By Kathleen Doheny
WebMD Health News
Reviewed by Brunilda Nazario, MD
Oct. 10, 2016 -- A rare but serious illness that causes paralysis in children appears to be on the rise this year, the CDC has warned.
Acute flaccid myelitis, or AFM, has affected 50 people so far this year, most of them children. It's characterized by sudden muscle weakness, often following a respiratory illness or fever. In some cases, the paralysis has been permanent. The illness is mystifying scientists and scaring parents.
"We still have a lot to learn about the causes, risk factors, and outcomes of AFM, and CDC is intensifying efforts to better understand these questions," says Manisha Patel, MD, MS, a pediatric infectious disease specialist at the CDC.
WebMD turned to Patel and another infectious disease expert to find out more about this condition.
What Is AFM? What Are the Symptoms?
"The key symptom is sudden onset of weakness in the arms and legs," says Patel. There is no pattern, she says, as the weakness can affect several limbs or a single one.
"In some situations, you can have facial drooping or difficulty swallowing or speaking," she says.
There can also be neck stiffness, says Amesh Adalja, MD, a spokesman for the Infectious Diseases Society of America and an infectious disease expert at the University of Pittsburgh Medical Center.
Numbness or tingling is rare, the CDC says, although some have pain in their arms and legs. Some people with AFM are unable to pass urine.
In severe cases, the muscles that control breathing get weak. "There are some instances where patients can progress to respiratory failure within a week or so of their initial weakness, but in rarer cases, this can be more rapid onset," Patel says.
In addition to an MRI, acute flaccid myelitis can be diagnosed with the help of nerve response tests and testing of the fluid around the brain and spinal cord, the CDC says.
What Causes It?
Several different types of viruses are believed to trigger AFM, including enteroviruses, adenoviruses and West Nile virus. But scientists don't know what's causing these specific cases, Patel says. It's unclear why some children get AFM after an infection while others don't.
Enteroviruses include polio viruses and other viruses, like ones that cause hand, foot, and mouth disease, viral conjunctivitis (pinkeye), or viral meningitis. Adenoviruses trigger respiratory illness and cold-like symptoms such as sore throat, bronchitis, and diarrhea.
"We are also looking at environmental causes," Patel says, but scientists haven't narrowed down anything specific. Often, a cause can't be found, the CDC says.
A cluster of AFM cases was reported in 2014 at the same time as an outbreak of a severe respiratory illness in children caused by enterovirus D68 (EV-D68). At the time, scientists thought the two might be linked. But experts now say it's not clear whether the EV-D68 was a coincidence or actually caused the acute flaccid myelitis.
However, AFM remains extremely rare -- less than one in a million, Patel notes.
And it's only one of a number of conditions that trigger limb weakness, the CDC says.
Can Adults Get It?
Yes, but it is much more likely to affect children. "Over 90% of the cases this year have been in children less than 18 years of age," Patel says.
"Younger kids are more likely to be infected," according to Adalja, because they typically haven't built up as much immunity to germs as adults.
Why Might It Be on the Rise?
Scientists aren't sure. "We're trying to understand that," Patel says.
Heightened surveillance may play a role, Adalja says.
From August through December 2014, after the CDC began tracking AFM cases, 120 people in 34 states were diagnosed with it. In 2015, cases fell to 21 people in 16 states, the CDC says. But cases rose again this year -- through August, 50 people in 24 states have been confirmed to have AFM.
No deaths have been reported, the CDC says. And while the 2016 case count remains below that in 2014, the agency says it's concerned about the increase.
When Should You Seek Medical Help?
Seek treatment as soon as possible if you see any symptoms of AFM, the CDC advises. "If you see your child is not using his arm," Patel says, call your pediatrician or go to the emergency room.
There is no specific treatment, other than what doctors call supportive care, treating symptoms. This might include physical and occupational therapy for limb problems, Adalja says.
Do Those Who Have It Get Their Limb Movement Back?
Some do, the CDC says. The agency did a survey of patients from the 2014 investigation and got 56 responses. A small number had complete recovery of limb function after about 4 months, but some had no improvement.
According to Patel, no long-term information is available on those children, but the CDC is working with the states to collect the information.
Is There Any Way to Prevent It?
Good hand hygiene to minimize exposure to germs is one measure, Adalja says. Disinfecting household surfaces is advised, Patel says. Those measures can reduce your odds of catching a virus.
Being up to date on vaccinations is another recommendation, as is protecting yourself from mosquitoes, since viruses like West Nile, spread by mosquitoes, are thought to trigger AFM, Patel says.
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