20, the CDC had confirmed 38 cases in 16 states, which aren't required to report AFM cases to the CDC. It can follow a viral infection, but environmental and genetic factors may also contribute to its development.
"We have not been able to find the cause of the majority of AFM cases", Messonnier said.
None of the specimens has tested positive for polio virus, however. None of the USA patients tested positive for polio, a crippling and often deadly disease which was eliminated in this country thanks to the polio vaccine. "We are looking beyond the normal infectious diseases that can cause this". The medical name is Acute Flaccid Myelitis, or AFM. The CDC says it counted 22 cases in 2015, 149 cases in 2016 and 33 cases in 2017. That pattern appears to be repeating this year.
There's no vaccine that can protect against AFM-causing enteroviruses.
"This is an emerging condition", said Ryan Wozniak, the surveillance and investigation unit supervisor with the Wisconsin Department of Health Services, where two cases of the disease were just confirmed, News 3 in Madison reported.
The CDC is investigating over 100 possible cases of the disease.
The Louisville Metro Department of Public Health & Wellness is aware of one local case of the polio-like illness, which can cause sudden weakness in the limbs and other neurological symptoms.
In the most severe cases, the muscles that control breathing are weakened to the point the patient requires ventilator.
In most cases, the patient's arms or legs become weak, similar to the results of infection with polio.More news: Trump appears to threaten USMCA deal when lashing out at migrant caravan
Messonnier noted the rarity of the condition, emphasizing that it happens in fewer than one in a million children in the nation.
The disease primarily affects children. Figures show that the average age of an AFM patient is four.
According to the National Institutes of Health, AFM is classified as a rare disease.
Follow-up with patients from the 2014 and 2016 waves has shown that most children do not recover from acute flaccid myelitis, for which there now is no cure.
There is no specific treatment for AFM, the CDC says.
Possible causes being considered include viruses that affect the digestive system called enteroviruses, and possibly strains of rhinoviruses, which cause the common cold, she said. Rehabilitation therapy can help patients regain function. Some treatments such as high doses of steroids are used, but it is not certain they work.
"We understand that people, particularly parents, are concerned about AFM", said Messonnier, director of the National Center for Immunization and Respiratory Diseases.