The CDC says pediatric acute flaccid myelitis, or AFM, is now affecting young children in 22 states following a recent spike in Minnesota. "Most AFM cases occur in the late summer and fall", which she referred to as "seasonal clustering".
The overall rate of AFM is fewer than one in a million, she said.
"This is a mystery so far", Messonnier said, describing AFM as a "pretty dramatic disease", which preys on a child's nervous system.
Besides viruses, officials are also considering environmental toxins as a possible cause, but so far, they have no evidence that a particular toxin is behind the cases. One child died from AFM in 2017. Officials have been baffled by the increase, and are starting to count suspected cases as well as confirmed ones to better anticipate increases in confirmed cases over the coming months.
"Right now, we know that poliovirus is not the cause", Messonnier said, dispelling reports that AFM was possibly linked to polio. It affects mostly children. Symptoms are sudden arm or leg weakness, difficulty moving facial muscles, slurred speech and trouble swallowing.
The increase in cases appeared to begin in 2014, when the CDC started tracking the illness. In 2016, there were 149 cases. Officials said it's too early to know whether the total for 2018 will surpass those previous years. But the data reported Tuesday represents "a substantially larger number than in previous months this year", Messonnier said. "And certainly after three cycles of this, when we've looked through all the normal agents, we're looking beyond that to see if there are things beyond normal infectious diseases that could cause this", said Messonnier.
More broadly, she noted, "there is a lot we don't know about AFM". Limb paralysis caused by the illness can worsen quickly, so it's also important that individuals experiencing these symptoms receive prompt medical attention. CDC has tested every stool specimen from every AFM patient.
In addition to viruses, potential causes may include environmental toxins and genetic disorders, according to the CDC, and it "can be hard to diagnose because it shares numerous same symptoms as other neurologic diseases".
The MDH says the case is now being reviewed, and did not provide information regarding where in the state this particular case was diagnosed, or whether or not the child is in the hospital.
But the agency doesn't know who may be at higher risk nor why they may be at higher risk. But so far, no pathogen has been consistently detected in the patients' spinal fluid.
There is no specific treatment for AFM, but doctors may recommend physical or occupational therapy to help with arm or leg weakness.
Of the cases announced Tuesday, 62 have been confirmed in 22 states, according to Nancy Messonnier, a top official at the CDC.