Respiratory Tract Infections: Classification

00:00 When we're talking about lung infections, we define the infection by the site.

00:05 So that means that if you have an infection of the pharynx, or the nose, or the larynx, that's called an upper respiratory tract infection.

00:13 And that's usually the common cold or viral infection that we've all had repeatedly in our lives.

00:18 There are the occasional rare diseases caused by bacteria, which we'll mention later diphtheria / epiglottitis, for example.

00:25 Then in the lower respiratory tract, you may get infections, which only affect the trachea, or the bronchial tree.

00:32 Now, they tend to be that you will get an infection of the trachea and it will spread to the bronchi.

00:37 They're not independent of each other.

00:39 Usually you get a tracheobronchitis.

00:42 And again, that's often a viral infection.

00:44 And again, we've probably all had those several times in our lives.

00:48 That's the acute infection of the bronchial tree.

00:51 Chronic bronchial infection is largely a disease called bronchiectasis.

00:55 And that's a subject I wanted to talks on airways disease.

00:59 The main subject of this lecture is pneumonia.

01:02 And that is an infection that's affecting the alveoli.

01:06 And it's an acute infection.

01:09 There are a range of less acute infections of the alveoli.

01:13 Tuberculosis being the most common.

01:15 Other things will be lung abscess, and some very rare infections due to fungi and unusual bacteria.

01:21 And those are mentioned and discussed in the talk in tuberculosis.

01:26 So today, we really concentrate on acute pneumonia alveolar infection, and it could be due to a virus, or it could be due to bacteria.

01:35 So, pneumonia is incredibly common.

01:38 It affects about one in 200 people each year and it is actually the commonest cause of death in children under the age of five across the developing world.

01:46 As I've already mentioned, the pneumococcus streptococcus pneumoniae is the commonest cause.

01:53 Before we discussed pneumonia, I'm just briefly going to cover upper respiratory tract infections.

01:59 These are incredibly common.

02:00 As I've mentioned, we all have had colds in our life and will get repeated colds as time goes by.

02:05 These are mainly due to viruses. Rhinovirus, Adenovirus various influenza viruses, Metapneumovirus, etc.

02:12 And occasionally they can be due to a bacterium the common is been streptococcus pyogenes, which causes the disease, that everyone calls strep throat.

02:19 And that's basically a bacterial infection of the pharynx.

02:22 Patients with upper respiratory tract infections presents similarly an independent of what the pathogen is was sneezing, a sore throat, cough, mild systemic upset, a bit of a fever, feeling unwell, wanting to go to bed.

02:35 And the treatment actually is not much.

02:37 We just leave this, and people will get better most of the time.

02:41 If you have a strep pyogenes pharyngitis then actually antibiotics would be helpful, and penicillin will be beneficial in those circumstances.

02:50 There are a couple of bacterial infection the upper respiratory tract which are very important because they are potentially dangerous.

02:57 Diptheria is a laryngitis.

02:59 An infection of the larynx caused by a bacterium called Corynebacterium diphtheriae.

03:04 The important thing about diphtheria is that the infection forms what we call a pseudomembrane.

03:09 As an extra layer of gunky tissue on the surface of the larynx, And that pseudomembrane causes obstruction of the larynx.

03:18 And of course, the larynx is a relatively small surface area, and is where all the air that goes into your lungs has to pass through.

03:24 And that causes airways obstruction, and therefore is potentially dangerous, and which is why diphtheria used to be a very common cause of death in infants.

03:34 Epiglottitis is a rare infection of the epiglottis, as his name suggests, and that's due to a bacteria called haemophilus influenzae.

03:42 And again, it causes swelling of the epiglottis and therefore cause upper airways obstruction and is potentially dangerous as a consequence of that.

03:49 Fortunately, diphtheria can be vaccinated against and has become much less of a problem than it used to be in the past.

03:57 So, if we talk about lower respiratory tract infections, those that occur below the larynx, affecting the trachea, the bronchi, or the alveoli.

04:04 In fact, most patients lower speech transfection will have the tracheobronchitis that we mentioned.

04:09 That's the bottom part of this pyramid of infection.

04:11 And only a small portion of patients actually go on to divert the more serious form of lower respiratory tract infection, which is the pneumonia.

04:19 And of those with pneumonia, say about 100 people pneumonia, about 70% can be treated successfully in the community.

04:26 You don't need to get into hospital if you have pneumonia, because most cases is relatively mild.

04:31 However, in some people is a more severe disease.

04:34 And in some people is very severe disease, and they end up in hospital potentially in intensive care.

04:39 And there is a mortality which probably overall for each 100 people pneumonia, about three will die.