What we know about the mysterious polio-like illness spreading across the US

What’s causing AFM is unclear.
What’s causing AFM is unclear.
Image: Reuters/Tami Chappell
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The US Centers for Disease Control now says there have been 62 confirmed and 65 suspected cases of the mysterious condition known as acute flaccid myelitis (AFM).

Cases of AFM—which affects the spinal cord—have risen substantially in the US in the past couple of months, Nancy Messonnier, director of the CDC’s Center for Immunization and Respiratory Diseases, said today (Oct. 16).

Usually after just a mild cold or fever, the condition weakens or paralyzes limbs. Often patients—most of whom are children—recover, but sometimes this paralysis can be permanent. One child in the US died from the condition in 2017.

“This is actually a pretty dramatic disease,” Messonnier said. “These kids have a sudden onset of weakness and they are generally seeking medical care and being evaluated by neurologists, infectious-disease doctors and their pediatricians and coming to public-health awareness.”

It’s unclear what causes AFM. The CDC, which has only collected data on 362 cases confirmed since 2014, estimates there are usually less than one case per million people each year. It’s widely suspected that AFM is related to the viruses that cause polio and West Nile. However, none of the patients with AFM have tested positive for polio, and Messonnier said that West Nile is not the cause. Scientists also believe it could be related to genetic or environmental factors but are unsure how.

Although there isn’t an official state-by-state count, there have been 14 cases in Colorado, eight in Texas, six in Minnesota, five in Maryland, and three in New Jersey. Over half of US states have suspected or confirmed cases, according to a survey conducted by CNN.

At the moment, there is no treatment for AFM. Healthcare providers can only try to mitigate symptoms of patients with the hope that they recover.

Correction (Oct. 18): An earlier version of this article said that there are less than one million cases of AFM annually. It is actually less than one case per million people.