The CDC is investigating about 160 additional reports of children with possible acute flaccid myelitis, but are still puzzled by the sudden spike in cases, according to STAT.
Health officials have confirmed 90 cases of AFM, a condition damaging the gray matter insulating the spinal cord, which leads to muscle weakness and paralysis in a limb or multiple limbs.
The CDC has yet to find what's causing the 2018 spike in cases. Nancy Messonnier, MD, director the CDC's National Center for Immunization and Respiratory disease, is considering whether the condition is caused by an "aberrant immune response to an infection," instead of the infection itself.
Scientists also are considering if the illness is undetectable due to a pathogen hiding in the patient's body or if the pathogen has "cleared" the body when limb weakness develops, according to STAT.
"We’re not sure if the reason we’re not finding pathogens in all of these patients is because it’s cleared [from their systems]. Is it because it’s hiding? Is it because it’s something we haven’t tested for?" Dr. Messonnier told STAT. "What we do know is that these patients had fever and respiratory symptoms three to 10 days before their limb weakness. And we know that it’s the season where lots of people have fever and respiratory symptoms. What we need to sort out is what is the trigger for the AFM."
In 2014, when reported AFM cases spiked in the U.S., health officials confirmed 120 of them, and they coincided with an enterovirus outbreak. Researchers noted an increase of AFM cases appeared to follow a pattern: There is a year with a high number of cases followed by a year with only a few AFM cases. The CDC speculates 2018 is a year of high cases.
On Nov. 13 the CDC issued a report analyzing 106 pediatric patients who suffered from rapid onset limb weakness. Of that group, 80 were confirmed to have AFM, six were probable cases, and the last 20 patients did not have AFM, but had other confirmed viruses.
Dr. Messonnier told STAT that finding a pathogen in the spinal fluid would be considered strong evidence for potentially causing AFM. Normally there would not be any bacteria or virus in spinal fluid, and by taking respiratory tract swabs or checking stool samples, tests can pick up a number of viruses present within the body that are not contributing to AFM.
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