What is pneumonia?

Pneumonia is an inflammation of the lungs caused by bacteria, viruses, fungi and other microorganisms. They cause the small air sacs in the lungs to become filled with fluid produced by inflamed tissue.

Very young and very old people have weaker lung defences, so pneumonia is more common early and late in life. Viral pneumonias are usually mild, but they can be life-threatening in very old and very young patients, and in people whose immune systems are weak.

Legionnaires’ disease is a type of pneumonia caused by germs that thrive in very warm water. The germs that cause psittacosis are usually caught from birds, especially parrots. MRSA is often found in hospitals and can cause pneumonia in people who are admitted to hospital for other reasons.
The severity of pneumonia depends on which organism is causing the infection.
Common symptoms of pneumonia include cough, shortness of breath, fever and malaise.

What causes pneumonia?

Bacteria (in particular pneumococci) represent the leading cause of pneumonia.
Viral pneumonia can be caused by a range of viruses, including those that are responsible for the common cold and severe acute respiratory syndrome (SARS), the recent outbreak of which became a global health concern.

Community-acquired pneumonia (CAP) is that acquired outside hospital while nosocomial pneumonia (NP) is acquired while in hospital. For most countries, studies are not available on the causes of community-acquired pneumonia (CAP). However, more than 10 different microbial causes of CAP have been recognised. Limited information is available on the causes of nosocomial pneumonia (NP). However, the pathogenic agents that cause NP appear to differ between early-onset NP (that occurs within 4 days of hospitalisation) and late-onset NP (occurring after 4 days).

Bacteria causing CAP are increasingly resistant to commonly used antibiotics in most European countries. Multidrug resistance is also increasingly common in NP.

Smoking is the single most important identified preventable risk factor for Community Acquired Pneumonia (CAP). Increasing age, chronic obstructive pulmonary disease (COPD) and previous respiratory infections also increase the risk of developing CAP. In older patients, alcoholism, asthma, immunosuppressive therapy, lung diseases, heart disease, institutionalisation and increasing age are related to the risk of contracting pneumonia.

Situations where many people are in close contact (e.g. schools, army barracks, prisons, shelters for the homeless) facilitate the spread of some of the more infectious causes of pneumonia, leading to local epidemics. Certain occupations (e.g. farming) are linked to some of the most common causes of pneumonia.

Preventing people from starting to smoke and stopping those who already smoke is one of the most important means of controlling pneumonia. Vaccination against some organisms (influenza, pneumoccocus) reduces the likelihood of pneumonia in vulnerable groups.

Treatment of pneumonia

Early treatment of pneumonia with antibiotics can cure bacterial pneumonia. Most people will get better at home, but more severely ill people will have to go to hospital.

Reproduced by kind permission of the European Lung Foundation