Mysterious Polio-like illnesses baffles medical experts while frightening parents | Get Healthy

Acute flaccid myelitis, or 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 Federal 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 percent of the cases are among 18 and younger patients. The average patient age is 4 years old.

AFM remains extremely rare, even with the recent increase. The CDC estimates fewer than 1 million Americans will get the disease. Officials not yet on the verge of alertness for any sudden onset of symptoms. They also suggest that children stay up-to-date with their vaccines and practice.

This year's outbreak marks the third spike of AFM in four 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 do not know about AFM," said Dr. Nancy Messonnier, 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 these viruses have not been linked to the U.S. outbreak over the past four years. They have not isolated the cause of these cases.

AFM cases have tested positive for that virus, according to the CDC. Investigators 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 severe seizure of respiratory viruses, called EV-D68, however, the CDC could not establish a causal link between AFM and the virus. Since then, no large outbreaks of viruses have occurred, according to the CDC.

Dr. Carlos Pardo-Villamizar, a neurologist and director of the Johns Hopkins Transverse Myelitis Center, said the mystery lies in whether or not the cause of self-injury is the result

"At this moment, we do not know if it is a virus that is coming into the world of spinal cord," he said, "or if a virus is triggering spinal cord. "

It's not clear who is at risk, or why

Although the disease appears to be a certain age group, the federal disease experts do not know who is likely to get acute flaccid myelitis.

Pardo-Villamizar said identifying vulnerable populations is "a work in progress."

Dr. Mary Anne Jackson, a pediatric infectious disease specialist and interim dean of the School of Medicine at the University of Missouri-Kansas City, said many of the patients were healthy before falling ill with the disease. It suspects that a host of factors play a role in the likelihood of getting AFM.

The long-term effects are unknown.

The CDC said it does not know how long symptoms of the disease will last for patients. However, experts say that initial indications from a small number of boxes suggest a grim outlook.

A study published last year found six of eight children in Colorado with acute flaccid myelitis still struggles with motor skills one year after their diagnosis. Nonetheless, the researchers found that patients and families "demonstrated a high degree of resilience and recovery."

"The majority of these patients are left with extensive problems," said Pardo-Villamizar, who was not involved in the study.

Jackson, who also saw muscle weakness in her patients, said she believes the CDC may be hesitant to specify the long-term effects of this disease. More studies that include a greater proportion of confirmed cases.

Kaiser Health News is a national health policy news service. It is an editorially independent program of the Henry J. Kaiser Family Foundation which is not affiliated with Kaiser Permanente.