"Despite extensive laboratory testing, we have not determined what pathogen or immune response caused the arm or leg weakness and paralysis in most patients", Dr. Nancy Messonnier from the CDC told NBC News. It can lead to serious neurological problems, the CDC said in a statement last week. "CDC has been actively investigating these AFM cases, and we continue to receive information about suspected AFM cases". (Of the 155 cases this year, 62 are confirmed in 22 states).
"This remains a rare syndrome, but the similarities to poliomyelitis, polio-like illness, are concerning and bear close monitoring", says Dr Todd Ellerin, director of infectious diseases at South Shore Hospital in Weymouth, according to Yahoo!
That's an increase of 28 cases in a matter of days. "We have not confirmed the cause for the majority of these cases", the agency said.
Ohio's reported cases occurred in Columbiana, Cuyahoga, Mercer and Pickaway counties in August and September, and all affected boys from 1 to 13 years of age, according to the Centers for Disease Control and Prevention and the state health department.
"I am frustrated that despite all of our efforts we haven't been able to identify the cause of this mystery illness", said Messonnier.
HuffPost Canada has reached out to the Canadian Paediatric Society for comment.
The trigger for the condition is unknown, but MRI imaging shows that those with AFM have an inflammatory abnormality in a region of the spinal cord called the anterior horn cell. But there are many enteroviruses, and they usually cause symptoms similar to the common cold, as do rhinoviruses, adenoviruses and many other viruses.
The average age of those diagnosed is 4 years old.
"We don't know who may be at higher risk for developing AFM or the reasons why they may be at higher risk". We don't fully understand the long-term consequences of AFM.
Health officials say there are several potential causes of the condition, including certain viruses, environmental toxins, and genetic disorders. While potential causes may include certain viruses, environmental toxins and genetic disorders, the CDC says, "AFM can be hard to diagnose because it shares numerous same symptoms as other neurologic diseases".
Parents should seek medical care right away if a child develops symptoms of AFM, which include sudden weakness and loss of muscle tone in the arms or legs.