In our discussion of upper
respiratory tract infections,
there’s probably none more
important than acute pharyngitis.
So I will speak to you about that.
First, let’s define it.
Acute pharyngitis would be
inflammation of the pharynx
from multiple infections and noninfectious
causes characterized by this triad:
fever, sore throat, and
In terms of the epidemiology, this
is a very, very common problem
in the course of a year.
Almost 50% of children will
have an episode of pharyngitis
and almost 20% of adults have
pharyngitis in the course of one year.
Most of the patients who have it are
between the ages of 5 and 24.
And in temperate climates, we find
most of the pharyngitis when people
tend to be indoors
winter and early spring.
And this is a very unfortunate fact
that when patients go to the doctor
with complaints of pharyngitis,
they get antibiotics far too often.
Antibiotics are not
necessary in many cases.
So what are the key elements of how these
various pathogens cause sore throat?
The exact mechanisms actually
causing the symptoms and signs
are not fully understood.
There’s been some evidence that
act on sensory nerve endings,
but that’s not absolutely clear.
The organism that’s been
studied most extensively
and we’ll talk most extensively
about is group A streptococcus.
But actually, most
sore throats are viral
and can be caused by common cold
viruses, like the coronavirus,
but also, influenza virus, coxsackie,
or Epstein-Barr virus notorious for
causing infectious mononucleosis.
And here I’m showing you a picture of
group A streptococcal pharyngitis,
but more about that later.
Let’s talk about the pathogenesis
of pharyngitis caused
by group A strep.
This organism is notorious, it
has multiple virulence factors,
probably the most important
of which is M protein.
It’s also got a hyaluronic capsule.
And the group A strep is able to adhere
to epithelial cells of the pharynx
through things that most
people refer to as fimbriae.
Some scientists call them pili,
and in these fimbriae are fibronectin-binding
proteins and lipoteichoic acid,
and that’s how group A strep adheres
primarily to the epithelium.
And once it adheres, it’s able to
spread through pharyngeal tissue
through enzymes that can destroy tissue,
like hyaluronidase, streptokinase,
DNAses, and a variety
So this is really quite
a virulent organism.
But back to what I said earlier,
most causes of pharyngitis are
viral, 25% to 40% as a minimum,
and these include adenovirus,
rhinovirus another common cold virus,
enterovirus, and we can’t
forget influenza A and B.
But usually, influenza is a much more
serious and troublesome infection.
So they may have pharyngitis, but
they’re usually sick in many other ways
and other viruses can cause it.
Of course, group A strep is an important
cause because we have treatment for that
and it occurs in about
10% to 15% of adults,
which means that when an
adult gets a sore throat,
only about 10% to 15% of the
time is it due to group A strep.
On the other hand, when
kids get a sore throat,
we’re pushing almost a third of them
have group A strep as the cause.
Anaerobes can also cause pharyngitis,
particularly notorious is
We’ll have more to say about that later.
And then there are some others that
physicians must at least consider,
such as Corynebacterium diphtheriae,
but most people are immunized in developing
countries against that organism.
And we certainly need to
take a good sexual history
because occasionally Neisseria
gonorrhoeae can cause pharyngitis.
Mycoplasma pneumoniae can cause it among
young adults particularly college age
people who live in dormitory settings or
in the military barracks type settings.
And then among older folks, Chlamydophila
pneumoniae is a cause of pharyngitis.