Literal definition of pneumonia is the combination of an acute respiratory illness - and when
I say acute, I mean short lived. In other words, the patient was well up until a few
days ago and then developed a classic range of symptoms, which include fever, generally
feeling unwell, they may appreciate some pleurisy, they'll have a cough. They may be coughing
up phlegm, which is often a purulent or yellow.
And these symptoms in combination with a chest x-ray which shows new shadowing
that wasn't previously known about or that doesn't have an alternative or known cause,
in those circumstances we would make the diagnosis of pneumonia.
Pneumonia can be classified in a number of different ways.
Firstly, you can consider where the patient contracted the infection.
And then in that context you would classify the patient was having either
a community acquired pneumonia or a hospital acquired pneumonia.
Another way of considering pneumonia is to think about the type of organisms, which
can be the bacteria, viruses, or fungi that are the responsible for pneumonia.
You can also classify the pneumonia in terms of its severity. So not thinking about the organism
as such or even where the patient contracted the infection, but just looking at the consequence
of infection in the patient and make a decision as to how serious the illness is that the patient has.
And in the majority of people, pneumonia can be a relatively mild illness,
but as in many cases in medicine, patients can present with a spectrum of severity
from the mild to the life-threatening.
To answer the question what causes pneumonia,
I think it's helpful to separate that out into two parts. Firstly, think about
the potential organism that the patient's contracted that's causing the illness.
And then secondly, think of it at the level of the lung.
So, dealing with the first area, the most common causes of pneumonia are
organisms that come from either a virus, bacteria, or more rarely fungal infections.
Dealing with the second area which is at the lung and airway level, I think
patients and perhaps even some doctors get confused about one what actually pneumonia is, and
if asked the question: "how does pneumonia different for example from bronchitis?"
I think it's useful to think of it in this way, that bronchitis is in effect inflammation of the airway lining
and it can cause a cough and breathlessness and phlegm production and fever
and you can feel unwell with it.
However, pneumonia is different. Pneumonia is where the air sacks fill up with fluid,
so the lung becomes consolidated or solid. And that's what you can see on the chest x ray.
So you get all those symptoms, but the distinguishing feature
is that the air sacks fill up with inflammatory debris and fluid.
And it's a more serious infection, an infection that can lead to more serious consequences.
So we always take it very seriously.
To answer that question: "Is pneumonia contagious?"
I think the simple and very short answer is yes. It is an infection which is reliant upon
host to host transmission. And therefore, to be successful and to continue,
it needs to be passed on from one person to another.
However, the relative ease with which infection is passed from individual to individual
can vary depending on the organism. But they all rely on this capacity to spread.
The simple analogy is - and I'm sure many of us have seen the slow motion photography,
watching somebody sneeze, and the velocity of the micro droplets that emanate
out from the patient when that happens, if you can imagine that some of those micro droplets
will contain bacteria or virus, then you can see how easily it might be that sharing a living space
with somebody that has an infection of this type,
how easy it is to either touch a surface which has the organism on it,
or even to inhale micro droplets directly in the air.
And in this way infection spreads from one person to another.
It's true to say that majority of patients that develop a lower respiratory tract infection
which is in fact a pneumonia, often don't get diagnosed as such and will contact a GP
and complain of the common symptoms of breathlessness, cough, fever, mucky phlegm,
sometimes pleurisy.
And the GP will make a clinical assessment and provide a course of antibiotics.
And for the majority of these patients, that is absolutely the right approach to take.
If the patient is sick enough to warrant hospital admission and that decision is
often made or usually made by the GP, then in these circumstances
our approach is very different. We take a whole system approach
they have a formal assessment which includes the history, clinical history
where we talk to the patient, understand the sequence of events that led up to that day.
We examine the patient and we rearrange for a variety of tests. Firstly, imaging test
to confirm pneumonia, and then secondly, a variety of blood tests and sputum tests
to assess the severity of the illness, its impact on other organ systems, and try to
identify the cause of organism. If we believe the patient has a viral cause, the test, the
kits that we use will allow us to pinpoint exactly what virus. So, it may be one of the
subtypes of influenza for example, then we will consider anti-influenza medication
in the form of Tamiflu for example.
If, however, we believe it to be a bacterial infection, then the approach
of treatment would be primarily antibiotics. And the type of antibiotic would be in part
determined by the severity of illness and in part determined by what information we
have initially as to the potential cause.