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This special episode of That’s Pediatrics tackles a subject currently on the minds of pediatricians and parents alike: Acute flaccid myelitis (AFM). This rare childhood neurological disorder causes weakness in the arms or legs — sometimes even paralysis. John Williams, MD, our division chief of Pediatric Infectious Disease at UPMC Children’s Hospital of Pittsburgh, talks about the recent outbreak of AFM with enterovirus virologist Carolyn Coyne, PhD, and Brian Martin, DMD, VP of Medical Affairs.
View the transcript for this podcast (PDF)
Speaker 1: This podcast is for informational and educational purposes only and is not to be
considered medical advice for any particular patient. Clinicians must rely on
their own informed clinical judgments when making recommendations for their
patients. Patients in need of medical advice should consult their personal
Carolyn Coyne: I'm Carolyn Coyne. I'm a scientist in the Division of Pediatric Infectious Diseases.
Brian Martin :I'm Brian Martin , Vice President of Medical Affairs here at UPMC Children's Hospital of
Pittsburgh. Today we're fortunate to bring you a special edition of That's
Pediatrics, featuring Dr. John Williams, Division Chief of Pediatric Infectious
Disease here at Children's. Our topic is acute flaccid myelitis, a condition that's
been top of mind for many parents, clinicians, and families in our region and
nationwide. This topic has been highlighted in both the popular media and
Today, in conjunction with Dr. Williams we look to bring you up-to-date
information regarding the diagnosis and prevention of acute flaccid myelitis, its
association with certain viruses, and also how we're interfacing with the Centers
for Disease Control to assess the situation here in Western Pennsylvania.
Welcome, Dr. Williams.
Dr. Williams: Thanks, Brian. Thanks, Carolyn. Good to be here. I'm normally here as a host, as
regular listeners may know. It's a pleasure to be a guest.
Carolyn Coyne: Tables have turned.
Dr. Williams: Do I get two checks for this?
Carolyn Coyne: I think, yes. It's in the mail.
Brian Martin: Yes, yeah. Yeah, yeah.
Dr. Williams: Oh wait. That's right. We don't get paid for this.
Brian Martin: Thanks for reminding us.
Carolyn Coyne: John, maybe how we could start this is just to give a little background to the
listeners as to what we're seeing with these cases. Are they unusual? On your
side, of course, as being the division chief of Peds ID, when you first became
aware of this and where we're at now?
Dr. Williams: Sure. Acute flaccid myelitis or AFM, as I'm going to call it through most of the
podcast, is an acute neurologic disorder of childhood that usually has an onset
over a couple of days, and it presents as weakness usually of arms and legs. It's
often asymmetric or uneven. So it's often one side is affected more than the
other. That is really clinically how it presents. Children can have other symptoms
such as fever or respiratory or intestinal, but without that weakness of the arms
and legs it's not AFM. That's really the key feature that the child will have.
AFM has been known and occurs sporadically for a long time. In fact, we may
touch on this later, but 60 years ago before the polio vaccine, there were tens of
thousands of cases of severe AFM or paralytic polio myelitis every year in this
country. Since then, there are some cases but not that many. Starting about
four years ago in 2014, there was a large national outbreak and there were
about 150 cases. Again, in 2016, there were about 150 cases. 2015, 2017, there
were only a couple, a few dozen. This year so far, there look to be a lot of cases
as well. It's been noticed nationally over about the last month or so in many
places in the country that people are seeing a lot more cases like we did in 2016,
like we did in 2014.
Brian Martin: John, can you speak to outside the United States? Are you aware with your
infectious disease colleagues of speaking about the impact of AFM globally?
Dr. Williams: Yeah. AFM globally, until very recently, the last, say, 10 to 15 years the major
cause of AFM globally was polio. Anybody under the age of 55 has forgotten it in
this country, but it was still a major cause of severe AFM and paralysis
worldwide. Polio now, due to vaccine, is down to only a couple of countries. So
it's on its way to being eradicated. The other viruses that can be associated with
AFM are found in other countries in the world. Although in every country in the
world, it's pretty rare in childhood.
Carolyn Coyne: Well, then just to clarify that. You sort of immediately draw our attention to
viruses. So I'm curious as an ID doctor, a parent maybe brings a child into the
clinic or into the emergency room with AFM. What do you suspect initially is the
causative agent, and then what is your plan to diagnose it and to treat it? What
are the options?
Dr. Williams: That's a great question. Most cases of AFM that have been studied, and it's only
been more closely studied in these large outbreaks in 2014 and 2016 and now
2018. Most cases, a specific cause is not found. But of the causes that are found,
most of them are viruses. There's a number of different viruses that we'll
probably talk about. What we do is first ask the family any exposure the child
may have had or any recent illnesses. In terms of caring for the child, we don't
have medicines for most of these viruses. So the treatments we provide children
who come to the hospital with AFM are supportive care if they're having
problems with breathing or blood pressure or circulation or things like that.
If we think they have a lot of inflammation, if their immune system is very
activated, they might be treated with medicines to affect their immune system.
And then we do a lot of testing. We do blood testing to look for different
infections. We do spinal fluid testing to look for different infections. A key part
of it is an MRI, which is a special imaging technique of the brain that can reveal
patterns that can really tell you if the child has AFM or some other kind of nerve
Carolyn Coyne: We've been talking a lot about, obviously, children. Here we are at CHP, but
could you talk maybe a little bit about AFM in terms of who's afflicted by it?
Certainly we know that a lot of young children seem to be more sensitive and
why is that? At what age are children at greatest risk for this?
Dr. Williams: We know that about 90% of cases of AFM occur in people under the age of 18,
so most of the disease is in children. The mean age is about five to seven years
old, so it's mainly younger children. Why that is we don't really know. We think
that viruses are a common cause of AFM, and there are literally hundreds of
different viruses, common viruses, that children encounter during the course of
childhood. All of us encounter these viruses as a natural part of growing up and
building a healthy immune system. So it may be that children are encountering
some of these viruses for the first time.
There's also thought that it might have something to do with the fact that
children's immune systems may not be as fully developed as an adult. But the
truth is, we really don't know. There's much more we don't know about AFM
than what we do know.
Brian Martin: John, could you speak a little bit about other aspects of the differential
diagnosis? We have pediatricians and families that could be listening to the
podcast here. We've sort of honed in on viruses, but what other things do you
see that might present something like this that could worry a pediatrician or a
family that this could be a case of AFM? I really liked how at the beginning you
were very specific about that unilateral weakness being kind of a hallmark of
this to allow the clinician to make a really informed decision at the beginning of
the differential. But are there other things that look like this that clinicians could
be thinking about?
Dr. Williams: Yeah. I think that's a good point, Brian. That is a key thing is the weakness
because we've been talking about viruses and how common viruses are. Any of
us who have children or work in a children's hospital like this know how
commonly kids get runny noses and coughs and vomiting and diarrhea and
rashes. None of those things are AFM, so it really is the thing is for the parents
and the care provider to notice that there's weakness of one or more arms and
legs. And then in addition to AFM, which is a distinct kind of disease that causes
weakness, there are other diseases such as there some immune diseases where
the immune system actually attacks the central nervous system.
One of those that people have heard of perhaps in adults is called multiple
sclerosis. We rarely see that in children, but there are similar kinds of diseases
where there's no infection, but the immune system is attacking the nerves. We
would treat those differently than we might treat an infection. We don't see this
much in this country because we have clean water and a clean environment.
Yes, even here in Pittsburgh, former steel town, we have a very clean river. But
certain toxins or heavy metals can also cause a similar kind of weakness or
Carolyn Coyne: Maybe now we can transition to talking about the possible viral suspects. Of
course, you mentioned that a child comes in, you would run a panel of tests to
confirm that it's AFM. Now you want to figure out what it is. Maybe you could
talk about the most likely suspects and how you go about that diagnosis, and
maybe we could talk a little bit more about what it means, what those suspects
Dr. Williams: The major viruses we think of, and then I get to play host in a minute here. One
is a group of viruses called enteroviruses. Much less commonly in children in
most years and certainly in this year is a virus that's transmitted by mosquitoes
called West Nile virus. I would just note that the CDC said in the last day or two
that of the current cases that they are studying this year, none of them are due
to West Nile virus, but West Nile virus can cause an asymmetric paralysis. We
really don't see it in this country, so unless somebody has traveled it wouldn't
be relevant. But there's a virus called Japanese encephalitis virus that can cause
Polio, which I just mentioned, is now, thanks to the polio vaccine, only
circulating in a couple of countries in the world, the major two being Pakistan
and Afghanistan and Nigeria. And then rabies virus, which is extraordinarily rare
in humans. When a virus is found, the most common virus that's found is an
enterovirus. Carolyn, I happen to know since our labs are close to each other,
that you are a leading expert in enteroviruses. So maybe you could tell us about
Carolyn Coyne: Sure. Yeah. My lab has been studying enteroviruses for about 15 years now. I
started actually doing this when I was a postdoctoral fellow. I can tell you a little
bit about enteroviruses, maybe even the things that we do, but how it relates to
this. Enteroviruses are a very, very common cause of human infection. In fact,
they are listed by the CDC as the most common infectious viral agent of
humans. That's largely because it's a large family of viruses. As the name would
suggest, and I always like to remind people that you can impress your friends by
the names of viruses and how you can figure out what they are because an
enterovirus is an enteric virus, as the name would suggest.
These viruses are most commonly transmitted by what we refer to as the fecaloral route. So viruses of an infected individual are shed at usually very high
levels in the feces. Of course, you then become exposed to the virus during
initial transmission by potentially touching a contaminated surface with feces,
putting it to your mouth of course, eating, ingesting any food or certainly water
that's contaminated with that feces, and that's really the most common route of
transmission. With some of the viruses, they can actually also be transmitted by
the respiratory route. Much like we think about flu, let's say, these viruses can
also enter through our upper respiratory tracts as well.
It's a very, very large family of viruses. There are over 100 serotypes of these
viruses. You mentioned before polio virus. I think certainly that's the most
widely-known within the family. But what we know is there's a lot of other
members of the enterovirus family that cause severe disease primarily in
children. If you really look at the spread of the disease manifestations and the
severity of disease, mortality, morbidity, we certainly see this in children below
the age of one or two the most. And then there's another peak of complications
in the elderly, which as you referred to before, is really likely driven by the
immune system at both of those stages of life.
But there are over 100 different serotypes of enteroviruses, so we know polio
types. But some of the other more common ones that we think about are
Coxsackieviruses. This includes Coxsackievirus A or CVA. For any parents of
children in daycare or perhaps in elementary school, you probably know this
virus and hate this virus because it's really one of the more common causative
agents of hand-foot-and-mouth disease. Children, you can often see signs, I see
them all the time in my son's daycare when I pick him up, of Coxsackievirus.
Usually how that virus presents is, at the name would describe, you get blisters
and sores on your hands, your feet, and in your mouth.
There's other viruses in addition to Coxsackieviruses. There's enterovirus 71,
EV71. This is a virus that much like, I think, some of the other enteroviruses
have been associated with really widespread global outbreaks. In fact, in China
there was an outbreak between I think it was 2007 to 2012 where there were
over seven million cases of infection. For that virus, it's also associated with
hand-foot-and-mouth disease, but this is a virus that's also commonly
associated with AFM. So oftentimes the more common kind of symptoms are
hand-foot-and-mouth, it's also associated with acute flaccid paralysis.
In addition to that, there's lots of other viruses that are not as perhaps wellknown, and those include ECHO viruses, also that impact the young, as well as
another, I would say, more emerging enterovirus, which is called enterovirus
D68 or EV-D68. This is a virus that has really been associated with a lot of the
AFM cases certainly within the United States during these kind of peak
outbreaks that you mentioned, 2016. EV-D68 is a little bit unlike some of the
other enteroviruses just in the route of transmission. I mentioned before that
enteroviruses are primarily transmitted by the fecal-oral route. For EV-D68, it's a
little bit of an anomaly because it really seems to prefer, if you will, a
transmission through the respiratory route.
So it resembles a little bit more of what we think of as a rhinovirus or the
common cold virus, which actually is also officially within the enterovirus family.
EV-D68 though is also associated with very high rates of AFM and has been, I
would say, one of the common causes of these more recent outbreaks certainly
within the United States.
Dr. Williams: I think then, I mean that leads me to one point that you just touched on is about
the fact that these viruses are spread either by the fecal-oral route or by the
respiratory route. So in terms of prevention of infection, the classic
recommendations that our mothers all hopefully taught us which is to cough
and sneeze into your elbow and then hand hygiene with hand gel or soap and
Carolyn Coyne: The other thing that I would just note too is that these are very, very common
viruses. We have all had these viruses many times in our lives. Kids get these
viruses every year. It's actually a very, very rare outcome of these viruses to
develop AFM. I mean, this was the same for polio virus as well. Many cases of
infection with these viruses are completely asymptomatic within children,
within adults. You never know you've been infected. Certainly the most
common is just what you would think of as a mild cold or flu-like symptoms. You
would have a fever. You certainly wouldn't feel well. So it's a very, very actually
rare complication to have AFM.
Although these viruses are widespread and certainly exposure is quite common,
it certainly really should be noted that most individuals and most children
infected with these viruses will not go on to develop AFM.
Brian Martin: As the non-virologist, non-infectious disease specialist in the room, I did a little
back of the napkin math to give our ... our viewers, my goodness, our listenersCarolyn Coyne: Good thing they're not viewers.
Brian Martin: Yeah. Good thing. Good thing, yes. I have a face for radio. But to give our
listeners a little bit of perspective on that, in 2016 the census said there was
approximately 74 million children in the United States and we're talking
approximately 150 out of ... And those are children under 18, so 150 cases out
of 74 million gives us a little bit of perspective. I actually did the math, so in
terms of it's a .0002% incidence. It's a very rare event. I think that one of the
takeaways for me as a parent and as somebody that obviously has a lot of
people asking me questions about this, is that the vast majority, from what I'm
hearing from you, is the vast majority of enterovirus infection is self-limiting.
It's a hand-foot-and-mouth presentation where a child will have some fever,
might have a little bit of dysphagia for a time, not feel well, but will have a full
and complete recovery and that the basics, John, to your point, about
prevention here really revolves around the basics of what we would do for a
cold or a flu, which is essentially perform good hand hygiene and mind your
sneezes and other things that we do to help prevent respiratory illness.
Carolyn Coyne: Yeah, absolutely. Maybe what we could end on, and I'll throw this back to John
so we can put our hats back on where they were to begin with. Maybe just to
finish up, you could provide advice for parents who might be worried. Again, I'm
the parent of a young son and so I can appreciate this. Just to let people know
what symptoms to look for, and then when to potentially think there is cause
Dr. Williams: My kids are older now, but I get no less concerned about them than I did when
they were young. It is scary for parents when you hear about things like that. So
I think first we have to remember that this is very rare, as you just said, Brian.
It's less than one in a million. Before polio vaccine, there were over 15,000 cases
of paralysis a year in this country, before the polio vaccine, invented by Jonas
Salk here at University of Pittsburgh. So yay vaccines. Thank you.
The viruses are very common, as you said. So in terms of prevention, really it's
hand hygiene but letting kids be kids. They should still be going to daycare and
going to school because most of those million kids who get any of these viruses
are not going to have AFM. I think in terms of watching their children, it's really
watching for the sign of weakness, a child who's not using one of their arms to
feed themselves the way they should or not walking well or something like that.
If they just have respiratory symptoms or vomiting or diarrhea, that shouldn't
make the parent concerned that that child is going to have AFM.
One final point, because I think as parents and pediatricians we all think about
protecting our own kids and protecting other kids. Everybody is appropriately
concerned about a potentially very serious disease like AFM, of which we said
there were 150 cases in these peak years. Okay, so influenza, there are tens of
thousands of children hospitalized every year in the US and several hundred
children die of flu in the US. Almost all of those are unvaccinated. So in addition
to what we talked about, I think the most important thing any parent or care
provider can do for their children is to get a flu shot, and it's time right now.
Carolyn Coyne: Yes.
Brian Martin: That is a fantastic point, John, and I think a great thing to close on.
Carolyn Coyne: Thank you so much for joining us, John.
Brian Martin: Thanks very much for your time.
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