There is no known cause or treatment, a state Department of Public Health advisory said.
The CDC says that there has been an increase in cases of AFM since 2014.
Doctors say the most serious cases can lead to respiratory failure.
"We understand that people, particularly parents, are concerned", said Dr. Nancy Messonnier, director for the CDC's National Center for Immunization and Respiratory Diseases, during a teleconference call with reporters. Another spike came in 2016.
"There is a lot we don't know about AFM, and I am frustrated that despite all of our efforts", she said, "we haven't been able to identify the cause of this mystery illness". Another kind of virus was found in only some of the cases.
Some patients have quickly recovered, but one child who contracted AFM - which affects the nervous system via the spinal cord - died past year. Symptoms also can include facial droop and weakness, difficulty moving the eyes, drooping eyelids or difficulty swallowing and slurred speech. "Most AFM cases occur in the late summer and fall", which she referred to as "seasonal clustering". The benefit of seeking medical care is to attend to kids' symptoms, which can include respiratory failure, Science News reports, but there is now no cure for AFM.
Like other neurological diseases, such as Guillain-Barre syndrome, physical therapy or occupational therapy are the only treatment options for people with AFM.
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MA has seen a total of 16 confirmed cases in children since 2014, plus one probable case in an adult. Scientists are investigating a number of causes, including viruses, environmental toxins and genetic disorders, the CDC said on its website.
"We know that some patients diagnosed with AFM have recovered quickly and some continue to have paralysis and require ongoing care".
Because officials don't know the cause of AFM, they can't recommend a specific way to prevent it.
"My husband that noticed her arm was kind of just hanging there", her mother, Carlene, said.
Kelly Tunan's 5-year-old son was diagnosed with the disease in 2015 and had to undergo several surgeries on his right leg and right foot.
"It's not something to really panic about its exceedingly rare, but it is something they want physicians and hospitals to be aware of so that if they do see cases, they get reported and hopefully the testing can find out what's causing it", said Mark Rasnake, who is an infectious disease physician.
"Early intervention is definitely always helpful".