Pneumonia
Pneumonia is an inflammation of the lungs, usually caused by an infection. It is very common worldwide, mostly in people over 65. Most types of pneumonia can usually be treated effectively with antibiotics. However it can also be a serious illness, especially for people who are frail or already ill.
Causes and risk factors
Pneumonia is usually caused by infection of the lung tissue by one of many different microorganisms (germs). These may be present in the body for some time before causing illness.
Pneumonia can also be caused by inhaling substances, such as caustic chemicals, food or vomit into the lungs. This is known as "aspiration" pneumonia.
The very young and very old are most susceptible to pneumonia. Smoking, heavy drinking, heart failure, diabetes, or having a lung disease, such as chronic obstructive pulmonary disease (COPD), also increases the risk of developing pneumonia. Pneumonia is also more likely to develop after another illness such as flu.
Symptoms
With the most common type of pneumonia, symptoms may come on quite suddenly. There may be pain in the side of the chest that can make breathing and coughing uncomfortable. This is due to the inflammation of the air sacs (alveolar sacs) and narrowing of the fine tubes in the lungs (bronchioles) caused by the infection.
The cough might be dry at the beginning of the illness but then tends to be productive, with phlegm that is often green/yellow or rust-coloured and may be smelly. Pneumonia also makes you feel ill, with fever, aches and pains, and loss of appetite. The exact symptoms vary depending on how much of the lung is affected and the type of infection responsible.
A straightforward case of pneumonia will begin to improve quickly with treatment and generally causes no long-term harm to the lungs. Complications, which are more common in older people, can include a build up of pus in the lungs (pleural effusion) and breathing difficulties, which will need treatment in hospital.
Types of pneumonia
Pneumonia can be divided into two main types, depending on whether the person affected caught it while living at home (in the community) or while staying in hospital.
Community-acquired pneumonia
Especially in adults up to middle age, community-acquired pneumonia is often a relatively mild illness.
The most common infection responsible is the bacteria Streptococcus pneumoniae. The illness is known as pneumococcal pneumonia. Other bacteria that cause pneumonia include Haemophilus influenzae. These more common bacterial causes are referred to as "typical pneumonia". In children and young adults, the bacteria Microplasma pneumoniae may be responsible.
All of these infections are spread from person to person through droplets in the air. Coughing and sneezing, which create droplets, makes the spread more effective.
Viruses including flu, herpes, measles and chickenpox can cause pneumonia. An infection with a bacterium can occur at the same time. It is then known as a secondary infection and can slow down recovery significantly.
Less commonly, other microorganisms can cause other forms of pneumonia. These illnesses are classed as "atypical pneumonia". This includes legionnaire´s disease, caused by a bacterium, and SARS (severe acute respiratory syndrome) caused by a virus.
Hospital-acquired pneumonia
People in hospital are vulnerable to pneumonia for a number of reasons. In comparison with people not in hospital, they are more likely to have a weakened immune system. And if they have had surgery or are very poorly, they may have a reduced cough reflex (one of the body´s defences against infections).
The types of bacteria responsible for pneumonia caught in hospital tend to be different from those that cause community-acquired pneumonia. These include the bacterium Staphylococcus aureus.
Weakened immune system
Pneumonia is more likely in people who have a damaged or suppressed immune system. This includes people who have AIDS and those who need to take steroid tablets or who are having some types of chemotherapy.
In people with a weakened immune system, there are additional pneumonia-causing infections, including one caused by the fungus-like organism Pneumocystis carinii. This infection is only rarely the cause of pneumonia in people who have a fully-functioning immune system. A long-term, daily dose of preventive antibiotics may be given for people with a weakened immune system.
Diagnosing pneumonia
A doctor can often diagnose pneumonia from hearing the patient´s account of the symptoms and by performing a physical examination. This examination includes "tapping" on the chest and listening to the breath sounds with a stethoscope. It helps the doctor to determine the location and extent of the infection. He or she might request a chest X-ray to help confirm the diagnosis. The doctor may also take a sample of blood for testing.
The next stage is to decide which treatment to take. For bacterial infections, antibiotics are generally very effective. However, the choice of which antibiotic you will need to take depends on which germ is causing the infection.
To establish this, the doctor may take a sample of phlegm and send it for laboratory examination. The laboratory can then do tests to find out which organism is present, and which antibiotics work to treat it.
This testing process is particularly important for pneumonia acquired in hospital because many bacteria there are becoming resistant to the commonly-used antibiotics.
In the community, antibiotics will be prescribed immediately, before any test results are obtained. This is because it is usually safe to assume that the infection will respond to standard antibiotics such as amoxicillin.
Treating pneumonia
Pneumonia caused by bacteria is treated with antibiotics which will need to be taken for 7-21 days, depending on which type of infection is suspected.
If the illness is severe, and especially in very young and old people, the pneumonia may need to be treated in hospital. For bacterial pneumonia, antibiotics and fluids can be given into a vein (intravenously). To help with breathing, extra oxygen can be provided through a face mask. For fungal pneumonia, antifungal drugs taken as tablets or intravenously may be given.
Viruses cannot be treated with antibiotics. However, antibiotic treatment may be needed for a secondary bacterial infection. For infections caused by the chickenpox or herpes viruses, antiviral drugs may be prescribed if the infection is caught early.
Prevention
Stopping smoking and only drinking in moderation can reduce your risk of many illnesses, including pneumonia.
There are immunisations for several of the infections that can cause pneumonia. These include Haemophilus influnzae type B vaccine - the "Hib" vaccine now given routinely to babies - and flu. Everybody over age 65, and those with long-term lung, heart or kidney diseases, or with a weakened immune system, should have the annual flu vaccination, available from GP surgeries each autumn.