Pneumonia is an infection or inflammation of the air sacs (alveoli) in the lungs. Pneumonia is a serious condition in which fluid and/or pus get(s) into the alveoli, blocking them and preventing oxygen from reaching the blood. The lack of oxygen will make you breathless and starve your body’s organs of the oxygen they need to function properly. The extensive inflammation usually causes other symptoms as well, such as fever, chills, tiredness and chest pain.
Pneumonia is a common disease, particularly in winter and spring due to the increased circulation of bacterial and viral respiratory infections that often occurs at those times of year. However, it can be fatal, particularly for people who are sick, very old or very young. Doctors estimate that up to 15 per cent of people who are hospitalised with pneumonia may die from it.
Pneumonia is not a single illness — doctors estimate that there are at least 30 causes of pneumonia, some of which are more likely to be life-threatening than others. However, most pneumonias are caused by:
In most cases, pneumonia starts after the infectious agent is inhaled into the lungs. However, sometimes the infection gets to the lungs by other means, carried there by the bloodstream or by being transported to the lungs from a nearby infection in the body. In many people who have pneumonia, the exact cause can’t be identified despite extensive testing.
Sometimes pneumonia can occur after a person remains immobile after surgery or an injury. Shallow breathing and not being able to cough properly may lead to mucus being retained in the lungs which makes a person more susceptible to bacterial infection. This is one reason that bedridden people are at a high risk of developing pneumonia.
While any person can catch pneumonia, some people may be more at risk than others. These include heavy drinkers or smokers and people who have chronic conditions such as heart failure, diabetes or chronic obstructive pulmonary disease (COPD).
People with compromised immune systems, including those affected by AIDS, may contract a type of pneumonia known as Pneumocystis carinii pneumonia, which is caused by a type of microorganism. Often the appearance of this pneumonia is the first sign of AIDS developing in people infected with HIV.
Last Reviewed: 05 August 2009