The federal agency said similar waves of the illness occurred in 2014 and 2016.
At least 65 other illnesses around the US were being investigated as possible cases.
The cause of the disorder has not yet been identified. Enterovirus (EV) D68, a virus from the same family as polio, is the leading suspect, having been closely linked to the 2014 outbreak, Pardo-Villamizar said. Fall 2018 represents the third surge of AFM cases, which seem to spike in late summer and early fall, as Buzzfeed notes. But the data reported Tuesday represents "a substantially larger number than in previous months this year", Messonnier said. In addition, officials do not yet know the long-term effects of AFM.
According to the Center for Disease Control, AFM "affects the nervous system, specifically the area of spinal cord called gray matter, which causes the muscles and reflexes in the body to become weak".
She said the CDC and research partners are casting a wide net trying to figure out what is causing the rise in cases, suggesting scientists have been looking at a variety of viruses and even environmental toxins in their search. Fifteen states said they'd confirmed cases this year.
"We know this can be frightening for parents", Messonnier said.
Parents should seek immediate medical care for kids exhibiting AFM symptoms, Messonnier said at the press conference, according to STAT.
Some patients recover quickly, while others experience paralysis and require ongoing care.
Health experts have ruled out some causes, including poliovirus and West Nile virus.
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The CDC says that there has been an increase in cases of AFM since 2014.
The two cases this year were in the southern and southeastern parts of the state.
"Our medical team has been reviewing vaccine records when available during this year's investigation and do not see a correlation", said CDC spokeswoman Kristen Nordlund.
In September, Pardo-Villamizar and his colleagues published a follow-up of 16 patients stricken in 2016 that concluded that "the majority of children with AFM have limited motor recovery and continued disability".
"Despite extensive laboratory testing, we have not determined what pathogen or immune response caused the arm or leg weakness and paralysis in most patients". CDC has tested every stool specimen from every AFM patient.
There is no specific treatment for AFM, according to the CDC, although neurologists might recommend things like physical therapy to help treat muscle weakness on a case-by-case basis.
The CDC says there are preventative measures people can take to reduce the risk of infections that could lead to AFM. "You don't need an very bad lot of paralyzed children to make this an important problem". She noted the confirmed cases are in 22 states.
The CDC referred calls to individual state health departments. In 2015 and 2017, the counts of reported illnesses were far lower.
This article was originally published by The Washington Post.