Researchers have pinpointed enterovirus as the likely cause of acute flaccid myelitis, the polio-like condition affecting young children across the country, according to a study published in Nature Medicine.
The CDC has confirmed 590 cases of acute flaccid myelitis in the U.S. since 2014, including 236 confirmed cases across 41 states in 2018. The condition impairs the nervous system, specifically affecting the gray matter in the spinal cord. It can cause permanent paralysis in children.
Researchers have not been able to definitively point to a cause, although previous research indicated that it could be enteroviruses, a group of viruses that includes poliovirus.
Now, a research team — led by scientists from University of California San Francisco — has identified clear signs of enterovirus in nervous system of acute flaccid myelitis patients, providing the strongest evidence of the condition's cause thus far.
The researchers used an enhanced version of a virus-hunting tool to examine spinal fluid obtained from 42 children with acute flaccid myelitis and 58 control patients, who were diagnosed with other neurological diseases.
They found antibodies against enterovirus in the spinal fluid of nearly 70 percent of acute flaccid myelitis patients, compared to less than 7 percent of the control patients who tested positive for those antibodies.
"When there's an infection in the spinal cord, antibody-making immune cells travel there and make more antibodies," said Ryan Schubert, MD, a clinical fellow in UCSF's department of neurology and lead author of the study. "We think finding antibodies against enterovirus in the spinal fluid of AFM patients means the virus really does go to the spinal cord. This helps us lay the blame on these viruses."
However, researchers are still investigating why fewer than 1 percent of infected children get acute flaccid myelitis when enteroviruses are extremely common. They are also still trying to figure out why acute flaccid myelitis only affects children.