Most people are aware that there is a so-called “mystery illness” going around.
A “mystery illness” that is paralyzing some kids.
What’s so mysterious about it?
What is Acute Flaccid Myelitis?
Lots of things are mysterious about acute flaccid myelitis…
We don’t know exactly what causes it, who will get it, why they get it, or how to treat it, etc.
What do we know?
- AFM is not new, although we are seeing more cases lately
- AFM refers to acute (sudden onset) flaccid (droopy or loose muscles) myelitis (inflammation of the spinal cord) and it is a subtype of acute flaccid paralysis
- most cases occur in children, with the ages of affected children ranging from 5 months to 20 years, although some adults have been affected
- these children have a magnetic resonance image (MRI) showing a spinal cord lesion largely restricted to gray matter and spanning one or more vertebral segments
- it is thought that AFM can be caused by viruses (polio, non-polio enteroviruses, West Nile virus, Japanese encephalitis virus, CMV, EBV, adenovirus, etc., environmental toxins, and genetic disorders, and although no common etiology has been found in these recent cases, most experts think that these cases are caused by a neuroinvasive infectious process, likely of viral etiology, including EV-D68 and EV-A71.
- these cases of AFM are not thought to have a post-infectious immune-mediated etiology
- cases are occurring sporadically – after 120 cases in 34 states in 2014, there were only 24 cases in 17 states in 2015, but then 149 cases in 39 states in 2016 and 33 cases in 16 states in 2017. And there have been at least 158 cases in 36 states in 2018, with another 153 cases under investigation.
- outbreaks of EV-D68 and sporadic cases of AFM have also been seen in other countries recently, including Denmark, France, the Netherlands, Spain, Sweden and the United Kingdom (UK)
- most cases occur in the late summer and early fall
- most had symptoms of a preceding viral illness, including respiratory symptoms or diarrhea
- some were unvaccinated
- few were recently vaccinated
- no specific treatments, including steroids, IVIG, plasmapheresis, interferon, and anti-viral medications, have been associated with better outcomes
- some patients have recovered, while many others have persistent paralysis
- there has been at least one death
- some, but not all, were positive for enterovirus D68
- in Colorado this year, 9 of 14 cases were linked to EV-A71 infections
- although there was a national outbreak of EV-D68 in 2014 that coincided with the first AFM cases, we didn’t see the same kind of outbreak in the following years
- AFM isn’t polio, Guillain-Barrésyndrome (GBS), acute disseminated encephalomyelitis (ADEM), or transverse myelitis
- EV-D68 is not new, being first discovered in California in 1962
While that’s a lot of good information, for parents wanting to protect their kids and avoid AFM, there is some key information missing. Same for those wanting to help treat their kids who have or have had AFM.
So although some folks don’t like that it is being called a “mystery illness,” there is still a lot of mystery to it.
But that doesn’t mean that experts aren’t working very hard to take all of the mystery out of AFM.
What Causes Acute Flaccid Myelitis?
Some experts are fairly sure that AFM is caused by an enteroviral infection, to the point that they hope that the CDC focuses work on an enteroviral vaccine.
Which enterovirus though?
At least two different enteroviral infections have been associated with AFM, including EV-D68 and EV-A71.
Why not just make a vaccine to prevent both?
You would first have to make a individual vaccines, before thinking about combining them, and you can’t just make any vaccine you want. If you could, we would have vaccines to protect us against RSV, malaria, HIV, and many other diseases.
Still, since EV-A71 also causes serious outbreaks of hand, foot, and mouth disease in some parts of the world, a vaccine has actually been in development for some time, and two are approved for use in China. That at least means making an EV-A71 vaccine is possible, although we would likely need to make our own.
Why did they make a vaccine for a virus that causes hand, foot, and mouth disease (HFMD)? Because unlike the HFMD that we are used to, which is typically caused by coxsackievirus A16 virus, another enterovirus, when caused by EV-A71, it can be deadly, as we have seen in outbreaks in Asia.
What about an EV-D68 vaccine?
While likely possible, since developing a new vaccine takes a lot of time, we want to be sure that is what is causing the outbreaks.
Do some kids not have either EV-D68 or EV-A71 because it just isn’t detected or because something else is causing them to have AFM? Possibly. One of the biggest issues that is troubling some experts though is that they have not detected these enteroviruses in the spinal cord fluid of many children, as you would expect if the viruses were causing the damage.
But even if these enteroviral infections are the cause, are there other risk factors that make some kids who get these enteroviral infections more predisposed to develop AFM, instead of more typical viral symptoms, like a cold or diarrhea?
And why are we seeing cases now? Did the virus, if that is the cause, just mutate into one that is more virulent?
Hopefully we get some more answers and a way to prevent, treat or cure AFM soon.
Until then, we can make sure we take steps to prevent the known causes of AFM, including polio (get vaccinated) and West Nile virus (use insect repellent), and wash hands properly to help avoid all other viral infections. You also want to get your flu vaccine! The flu can cause Guillain-Barré syndrome, which can also cause AFM.
“…is there any relationship between vaccination status and a developing acute flaccid myelitis? Meaning, are vaccines a risk factor? And the data so far says no, the overwhelming number of children who have gotten AFM have had no recent vaccination of any kind or vaccine exposure. These cases over these years have been happening before flu season and flu vaccination starts, which is one of the questions that comes up, and there hasn’t been any pattern to vaccine exposure of any kind in developing AFM. So far, we have not found a link between the two.”
Benjamin Greenberg, MD on 2018 Podcast on Acute Flaccid Myelitis
And remember, although there are many things we don’t know about AFM, we do know that vaccines do not cause AFM. It would also be great if everyone would get vaccinated so that the CDC and our local health departments could focus on health issues like AFM, instead of still battling measles outbreaks caused by folks who intentionally don’t vaccinate their kids.
What to Know About Acute Flaccid Myelitis
While it might be scary to think that there is a new condition out there that we don’t know everything about, parents should be reassured that experts are actively seeking the cause and a way to both prevent and treat AFM.
More on Acute Flaccid Myelitis
- CDC – Acute Flaccid Myelitis
- CDC – Interim Considerations for Clinical Management of Patients
- CDC – AFM Investigation
- 2018 Podcast on Acute Flaccid Myelitis
- CDC – Transcript for CDC Telebriefing: Update on Acute Flaccid Myelitis (AFM) in the U.S.
- AAP – Acute Flaccid Myelitis in Children
- CDC – Enterovirus D68
- CDC – Enterovirus A71
- Recent Spike in Cases of Acute Flaccid Myelitis
- Clinical Trial – CAPTURE: Collaborative Assessment of Pediatric Transverse Myelitis; Understand, Reveal, Educate
- Clinical Trial – Spinal Cord MRI Research Study for Children, Adolescents, and Young Adults with Myelitis
- Clinical Trial – Understanding Experiences with Vaccination Before and After a Rare Neuro-Immune Disorder
- Transverse Myelitis Association Registry
- A.F.M.- Acute Flaccid Myelitis Awareness & Other Polio-Like Virus Side Effect
- Parents of Children with Polio Like Syndrome / Acute Flaccid Myelitis
- Why health care providers & public health professionals say vaccines are not the cause of recent acute flaccid myelitis (AFM) cases
- Acute flaccid myelitis
- Study – Enterovirus D68 and acute flaccid myelitis-evaluating the evidence for causality.
- The association between acute flaccid myelitis (AFM) and Enterovirus D68 (EV-D68) – what is the evidence for causation?
- Global emergence of enterovirus D68: a systematic review
- Study – Two cases of acute severe flaccid myelitis associated with enterovirus D68 infection in children, Norway, autumn 2014
- Is EV-D68 infection a cause of acute flaccid myelitis in children?
- MMWR – Notes from the Field: Enterovirus A71 Neurologic Disease in Children — Colorado, 2018
- Study – Acute flaccid myelitis: A clinical review of US cases 2012-2015.
- Study – Epidemiology of Recurrent Hand, Foot and Mouth Disease, China, 2008–2015
- Enterovirus 71 infection and vaccines
- A virus-like particle vaccine confers protection against enterovirus D68 lethal challenge in mice.
- Safety, Tolerability and Efficacy of Fluoxetine as an Antiviral for Enterovirus D68 Associated Acute Flaccid Myelitis: A Retrospective Multicenter Cohort Study
- Rhinoviruses and Respiratory Enteroviruses: Not as Simple as ABC.
- Clinical Trial – European Paediatric AFM Associated With EV-D68 Follow-up Study.
- UT Southwestern Transverse Myelitis and Neuromyelitis Optica (TM/NMO) Program
- Johns Hopkins Transverse Myelitis Center
- Boston Children’s Hospital Pediatric Multiple Sclerosis and Related Disorders Program
Updated on December 10, 2018
Last Updated on December 10, 2018 by Vincent Iannelli, MD
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