Acute Pharyngitis: Definition and Epidemiology

00:02 In our discussion of upper respiratory tract infections, there’s probably none more important than acute pharyngitis.

00:09 So I will speak to you about that.

00:12 First, let’s define it.

00:15 Acute pharyngitis would be inflammation of the pharynx from multiple infections and noninfectious causes characterized by this triad: fever, sore throat, and pharyngeal inflammation.

00:34 In terms of the epidemiology, this is a very, very common problem in the course of a year.

00:42 Almost 50% of children will have an episode of pharyngitis and almost 20% of adults have pharyngitis in the course of one year.

00:55 Most of the patients who have it are between the ages of 5 and 24.

01:01 And in temperate climates, we find most of the pharyngitis when people tend to be indoors winter and early spring.

01:11 And this is a very unfortunate fact that when patients go to the doctor with complaints of pharyngitis, they get antibiotics far too often.

01:25 Antibiotics are not necessary in many cases.

01:32 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.

01:47 There’s been some evidence that bradykinin, prostaglandins act on sensory nerve endings, but that’s not absolutely clear.

01:58 The organism that’s been studied most extensively and we’ll talk most extensively about is group A streptococcus.

02:07 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.

02:25 And here I’m showing you a picture of group A streptococcal pharyngitis, but more about that later.

02:33 Let’s talk about the pathogenesis of pharyngitis caused by group A strep.

02:39 This organism is notorious, it has multiple virulence factors, probably the most important of which is M protein.

02:48 It’s also got a hyaluronic capsule.

02:52 And the group A strep is able to adhere to epithelial cells of the pharynx through things that most people refer to as fimbriae.

03:02 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.

03:21 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 of exotoxins.

03:37 So this is really quite a virulent organism.

03:42 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.

04:03 But usually, influenza is a much more serious and troublesome infection.

04:11 So they may have pharyngitis, but they’re usually sick in many other ways and other viruses can cause it.

04:20 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.

04:41 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.

04:51 Anaerobes can also cause pharyngitis, particularly notorious is Fusobacterium necrophorum.

04:59 We’ll have more to say about that later.

05:03 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.

05:17 And we certainly need to take a good sexual history because occasionally Neisseria gonorrhoeae can cause pharyngitis.

05:27 Mycoplasma pneumoniae can cause it among young adults particularly college age people who live in dormitory settings or in the military barracks type settings.

05:39 And then among older folks, Chlamydophila pneumoniae is a cause of pharyngitis.