Pneumonia is a common illness and means infection in the lung. This infection mainly affects the alveoli of the lungs. These are tiny air sacs in the lung. They take oxygen from the air you breathe in. They send this oxygen to the blood stream, which then travels around the body. When there is an infection in the lung, the alveoli fill up with mucus. This prevents the lungs from taking up enough oxygen from the breathed-in air. This leads to shortness of breath. The mucus may be coughed up as phlegm (or sputum). Inflammation caused by the infection can cause a fever and pain on the side of the affected lung.


Pneumonia is caused by a variety of bacteria, viruses and fungi. These are inhaled from the air into the lungs. Normally, the immune system in the nose, upper airways and lungs is able to deal with bacteria and viruses inhaled from the air. However, the immune system can break down. This can be due to old age or co-existing illness. It can also break down if the inhaled organism is too strong for the immune system to deal with. Sometimes, bacteria that normally "live" in the throat and are normally harmless can get into the lungs if the lung's immune system is lowered. Any healthy person can get pneumonia. This can happen if the bacteria or virus is not cleared by the lung's immune system. A common reason for healthy people to get pneumonia is after having a viral infection, such as influenza. This lowers the lungs' defence mechanisms.Certain people are more at risk than others. Elderly people, people with other serious illnesses such as cancer and heart or kidney disease and people whose immune system is not working properly are at increased risk. People with pre-existing lung disease (e.g. chronic bronchitis and emphysema) are very prone to pneumonia. Smokers are more at risk because the cigarette smoke affects the normal immune system in the lungs.

Aspiration pneumonia is one type of pneumonia. It occurs when food or liquids from the mouth, food pipe or stomach accidentally slip into the lungs. In the normal person, food or drinks should not pass into the lungs. This is because a trapdoor in the throat (the epiglottis) is moved as food or drinks pass by the entrance to the airway. Anything that weakens the muscles which move the epiglottis, such as coma, stroke, seizures, alcohol and some drugs, can allow food or liquids from the mouth, food pipe or stomach to spill into the lungs. This causes aspiration pneumonia. Anything that impairs the cough reflex, such as stroke or loss of consciousness, can also lead to aspiration pneumonia. Poor dentition can also lead to aspiration pneumonia if the bacteria from the infected teeth get into the lungs.


The most common cause of pneumonia is a bacteria called streptococcus pneumoniae. This causes 8 out of 10 cases of pneumonia. Other causes include mycoplasma pneumoniae. This is especially seen in young people (teenagers and 20-30 year olds). Staphylococcus pneumoniae is a bacteria that can cause pneumonia after infection with the influenza ('flu) virus. This can be a serious, and sometimes fatal, pneumonia. Legionella pneumoniae causes Legionaire's disease. This is a type of pneumonia caused by breathing in the bacteria from airconditioning systems. Viruses usually cause pneumonia in young children. People who have come into contact with bird droppings, such as poultry workers, are at risk for pneumonia. This is caused by the organism chlamydia psittaci. People whose immune system is not working properly (e.g. people with HIV or leukaemia or after chemotherapy) can develop pneumonia that is caused by very unusual viruses and fungi.

Sometimes, pneumonia can be picked up in hospital. This is from bacteria in the hospital air. The bacteria that cause pneumonia in the hospital are different to those that cause pneumonia outside of the hospital. Hospital bacteria tend to cause a more severe illness. The big problem with this type of pneumonia is that the bacteria in the hospital air have been exposed to many different antibiotics. This means that the bacteria will develop a resistance to the antibiotics normally used to treat pneumonia. Stronger antibiotics are therefore needed. These stronger antibiotics often need to be given through a drip.


Symptoms vary. Pneumonia can be a mild or very severe illness. You may notice shortness of breath, cough, fever, shivering or pain in the chest on the affected side. The pain is especially noticeable with deep breathing and coughing. This chest pain is called pleurisy. It is caused by inflammation of the lining of the lung beside the area of infection. The cough may be dry, or productive of phlegm. The phlegm can be green, brown or bloodstained. Some people may have none of these symptoms. They merely feel "under the weather" or have flu-like symptoms. People with mycoplasma pneumoniae infection are especially prone to flu-like symptoms. These include muscle aches and headache. Elderly people, especially those in hospital, may become confused with pneumonia, without any other typical symptoms. Vomiting and dehydration may occur.


Your doctor will often be able to diagnose pneumonia by listening to your symptoms or examining your chest. No further tests may be needed. However, in many cases, a chest x-ray will be performed. This often shows abnormal shadowing in the lungs due to the infection. Sometimes, the doctor will send samples of your phlegm to the laboratory. This is to see what bacteria are growing. Blood tests may also be needed.


Pneumonia is treated with antibiotics. Your doctor may use one antibiotic or a combination. Generally, if you are not too ill, a 7-10 day course of antibiotic tablets at home will be enough. Actually, some people with mild pneumonia may clear the infection without any medication. People who are sicker, elderly people and very young children may be admitted to hospital. This is for stronger antibiotics and observation. In this case, the antibiotics are usually given through a drip, at least at first. The type of antibiotics and the length of treatment will depend on the how severe the illness is. It also depends on which germs have caused the pneumonia. Oxygen treatment may be needed if your blood oxygen is low.

infection clears. Complications are usually only seen in very elderly people or people with other serious illnesses. However, the outcome can also depend on the bacteria involved.


Pneumonia is more common in smokers. Smoking should therefore be avoided. Many cases of pneumonia occur after an influenza infection. Because of this, certain people such as very elderly people or people with chronic heart, lung or kidney diseases or cancer should be given the influenza vaccination every autumn. These same people should also probably receive vaccination against streptococcus pneumoniae (PneumoVax).