnant water from nearby property to minimize the number of mosquitoes is also recommended. To protect yourself and others from non-polio enterovirus infections:
A doctor can tell the difference between AFM and other diseases with a careful examination of the nervous system, looking at the location of the weakness, muscle tone, and reflexes, to help differentiate such patients from patients with other forms of acute flaccid paralysis (AFP). Magnetic resonance imaging (MRI) can be very helpful in diagnosing cases of AFM. Testing nerve response can also be helpful in supporting a diagnosis of AFM; it is important that the tests are performed at the appropriate time (e.g., 7-10 days after onset of weakness) to be helpful. Finally, by testing the cerebrospinal fluid (CSF, the fluid bathing the brain and spinal cord), clinicians can look for findings suggestive of AFM. All of these findings put together help a clinician make a diagnosis of AFM.
There is no specific treatment for acute flaccid myelitis, but a doctor who specializes in treating brain and spinal cord illnesses (neurologist) may recommend certain interventions on a case-by-case basis.