Medical researchers fear that more children will develop paralysis from a mysterious polio-like illness that has struck every two years since 2014.
The condition, known as acute flaccid myelitis, or AFM, is rare and has reached its peak for 2018. It will likely continue to fade as winter approaches. But many believe it will be back.
"AFM is here, and it doesn't seem to be going anywhere," said Dr. Benjamin Greenberg, a neurologist at UT Southwestern Medical Center's Peter O'Donnell Jr. Brain Institute and at Children's Health.
When a cluster of children in the U.S. developed unexplained paralysis in 2014, doctors hoped the outbreak was a freak event. Then, in 2016, more people came down with the same set of symptoms. This year, AFM struck a record 165 people, the majority of them young, previously healthy children
Texas has reported 27 cases in 2018, according to the Texas Department of State Health Services, including five in Tarrant County, three in Collin County and two in Dallas.
Experts say we should expect the condition to return again in 2020, following a pattern of sickening patients every other year from summer through fall.
Investigators at the U.S. Centers for Disease Control and Prevention say they do not yet know what triggers the paralysis
"As a mom, I know what it's like to be scared for your child, and I understand parents want answers," Dr. Nancy Messonnier, director for the National Center for Immunization and Respiratory Diseases, said at a November news conference. "CDC is a science-driven agency. Right now the science doesn't give us an answer."
To gear up for another possible outbreak, the agency formed an AFM task force. It has funded state health departments to boost surveillance and is educating doctors about what to look for and test for when patients present with unexplained limb weakness.
"It is impossible to say if we'll have any real answers [by 2020], because this a complex public health challenge," said Dr. Thomas A. Clark, a medical epidemiologist who is leading the CDC's response to AFM, in a statement to The Dallas Morning News."Until we fully understand what causes AFM, we can't help protect people against it."
Many experts, including Greenberg, say the agency has been slow to name viruses as a probable cause.
The 2014 AFM outbreak coincided with the largest national outbreak of a virus known as D68, which had previously been associated mainly with respiratory infections. Forty-two percent of AFM patients tested in 2018 were found to have D68 in their nasal passages.
Experts point to other evidence that makes D68 a likely culprit. Like polio, D68 is an enterovirus, part of a large group of common pathogens that cause colds, stomach bugs, eye infections, and hand, foot and mouth disease. Like AFM, enteroviruses exhibit cyclical patterns. Polio, too, sickened most children in late summer and fall. And almost all AFM patients had fevers and other cold symptoms three to 10 days before becoming paralyzed.
"We are in a place to say a significant portion, if not the majority, of AFM cases that occur between August and November every other year are due to a virus, and likely an enterovirus, and likely D68," said Greenberg, an expert on spinal cord inflammation who has been treating and following AFM patients since the outbreak began. He is a member of the CDC task force.
"I don't think it's 100 percent," he said. "But I would like to see the language at least embrace that."
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