Pneumonia Dr Trisha Macnair Thanks to modern antibiotics, many people, young and old, make a good recovery from pneumonia, but it's still a common cause of death among those who are seriously ill.

In this article

What causes it? What is atypical pneumonia?

Who's affected? What are the symptoms?

How's it diagnosed? What's the treatment?

Pneumonia means inflammation of the lungs and is usually caused by an infection. Many different bacteria, viruses and fungi can cause it.

Bacterial pneumonia is the most common form of pneumonia in adults and is usually more serious. It may be a secondary complication of a viral respiratory illness such as flu, especially in people with immune deficiencies.

One of the most common bacterial causes is Streptococcus pneumoniae. Other common causes include haemophilus and staphylococcus. More unusual bacteria are sometimes found, especially in people with underlying problems with their immune systems.

Respiratory viruses are the most common cause of pneumonia in young children up to school age.

Fungal pneumonia is almost always linked to an immunodeficiency.

Inhalation pneumonia is due to inhalation of foreign material, such as food or vomit.

Some types of pneumonia are known as atypical. These include infections caused by certain bacteria, such as Legionella pneumophila, Mycoplasma pneumoniae and Chlamydia pneumoniae.

Some atpycial pneumonias are milder, with a more gradual onset and less severe symptoms than might be expected from the x-ray. Others, such as legionella, have a high mortality.

Mycoplasma pneumonia is a common in children and may be associated with non-respiratory problems, such as rashes, anaemia or meningitis.

Older people are at particular risk of pneumonia. In younger people there's usually, but not always, a factor that increases their risk, such as smoking, heavy drinking, chronic lung disease or an underlying illness.

Common symptoms of pneumonia include:

• Sudden onset of high fever
• Chills and sweating
• Rapid shallow breathing
• Shortness of breath
• Sharp stabbing chest pains, especially on coughing or deep breaths
• Cough producing unpleasant sputum, which may be green, rusty or blood stained
• Confusion
• Muscle pain
• Headache
• Nausea and vomiting
• Diarrhoea

Symptoms vary depending on the cause. In older people, symptoms may be vague - their temperature may be only slightly raised or even normal, for example. Confusion may be the only clue something is wrong.

A prompt diagnosis of pneumonia is vital and involves tests such as chest x-rays and examination of sputum in the laboratory to identify the micro-organism causing the illness.

Bacterial pneumonia can be treated with antibiotics. Although antibiotics aren't effective against viral pneumonia, they may be given initially until the cause is confirmed.

Oxygen may be needed to help breathing, and an intravenous drip may be used to give fluids if the person is dehydrated.

Other treatments include physiotherapy.

Sometimes pneumonia can be treated at home with a combination of antibiotics, rest, plenty of fluids and paracetamol, ibuprofen or aspirin (children under 16 shouldn't be given aspirin).

Without treatment, mortality from bacterial pneumonia may be as high as 40 per cent. Among older people, mortality may be higher than this even when effective treatment is given.

Complications such as lung abscesses can follow pneumonia, so always seek further help if someone who appeared to be recovering relapses.

Vaccines are available to prevent some types of pneumonia. Pneumococcal vaccine prevents S. pneumoniae and HiB prevents pneumonia in children caused by H. influenzae type B. The influenza vaccine prevents flu and infections such as pneumonia that can complicate it.

This article was last medically reviewed by Dr Rob Hicks in January 2007.