What causes A.F.M.?
The exact reasons that the condition appears are not known, but neurological conditions have a variety of triggers, such as viruses, environmental toxins and genetic disorders, the C.D.C. said.
In 2014, doctors believed the cases might be linked to infection with enterovirus 68, a respiratory virus, according to a New York Times article. A statement on Tuesday from the Colorado Department of Public Health and Environment said that enterovirus 68 and another type, enterovirus 71, had been found in all but two of the state’s A.F.M. cases this year.
“There were not necessarily a lot of cases that had been noticed before” 2014, said Jayne Griffith, the Minnesota Department of Health’s senior epidemiologist. “So at that point, where it burst onto the scene, the C.D.C. took initiatives to make this condition reportable.”
Ms. Griffith said the cases usually come to light when parents notice acute muscle weakness or paralysis in their child and bring them to a health provider. A clinical diagnosis, which was given in the state’s six new cases, involves an M.R.I. and a scan or a tap of the spine, which detects inflammation associated with A.F.M.
“There is obviously a lot of concern about it, but it is rare,” Ms. Griffith said.
Cynthia Kenyon, another Minnesota Department of Health epidemiologist, said that spinal inflammation disorders could spring from viruses, other pathogens or toxins. After a diagnosis is made, health providers and investigators try to retrace the path of the illness to its source.
“From what my understanding is, if there is an external causal agent, it may be difficult to determine when the exposure to that agent occurs,” Ms. Kenyon said. “And then there is lag time until the spinal inflammation.”
Investigators are still collecting data on the two unconfirmed cases in Minnesota, which involved children under the age of 10 who displayed symptoms in the summer, Ms. Griffith said.