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In this special episode, learn all about measles, the most infectious human virus on the planet, and the recent outbreak in the U.S. Our two guests are Paul Duprex, PhD, director of Center for Vaccine Research at the University of Pittsburgh School of Medicine and John Williams, MD, chief of the Division of Pediatric Infectious Diseases at UPMC Children’s and fellow podcast host.
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Carolyn Coyne: This podcast is for information and educational purposes only and is not to be
considered medical advice for any particular patients. Clinicians must rely on
their own informed clinical judgements when making recommendations for
their patients. Patients in need of medical advice should consult their personal
From UPMC Children's Hospital of Pittsburgh, welcome to That's Pediatrics. I'm Carolyn Coyne, I'm a scientist in the Division of Pediatric Infectious Diseases.
Brian Martin: And I'm Brian Martin, I'm a Vice-President of Medical Affairs here at Children's.
Carolyn Coyne: And today we have a very special episode with two guests for the very first time
on That's Pediatrics history. First we have John Williams, who normally sits as
one of the hosts of That's Pediatrics. John is a Professor of Microbiology and
Molecular Genetics and is the Division Chief for my division, Pediatric Infectious
Diseases. Joining him is Paul Duprex, Paul's a Professor of Microbiology and
Molecular Genetics, he's the Director of the Center for Vaccine Research at the
University of Pittsburgh. Welcome and thank you for joining us.
So today, we actually have a special episode focused on measles. I feel like I've
kinda gone into a bit of time machine but here we are talking about measles and
measles outbreak throughout the nation and also in Pittsburgh. So why don't
you Paul, you're a basic scientist who studied measles for a long time, why don't
you tell us a little bit about measles virus.
Paul Duprex: So, what's interesting about measles is, it is the most infectious human virus on
the planet. It's highly, highly transmissible and the problem with a very highly
transmissible virus is, if we do not immunize a large number of people, then
there will be little pockets of people who are susceptible, who can get that
infection and if the virus is imported from somewhere outside of the country,
these little pockets can amplify the virus like wildfire. So that's what you need to
remember about measles. One thing, highly, highly transmissible alongside a
virus which is readily preventable because we have a super vaccine.
Carolyn Coyne: So when you it's the most infectious virus, if there one individual infected with
measles, how many other individuals could get measles?
Paul Duprex: So the funny technical term that we use, doesn't really matter but it's
interesting to know, is R0 and R naught means how many people from one cases
of measles are likely to be infected. Now, this is a bit of a number, which is not
an absolute number, but it's a real good way to understand how infectious a
virus is or actually a bacterium as well. So, for measles, one person infected with
the virus can infect between 12 and 18 people. And that in this part of the
Brian Martin: That's considerable.
Paul Duprex: It's highly, highly infectious virus. If you think about something like influenza,
much much lower R naught compared to measles. If you think of something like
Ebola, big outbreak of Ebola in the world and people are thinking about Ebola
coming to America again. Desperately, desperately untransmissible virus, it's
really quite hard to catch Ebola. Also, HIV. Not an easy virus to catch. Measles,
on the other hand, is so so transmissible that if you get these little pockets of
people, who have never been vaccinated, it's very very likely that it spreads
from one person to the next to the next to the next to the next to the next, and
then you've got 12 or 18 people infected.
Carolyn Coyne: So, what makes it so infectious?
Paul Duprex: So, it's very very infectious because it's evolutionary very very clever. Now
clever, viruses aren't clever because virus can't think so what do I mean by
clever? Well, it has adapted a wonderful way to get into a person to spread right
around the body of that person, catching a ride on the very cells that are
supposed to stop it infecting us, so these are cells of the immune system. So the
virus is very very lymphotropic. So it infects immune cells really efficiently, it
even turns on its own entry receptor so that it allows even more cells to be
infected and what it does, and this is another thing to remember about measles,
it's very very immunosuppressive. What do we mean by immunosuppressive,
just that it really really dampens down the immune system.
So many many kids, not maybe in this part of the world, but in other parts of the
world, the developing world, who have bacterial infections, co-infections with
bacteria, really can die because of pneumonia. So it goes in, it spreads right
around the body and then it has to get out. So how does it get out? Well, it has
the ability, in the immune cell, to come into close proximity with a cell in the
epithelium. Now, the epithelium is just the cells that enter face in the lungs
between the inside of your body and the outside of your body and the outside
of your body, of course, is covered in air. So the virus is able to enter the bottom
of these epithelial cells and then it hijacks the body so beautifully.
It goes from the bottom of the cells to the top of the cells and what's really nice
about the top of those cells is, they're full of beating cilia, so the cilia are
whipping around the moving mucus about and the virus does to the top of the
cells, where there isn't anything to hold it back. So, because it hasn't come in
using those cells, rather it's come in using cells that the immune system spread
right around the body and then got to the top of these ciliated cells, it's just
whipped out into the air very very efficiently and the other thing about measles
is, whenever it's been whipped out into the air so so efficiently, that is before
the typical rash, because whenever people think about measles, people think
about red spots. But this infectivity is being released into the air before you see
the red spots, that's the problem. You can transmit measles before you know
you have measles.
Brian Martin: That's very helpful to hear about that continue of the disease process. Dr.
Williams, question for you. Could you please share with our listeners some of
the questions, like I know that the Infectious Disease Department here at
Children's has been likely fielding a number of inquiries because measles is,
fortunately measles outbreak is a relatively rare event. We have concerns from
primary care physicians and from other providers across the care continuum.
Could you just share with us some of the questions that are coming in, both
from on the provider side and then also on the patient side if any of those a
John Williams: Yeah, we've been getting a lot of questions, Brian, both from pediatricians and
physicians in the community and other healthcare providers and families.
Unfortunately, measles outbreaks are not as rare as you might think and they're
becoming more common because of what Paul mentioned about the vaccines.
So, measles was declared eradicated in the United States in 2000. Twenty years
ago, okay, because we were vaccinating very effectively and, as Paul said, the
vaccine works terrifically well. Safe, highly effective. But because of concerns
about the vaccine, that have been shown in many large studies to be
unfounded, we're in the midst of another outbreak of measles.
So far this year, as of April 26th, we had 704 cases. Only in, not quite five
months, that's more than in any year in the United States since 1994 and we're
not even halfway through the year. So this is really, we've had recent outbreaks
in recent years that people have probably seen and read about but this has
been one of the worst. You know, knock on wood, this year there have not yet
been any deaths but 10 percent of those patients with measles have had to be
put in the hospital. 10 percent. So Paul mentioned, flu, influenza as a
comparison. Every year, 10 to 50 million people get flu, only about 1 percent of
them end up in the hospital. So the measles, it's really a very severe illness and
lots of these kids and adults get sick. So that's one of the questions we've had is,
how to treat these patients, how to approach them.
A very common question we get is about vaccines and if people have had their
routine vaccines on schedule, then they should be protected. There are some
exceptions if, for infants younger than 12 months, they might need an extra
dose of vaccine, if they have direct exposure. For adults, who were born
between 1957 and 1989, they probably only got one dose of vaccine and they
might need a second dose if they have direct exposure. For most of our children,
including all of my children, who had their dose at 12 or 15 months and then a
dose about four, five years, they're good, they're fully protected.
Carolyn Coyne: You often hear people say, “Well, in the old days, I got measles and it wasn't
that big of a deal”. You spoke a little bit about the complications of this and I'm
just wondering if you can talk in more detail about that. 10 percent of people
might get hospitalized but what are the more severe outcomes that can happen
if you get measles.
John Williams: I'll say a few words and then I have a question for Paul about that. Globally,
hundreds of thousands of children die of measles every year. It used to be
millions. The reason it's not millions anymore is because of the vaccine. Because
the vaccine is safe and highly effective. But when children die, they often die of
a secondary pneumonia, as Paul mentioned, the bacterial pneumonia. They can
get severe diarrhea and dehydration. So, most of the deaths is in the period
when they're acutely sick but I wondered Paul, you mentioned that the measles
suppresses the immune system. Is that just short-term of does that go on for a
Paul Duprex: So what goes on for quite some time after the infection and this is what people
call the measles' paradox because the paradox is, you get this phenomenal
immune suppression, you get all of these secondary infections, especially in the
developing world, which leads to the mortality due to measles. But you get this
lifelong immune protection. So people who have had measles, that's the one
group of people that they say don't need to be vaccinated again. If you've been
born before 1957, you most certainly will have had measles, even though you
might not know it. If we take some blood, and if we do some tests,
neutralization tests, other antibodies and map blood which knock down the
virus, they're still doing to be there. So, that's the paradox with measles. You get
this profound immune suppression, you get this wonderful lifelong immunity
and the problem with the immune suppression is that is leads to many
The other thing which is interesting about measles, and people don't know this
is, it's one of the leading causes of blindness in the developing world. It's a real
problem for kids longterm and the other thing which is important whenever
thinking about other complications of measles is the virus is lymphotropic,
infects the immune system, we talked about that already. It's epitheliotropic. It
can infects the epithelial cells but it's also neurotropic. So when rare instances,
the virus can cause encephalitis and that's what causes most of the
hospitalizations in the developed world where we live, are due to these central
nervous system complications and then there are other really really rare but
absolutely fascinating conditions, known as subacute sclerosing panencephalitis,
it's a hugely long name. But essentially what this is and something worth
remembering about is, whenever kids get infected, this was the received
wisdom. Whenever kids get infected really really young in life, the propensity
for this condition, SSPE, was much more likely to occur. What is SSPE? Well, it's
the longterm persistence of a human virus in a person.
So, we're used to DNA viruses lasting for a long time so we're used to DNA
viruses hanging around in cold sores but we're not typically used to RNA viruses
and that's sort of a technical thing, a little bit of a technical thing but we're not
used to viruses like measles hanging around so long in our bodies but what can
happen is, the virus, whenever it infects a very young kid, can lie dormant
somewhere, typically people say it's central nervous system but that's not been
proven and what happens is the virus reactivates whenever the kid is, on
average, about eight to ten years after that primary infection. How does that
manifest? Well in the first instance, there's the kid is maybe has some of the
fine motor, or the teenager has some fine motor skills are lost, but just let's say
somebody who is a little bit awkward. But after two years, the virus has
reactivated and spread so excessively in central nervous system that the
adolescent is in a coma and there is no cure, no one has survived this condition
Carolyn Coyne: Wow.
Paul Duprex: So you don't want to get measles as a very young kid, in fact, you don't want to
get measles at all. That's the worst case scenario but it's still not a nice disease.
John Williams: Well and I think, as Paul mentioned, there used to be millions of cases a year in
the U.S. as well as in developing nations because essentially measles is so
contagious, as Paul says, that everybody got it. Okay, so about one out of a
thousand children would have severe brain involvement that would often lead
to severe irreversible damage or death. The kind of things that Paul is talking
about and some people might think, well one of a thousand, those are pretty
low odds. Okay, there are four million kids a year born in this country, right? So
that's thousands and thousands of children, that that used to happen to and still
happens in developing nations and it doesn't happen now because of vaccine.
Carolyn Coyne: So what do you tell people right? So I mean, I can imagine there's a lot of people
certainly within our own city saying, oh my god, there's four or five cases of
measles, what do I do, should my child go to school, what should I look for,
should I be re-vaccinated, so what do you tell people who are scared because
they seen the news and they see that it's now in Pittsburgh.
John Williams: Well, I think, as a pediatrician, and somebody with kids, what we've been telling
people is, number one, get your routine vaccines. If everybody were all their
routine vaccines, including the measles vaccine, it wouldn't be an issue, as Paul
said, with a lot of population immune, you're okay. Currently, our city, many
schools and many people are good about getting vaccines. So, in terms of direct
risk of people right now, it's not very high because there are only a few cases
and, unless somebody has direct exposure to those cases, or it becomes more
widespread, then people are okay. I think there are guidelines, actually from the
CDC and posted on our website and that we have circulated to pediatricians
about who might consider getting either an extra dose of vaccine or vaccine
I think the common question people often have about that, and this touches
back to what Paul said before, about whether you're immune or not, should we,
in a children's hospital like this, should we ask our doctor to check and see if
we're immune or just get a vaccine. The answer is usually just, get a vaccine, it's
completely safe to have extra doses so I had individual measles vaccine in the
early 1960s before it was combined as the MMR and my parents were great at a
lot of things but keeping medical records, it turns out, was not one of them. So
later in life, I had to repeatedly keep getting MMR vaccines so I've had four
measles vaccines in my life. I'm fine but I know I'm well protected. I'm glad for
Paul Duprex: If you think about the vaccine, what I always have to say is, it's always always
safer to get the vaccine then it is to get the disease and that's just a matter of
trying to understand what the risks are. Nothing in life is without risk. Driving in
the car to get the vaccine is way way way more riskier than getting the vaccine
and getting the disease is not without risk as well. So that's what we have to try
and help people understand and it's difficult right, people don't easily weigh up
those risks, people are maybe afraid getting into an airplane but very happy to
drive to Giant Eagle and we weight that up as a society.
Brian Martin: We are poor assessors of routine. Humans are routinely poor assessors of risk,
Paul Duprex: And it's really difficult, it's difficult for people and you know, look at us right, we
are fortunate, we know what a virus is. We've been train and taught about
vaccines and we know what it is. So you have to also have sympathy and
understanding for people who are just trying to do the right thing for their kids
and then this is where the internet's great but the internet is very very
challenging because it's difficult for people to weigh up the evidence whenever
all the evidence on Google looks to be the same. So John already mentioned,
where do you get your advice? Well, you get your advice from CDC and you get
your advice from what's been posted on the UPMC Children's webpage rather
than some Hollywood celebrity, who might not really know how to spell virus.
That just seems to make sense. So we should understand risk and we also
should understand where we should get our information from.
Brian Martin: Can't put it more succinctly than that.
Carolyn Coyne: Talk to your pediatrician if questions.
Brian Martin: No question.
Carolyn Coyne: Well thank you both for joining us. That is informative and educational. Thank
Brian Martin: Thank you.
John Williams: Thanks for having us.
Paul Duprex: Thank you.
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