00:00
So, pneumonia is classified into different types.
00:04
The first -- the most important and the subject of most of this talk today is community acquired pneumonia.
00:11
And that is what it says in its name is a pneumonia that is acquired
when you're living at home and not in hospital or anything else.
00:18
So it's the normal standard pneumonia that you pick up in your everyday life.
00:23
The other important forms of pneumonia are hospital acquired
which as it says is a pneumonia that you develop when you're in hospital.
00:31
So you're admitted to hospital for another reason, say you're having an operation
and then after the operation you develop a pneumonia.
00:38
That will be a hospital acquired pneumonia.
00:40
A third form of pneumonia is ventilator acquired.
00:43
That's basically a subtype of hospital acquired pneumonia.
00:46
But it means this is pneumonia in patients
who are on intensive care unit being ventilated.
00:52
And they are susceptible to pneumonia because the ET tube,
the endotracheal tube bypasses quite a lot of the normal immune mechanisms preventing infection.
01:02
And the last category, the immunocompromised host.
01:05
These are patients who have a very severe defect to their immune system
and that allows a range of unusual organisms, bacteria, viruses and fungi
to cause the pneumonia so the chance of having a pneumonia
through unusual is much higher in these patients.
01:24
But we're talking about patients who have severe immunocompromised state.
01:27
So those who've had chemotherapy for cancer, those with HIV infection, with poor CD4 counts,
those who had transplantation with their marrow or their kidney or their lung, etc.
01:38
So patients really with very severe immune defects.
01:42
So, who gets pneumonia? Well, there's an easy answer for that question.
01:46
That is absolutely everybody could get pneumonia. It's not uncommon in young people.
01:50
But, it is particularly common in two age groups. The very young, the under-fives.
01:55
And as I mentioned before, it's the commonest cause of death
across the developing world in the under-fives and the elderly.
02:03
And there's an almost exponential increase in the chance of developing pneumonia after the age of 65.
02:08
So, it ends up that the chance of developing pneumonia
in somebody who's very old over 85 is about 5% a year.
02:16
The risk factors for pneumonia also as well as age include previous influenza or other viral infections.
02:23
Because as I mentioned in the influenza lecture,
a viral infection of the respiratory tract affects the immune response to bacteria
and allows bacterial infections to develop as a consequence of the viral infection.
02:35
So secondary bacterial pneumonias after influenza are very common.
02:39
And that's the major way by which death is caused during the pandemics or has been in the past.
02:45
For example the post-World War I pandemic which killed 20 million people.
02:48
Most people died of pneumococcal and Staphylococcus pneumonia
after having the influenza virus infection.
02:55
Other people who are more susceptible to pneumonia are alcoholics
or people with liver cirrhosis cuz that affects the ability of the immune system to fight bacteria.
03:05
Smokers, allows the bacteria to establish infection in the lungs more readily.
03:09
Actually having had one episode of pneumonia
makes you two or three times more likely to have another episode.
03:15
It marks you out as somebody who's susceptible to pneumonia.
03:17
And then patients with chronic disease, chronic lung disease, COPD
for example, chronic neurological disease, dementia, previous stroke, etc.
03:26
Any renal impairment or cardiac failure.
03:30
These are all reasons why -- these all increase the chance of getting community acquired pneumonia.
03:35
Now, if you have hospital acquired pneumonia, you need to be in hospitals.
03:40
So if you're hospitalized for a reason, then you're at risk of hospital acquired pneumonia.
03:44
And if you're ventilated, then you're at risk of ventilator acquired pneumonia.
03:48
And the risk of that is about 1% per day that you are ventilated.
03:51
And then of course the patients who have immunosuppressed for their treatment for their cancer
or because they've had a lung transplantation, etc.
04:01
Those will be at risk of pneumonia of the immunosuppressed patient.