Acute Flaccid Myelitis (or AFM) is a paralyzing condition that looks similar to Polio and tends to peak every other year. The last surge of cases was in 2018, when 238 cases were diagnosed across the U.S. The CDC believes that we will see another surge this year.
Though AFM can occur at any age, the average age of incidence is 5 and the most common symptoms are weakness, difficulty walking, pain in the neck, back, or a limb, and fever. Most patients had a fever and/or respiratory illness for a few days before they started showing the muscle weakness that is the most telling symptom of AFM.
In 2018, 98% of patients were hospitalized, 54% were admitted to an intensive care unit, and 23% required endotracheal intubation and mechanical ventilation. In other words, this is a medical emergency that can result in respiratory failure in children and can lead to permanent effects in some.
The problem is that the incidence of AFM appears to be trending up this year higher than previously seen. It first started causing concern in 2014, when it was diagnosed in 120 patients in 34 states. Since then, the number of cases has risen in an every-other-year pattern. The CDC confirmed 22 cases in 2015, 149 cases in 2016, 35 cases in 2017 and 238 in 2018.
Interestingly, Enteroviruses are believed to be the most common causes of AFM. Poliovirus is also in the enterovirus (picornavirus) family, so this is no surprise, though multiple other viruses, including West Nile Virus and Adenovirus are known to cause AFM in a small percentage of infected persons as well. This is an important point to take note of; Enterovirus and adenovirus infections are incredibly common, causing about 10-15 million infections every year in the US alone. Infection can cause everything from common cold symptoms to flu-like illness, but most kids do NOT develop AFM. It seems to be a fairly rare idiosyncratic reaction, the underlying cause of which is not yet been fully understood.
The parent of six children and grandparent of 11, the CDC director, Dr. Redfield said he understands the instinct to hope symptoms just go away on their own, but he wants parents to realize that limb weakness is a potentially serious sign that should be evaluated. Dr. Redfield emphasized that the same measures we are taking to prevent Coronavirus infection will help to reduce risk of infection with AFM causing viruses.
In summary, it is wise to call the pediatrician’s office right away to report weakness, change in gait, or pain (especially if in an arm or leg) in the setting of recent fever or respiratory infection.
*It was not mentioned whether the Coronavirus itself could be a potential cause of AFM, but Coronavirus is not in the Enterovirus family.
**I have been following reports of the occurrence of an autoimmune condition called MG (Myasthenia Gravis) following Coronavirus infection. AFM occurs primarily in children, whereas MG occurs predominantly in adults, yet there can be some overlap with regard to how the muscle weakness presents in both conditions. I will post further about MG as more definitive information about this surfaces in the literature.
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Justin Groode MD | Patient Advocate Alliance LLC