ATLANTA, Ga. (WPVI) -- There's new information tonight on the current rise in cases of A-F-M - the mysterious illness that can cause paralysis in young children.
The Centers for Disease Control and Prevention says it's now investigating 127 cases of A-F-M, or acute flaccid myelitis - in 22 states.
62 have been officially confirmed.
The disease remains very rare - affecting less than 1 in a million American children.
But that doesn't mean there isn't a lot of concern.
The stories are similar: a child is sick, then within days sudden weakness sets in, with many unable to move their arms and legs.
During a briefing, C-D-C doctors say they're frustrated that lab tests haven't zeroed in on a specific cause for this year's cases of A-F-M.
But they have ruled out polio. And are now looking at a range of potential culprits.
"AFM can be caused by other viruses, such as enterovirus, and West Nile virus, environmental toxins, and a condition where the body's immune system attacks and destroys body tissue that it mistakes for foreign material," said Dr. Nancy Messionnier, the director of the National Center for Immunizations and Respiratory Diseases.
90-percent of the A-F-M cases in 2018 are in kids 18 years or younger.
The average is 4 years old.
Geographically, cases are spread out across the country.
And although A-F-M is reported in other countries, none has the pattern seen in the U-S with a spike in cases every two years seen in late summer-early fall.
The C-D-C says this year's numbers are similar to those in 2014 and 2016.
But investigators aren't any closer to knowing which children are at higher risk of A-F-M, or why.
And another mystery remains - what's the long-term prognosis?
"We know that some patients diagnosed with AFM recover quickly, and some continue to have paralysis and require ongoing care," says Dr. Messonier.
The C-D-C says until more answers are known, parents should take these precautions:
* Everyone in the family should wash their hands frequently
* Make sure everyone has their vaccinations up to date
* Use insect repellent to prevent mosquito bites.
For more information on AFM, click here.
CDC: 127 cases of child paralysis in 22 states under investigation
Extensive lab tests fail to pinpoint one cause for paralysis