Pneumonia is an infection or inflammation of the air sacs (alveoli) in the lungs. Fluid and/or pus get(s) into the alveoli, blocking them and preventing oxygen from reaching the blood.
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. Pneumonia can be a serious illness, particularly for babies and young children, people older than 65 years of age, and people with pre-existing health problems.
What causes pneumonia?
There are many different causes of pneumonia, some of which are more likely to be life-threatening than others. Common causes include:
- mycoplasma (microscopic organisms like bacteria);
- accidentally breathing food, drink or vomit into the lungs (usually in people who are unconscious or have a problem with their gag reflex); or
- inhaling liquid, chemicals or dust into the lungs.
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.
Who is at risk?
Some people may be more at risk of pneumonia than others. These include:
- infants and very young children;
- people older than 65 years;
- heavy drinkers;
- people who have chronic conditions such as heart failure, diabetes or chronic obstructive pulmonary disease (COPD); and
- people with weakened immune systems.
Symptoms of pneumonia depend on the severity of the disease (which is related to the cause of pneumonia and your age and general health).
Common symptoms of pneumonia include:
- cough (dry or productive);
- difficulty breathing or breathlessness;
- chest pain that is worse when coughing or breathing deeply;
- fever and/or chills; and
Some people may experience loss of appetite, nausea, vomiting or diarrhoea. Mental confusion is another symptom of pneumonia (usually in older people).
In bacterial pneumonia, symptoms can appear suddenly and be very severe or may appear more gradually.
Symptoms can include:
- a rapid increase in breathing and pulse rate;
- fever and chills;
- productive cough with green or yellow mucus, or mucus which is red or brown from blood;
- chest pain;
- mental confusion; and
- slightly blue lips and nail beds due to lack of oxygen.
Many cases of viral pneumonia are not serious and only last a short time.
The influenza (flu) virus (the most common cause of viral pneumonia in adults) can cause serious pneumonia, especially in older people or people with impaired immunity.
Symptoms of viral pneumonia can be similar to symptoms of flu, and include:
- dry cough;
- shortness of breath;
- tiredness; and
- muscle pains
In some cases, viral pneumonia may be complicated by a bacterial infection.
Mycoplasma pneumonia is a type of atypical pneumonia, and most often affects people younger than 40 years of age. It can occur as an epidemic in confined groups such as families, students and military personnel. It is usually mild, but can be severe. Sometimes a cough and weakness can go on for a few weeks if it is not treated.
Common symptoms include:
- chills and fever;
- a sore throat;
- a dry cough, which may become productive;
- fatigue, which can last for several weeks after the disease has subsided;
- nausea and vomiting;
- joint pain and muscle aches; and
- in some people, a skin rash.
2. Respiratory tract infections (revised October 2014). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2015 Jul. http://online.tg.org.au/complete/ (accessed Nov 2015).
3. National Heart, Lung and Blood Institute. Pneumonia (updated 1 Mar 2011). http://www.nhlbi.nih.gov/health/health-topics/topics/pnu (accessed Nov 2015).