In this lecture, we’re going
to talk about bronchiolitis,
which is a viral infection of
the lower airways of a child.
So we in pediatrics see
this almost every day.
This is the number one cause of
hospitalization in the United States.
A child, perhaps
16 months of age,
and the parents noted that today he’s
had increased work of breathing.
You noticed some wheezing on exam,
he has a copious runny nose,
he’s been having fever,
and he’s had decreased oral intake
for about the last two days.
What’s your medical diagnosis?
It’s probably bronchiolitis.
So bronchiolitis is the
inflammation of the bronchioles,
which are the smallest air
passages of the lungs.
This narrowing of the airways
as a result of accrual of mucus
is what causes children to
develop respiratory distress.
Children have weaker
so it’s harder for them to clear the
mucus out of their lower airways.
At its peak, RSV accounts for
about a third of bronchiolitis
so we frequently think of RSV
when we think of bronchiolitis.
And as you can see here,
RSV is much more popular in the winter
months than in the summer months.
This may be because children are
more likely to be in enclosed areas
where they can share viruses,
but because there are other viruses
that happen at other times of the year,
it’s not entirely clear why we have
this seasonal variation of RSV.
So, other than RSV, what
else causes bronchiolitis?
Well, influenza could certainly
Rhinovirus can actually cause
fairly severe bronchiolitis.
The parainfluenza virus is what we
normally think is causing croup,
but also can cause bronchiolitis,
as can adenovirus.
Children with adenovirus
can be very, very sick.
Human metapneumovirus is a
relatively new comer on the stage,
which we didn’t know about
much before the mid-1980s.
Bocavirus maybe causes bronchiolitis
or maybe it’s a virus
we’ve just found in our studies
that goes along for the ride.
There may be Middle Eastern
respiratory syndrome virus
or severe and acute
respiratory syndrome virus.
There are lots of viruses out there
and probably thousands we
don’t even know about.
And each virus has its own season.
So here, you can see the
familiar green line of RSV,
but also you can see
that the red line of
parainfluenza is happening
a little bit earlier
and some of the other viruses are sort
of just lingering along all year long.
So all of that together, we do
typically see the bronchiolitis season
starting around October
and ending around May,
with the summer seeing less but
absolutely not zero bronchiolitis.
There is one state, Florida, where
they have RSV almost year-round
and nobody knows why.
So does it matter though what
virus is causing bronchiolitis?
The fact is rapid viral panels are somewhat
expensive depending on where you are
and knowing the virus doesn’t seem to really
matter in terms of your plan of care.
As a result, the AAP recommends not
screening for types of viruses.
Chances are the American hospital
where you’re working is screening
and that is against the recommendations
of the American Academy of Pediatrics
and this is because knowing does not
affect the management of the patient.
We’re going to base our management of
the patient on how sick the patient is,
not which kind of
virus they have.
Some viruses may cause generally
worse disease, like RSV,
but we’ll treat them based on what
their severity of illness is,
not based on the virus.
So what puts kids at
risk for bronchiolitis?
There are a number of things that
are known to be risk factors,
although it’s not
entirely clear why.
So, socioeconomic status does
play into risk for bronchiolitis.
Mothers who didn’t study past
high school are more likely
to have children admitted
Crowding in the home,
two or more children to a bedroom
increases risk of bronchiolitis.
Having school-age siblings increases
the risk of bronchiolitis.
Breastfeeding is protective.
This is because the mother
may have the virus, as well,
and extrude antibodies against
that virus in her breastmilk,
which then protects the infant
who is eating the breastmilk.
So failing to breastfeed is
a risk factor independently
for a child being hospitalized
Passive smoke exposure is a
risk factor for bronchiolitis.
Children who have a particulate
environment are more
likely to have problems
with their lung function
and are more likely to be hospitalized when
they get that inevitable viral infection.
Attendance in daycare is a risk factor
because if you’re around
children with viruses,
well, you’re more
likely to get one.
And the last point seems fairly obvious,
since younger children are more
likely to get severe bronchiolitis,
if you’re born early in the year
and you’re less than six months old at the
start of the season of bronchiolitis,
you’re more likely to be hospitalized
simply because you are younger
during the outbreak
of the illness.