A spike in the number of children with a rare neurological disease that causes polio-like symptoms has health officials across the country scrambling to understand the illness. Yet, more than 4 years after health officials first recorded the most recent uptick in cases, much about the national outbreak remains a mystery.
Courtesy Centers for Disease Control and Prevention
Acute flaccid myelitis (AFM) affects the gray matter in the spinal cord, causing sudden muscle weakness and a loss of reflexes. The illness can lead to serious complications – including paralysis or respiratory failure – and requires immediate medical attention.
The Centers for Disease Control and Prevention is investigating 127 cases of possible AFM, including 62 that have been confirmed in 22 states this year. At least 90% of the cases are among patients 18 years old and younger. The average age of a patient is 4 years old.
AFM remains extremely rare, even with the recent increase. The CDC estimates fewer than 1 in a million Americans will get the disease. Officials advised parents not to panic but remain vigilant for any sudden onset of symptoms. They also suggested that children stay up to date with their vaccines and practice good hand washing habits.
This year’s outbreak marks the third spike of AFM in 4 years. From August 2014 to September 2018, 386 cases have been confirmed. Yet, experts still do not understand crucial aspects of the disease, including its origins and who is most at risk.
“There is a lot we don’t know about AFM,” said Nancy Messonnier, MD, director of the National Center for Immunization and Respiratory Diseases. Here’s what puzzles health officials about AFM:
The cause is still unknown
Acute flaccid myelitis can be caused by viruses, such as polio or West Nile. But federal officials said that those viruses have not been linked to the U.S. outbreak over the past 4 years. They have not isolated the cause of these cases.
Despite symptoms reminiscent of polio, no AFM cases have tested positive for that virus, according to the CDC. Investigators have also ruled out a variety of germs. Environmental agents, viruses, and other pathogens are still being considered.
The 2014 outbreak of AFM coincided with a surge of another virus that caused severe respiratory problems, called EV-D68. However, the CDC could not establish a causal link between AFM and the virus. Since then, no large outbreaks of the virus have occurred, according to the CDC.
Carlos Pardo-Villamizar, MD, a neurologist and director of the Johns Hopkins Transverse Myelitis Center, said that the mystery lies in whether the damage seen in AFM is caused by an external agent or the body’s own defenses.
“At this moment, we don’t know if it’s a virus that is coming and producing direct damage of the gray matter in the spinal cord,” he said, “or if a virus is triggering immunological responses that produce a secondary damage in the spinal cord.”