It has received reports of 127 patients under investigation for the condition. Outbreaks are most common from August to October, and over 90 percent of the cases have involved children under 18 years old, with the average age of those inflicted standing at just 4 years old.
"At this time we don't have a way to determine which children may be at an elevated risk for developing AFM, or the underlying explanation that predisposes them to develop AFM in the first place", he said.
The condition is not new, but the CDC said it saw an increase in cases beginning in 2014.
Health officials don't have an exact cause of AFM. In total, there have been 386 confirmed cases since 2014.
AFM grabbed attention in 2014, when 120 cases were reported nationally. In 2017, one person died of AFM.
The other three suspected cases in Arkansas are in Central Arkansas and Southwest Arkansas.
The long-term effects of the disease are also unknown.
The rare illness affects the nervous system and spinal cord, causing muscle-weakness and reflexes in the body to weaken.
Similar neurological conditions are known to be caused by viruses, environmental toxins and genetic disorders.
Geography also does not appear to be a factor, with the confirmed cases spread across 22 of the 50 USA states.
States are reporting their cases to the CDC, Messonnier said.
A seventh child has been diagnosed with a rare, paralyzing illness that has seen an uptick in cases this year in the USA, the Minnesota Department of Health said. "But the appearance of the AFM symptoms is actually very rare".
Some children with AFM recover full motion and strength-usually within a few months-whereas in others the nerve damage seems permanent, she says.
Although it's rare, the CDC recommends seeking medical care right away if you or your child develop sudden weakness of the arms or legs.
Once diagnosed, some patients have recovered quickly, but some continue to have paralysis and require ongoing care, Messonnier said.
Although symptoms resemble polio, no evidence of poliovirus has been found in specimens from any case diagnosed so far, Messonnier said.
CDC officials have not confirmed that enterovirus D68 causes AFM.
The cases this year seem to be spread across much of the country, as were the earlier two waves. They also suggested that children stay up-to-date with their vaccines and practice good hand-washing habits. Several cases have been linked to enteroviruses or other germs, but officials have not been able to find a cause for the majority of the cases. Although there is no definitive diagnosis, doctors can identify AFM from a combination of symptoms and an MRI scan, which can reveal spine inflammation. To date, no pathogen has been consistently detected in AFM patients.
There is no specific treatment for the virus.
Massachusetts General Neurology Department Director Dr. Marcelo Matiello urged parents who see any of these symptoms to get their children to a neurologist without hesitation. She noted the confirmed cases are in 22 states.