At least 72 children across the U.S., including six in the District of Columbia, have contracted a rare polio-like disorder this year, and health officials expect that number to increase.
Doctors do not know the cause of acute flaccid myelitis (AFM) but have recorded a spike every two years in the number of children contracting it around the end of summer and the beginning of autumn.
“We keep saying ‘we believe’ and ‘we have a strong suspicion.’ That’s the frustrating aspect,” said Dr. Anthony S. Fauci, head of the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health. “We don’t have definitive proof.”
AFM is characterized by sudden paralysis or weakness in the limbs, and swelling of the spinal cord. Since 2014, the Centers for Disease Control and Prevention has recorded 396 cases of the illness, which affects fewer than 1 in 1 million people.
The disease affects mostly children ages 4 to 7 but is also present in adolescents and adults.
Instances of AFM first started appearing in 2012, said Dr. Roberta L. DeBiasi, chief of the Division of Pediatric Infectious Diseases at Children’s National Health System in Washington.
But it wasn’t until 2014, when doctors in California and Colorado identified an uptick in cases — 24 and 10, respectively — that the CDC was notified of an outbreak.
The CDC launched an investigation and tracked 120 AFM patients across 34 states. Some cases were reported in 2015, but a spike was observed in 2016, especially around autumn, with 149 cases across 39 states and the District of Columbia. Last year, 33 cases across 16 states were confirmed.
So far this year, 72 cases have been confirmed across 24 states and the District.
“We’ve seen them all through the period,” Dr. DeBiasi said of AFM patients treated at Children’s National Hospital over the past four years.
The hospital has treated 12 cases of AFM since 2013. Half of the cases were diagnosed this year.
Doctors and researchers have theorized that AFM is triggered by contraction of a respiratory illness, in particular the enterovirus D68 (EV-D68).
Because of the increased focus on AFM, the National Institute of Allergy and Infectious Diseases is ramping up its genetic research on enteroviruses, of which there are hundreds, Dr. Fauci said.
The CDC has not confirmed finding a specific disease-causing pathogen that is common to all AFM cases across the country but recorded its highest number of children and adolescents with EV-D68 in 2014 — a total of 1,149 cases in 49 states and the District of Columbia.
Scientists found an association between the outbreak of EV-D68 in 2014 and the higher than usual number of cases of AFM that year, according to a research paper published in the journal The Lancet Infectious Diseases in 2015.
“These findings strengthen the putative association between enterovirus D68 and acute flaccid myelitis and the contention that acute flaccid myelitis is a rare yet severe clinical manifestation of enterovirus D68 infection in susceptible hosts,” the researchers wrote.
A CDC report in 2016, published in the journal Clinical Infectious Diseases, echoed the findings that the 2014 AFM cluster was “likely associated with the large outbreak of EV-D68-associated respiratory illness.”
AFM and Prozac
The fact that AFM predominantly affects children is another clue that its trigger is an infectious disease, Dr. DeBiasi said.
“If I’m 40 years old and I’ve had 60 of the hundred known enteroviruses at some point in my life, maybe I can fight off this new D68 better than a 4-year-old who’s never been exposed to any enteroviruses,” she said. “That’s sort of an example of how immunity can play a role in an illness.”
The long-term consequences of the enterovirus are unknown. Physicians and researchers have gathered data on a relatively small group of patients since 2014.
Dr. DeBiasi said parents typically bring their AFM-affected children to an emergency room when they notice paralysis or weakness in their arms or legs. The children then are tested for inflammation of the spinal cord — either via an MRI or a spinal tap — and are transferred to a neuro-intensive-care unit for monitoring and follow-up.
The first line of treatment is almost always intravenous immunoglobulin (IVIg), a transfusion of blood plasma with antibodies to boost the immune system, Dr. DeBiasi said.
“The idea there is that it can both tone down inflammation and it can also provide protective antibodies to standard things that the general public are exposed to, including enteroviruses,” she said.
An additional treatment for more serious cases is plasmapheresis — filtering blood to remove any circulating antibodies — but the procedure hasn’t shown any benefit, the pediatric specialist said.
The prognosis is grim: Only a small minority of patients ever fully recover, Dr. DeBiasi said. About half of AFM patients show significant improvement but suffer from lingering effects — trouble walking or weakness in the affected limbs — and the other half never fully recover.
“There really is a big spectrum of improvement or not, but a large majority don’t get completely back to normal,” she said.
Doctors at Children’s Hospital Los Angeles have performed nerve transfer surgery for at least one patient suffering from AFM, CBS News reported. In the case of a 4-year-old girl who had lost strength in her right arm, surgeons transferred nerves from her rib and diaphragm to help mobility in her elbow, wrist and fingers.
Another line of treatment doctors are exploring is the use of fluoxetine, typically known as the antidepressant Prozac. In lab trials, researchers treated isolated strains of EV-D68 with fluoxetine and found that it inhibited the replication of the enterovirus. The idea was that the medication would kill the virus that possibly triggers the AFM.
But in a study of 56 children with AFM, researchers observed no noticeable improvement among those treated with fluoxetine. A summary of their results was presented last month at an annual conference on infectious diseases.
Dr. DeBiasi said these results don’t rule out fluoxetine as a helpful medication. She said the patients who received the treatment had more severe cases of AFM and were unlikely to reap any small benefit.
“If you compare the group, the overall number — the weakness scale of the kids who got the Prozac — those tended to be the kids that were more severe to begin with,” she said. “If you’re a doctor and you’re taking care of children, if they’re doing great or not too bad, you may not start thinking of using experimental therapies, whereas if you have someone who’s really doing poorly, you might be more inclined to try something.”
With scientists unable to say what exactly is causing AFM, prevention advice is nonspecific. The CDC recommends that children be up to date on vaccinations for polio and West Nile virus and practice good hand hygiene. If the trigger is a virus, then killing germs before they can infect is a good step in preventive care.
“Even though it sounds kind of generic, it really is the best way to prevent infection,” Dr. DeBiasi said.
She wants the public to understand that AFM remains extremely rare, even though the U.S. is recording an uptick in the number of cases. Polio outbreaks were rampant before a vaccine was developed, she said.
“There were 10,000 to 20,000 cases a year, every single year in children, when polio virus was circulating,” Dr. DeBiasi said. “So this is still very, very rare compared to that. We’re talking 100 to 150 cases every other year.
“It doesn’t mean that it’s not severe or that we don’t care about the 100 kids it occurs in. I mean, we really do care and want to find the cause and the cure.”
