There are now 62 confirmed reports of acute flaccid myelitis, or AFM, an illness similar to polio, across 22 states in the U.S., according to the Centers for Disease Control and Prevention.
As of Sept. 20, the CDC had confirmed 38 cases in 16 states, which aren't required to report AFM cases to the CDC.
This year's numbers are similar to 2016 and 2014. Since 2014, 386 cases have been confirmed, the CDC said on Tuesday. Currently, 127 patients are under investigation. The average age of those afflicted is 4, and 90 percent of those with AFM are 18 or younger.
"This remains a rare syndrome, but the similarities to poliomyelitis, polio-like illness, are concerning and bear close monitoring," Dr. Todd Ellerin, director of infectious diseases at South Shore Hospital in Weymouth, told ABC News in an interview. "Now is it going to be as widespread as that? Hopefully not. And that's why we have to keep our eye on this."
Acute flaccid myelitis affects the spinal cord and can cause partial paralysis. It mostly afflicts children and young adults and can be caused by toxins in one's environment, genetic disorders or viruses such as poliovirus, West Nile virus or adenovirus.
Another potential cause of AFM is a type of enterovirus called EV D68, Todd said.
"That's important because enteroviruses cause the common cold," Ellerin said. "It causes fever illnesses in the summer and fall, often associated with rashes. It causes hand, foot and mouth disease. It causes a lot of what [are] typically very mild sort of nuisance type diseases."
Typical symptoms of AFM are similar to those of a severe respiratory illness, along with a fever, but those often progress into neurological symptoms. Some with AFM will feel weakness in their arms or legs, a loss of muscle tone or slower reflexes. The most severe symptom is respiratory failure.
People can protect themselves from contracting AFM using methods similar to preventing getting the flu, Ellerin said.
So far the disease has claimed one life in the U.S.
Ellerin said the staff at his hospital has been trained to recognize symptoms, and he encourages medical centers to train employees similarly before it's too late.
"We want to see that education," he said, "in order to have early recognition and detection."