What is pneumonia?

Pneumonia is a lung infection, usually caused by bacteria or viruses. If you have pneumonia, you may experience a bad cough, a fever and difficulty breathing. Pneumonia is most likely to develop after having a cold or flu.

Each lung is filled with thousands of small airways that branch into tiny air sacs, which allow oxygen from the air we breathe to enter the blood. If you have pneumonia, these air sacs in the lung fill with fluid and mucus, which interferes with the breathing process.

Pneumonia can affect people of any age, but is more common in young children, the elderly and people with weak immune systems. Treatment for pneumonia depends on the severity and the specific cause, but includes a combination of medication and self-care treatments, including getting plenty of rest and drinking lots of fluids.   

Immune systems

The organs and cells involved in protecting the body against infection.

Mucus

A thick, viscous liquid that is secreted for lubrication and to form a protective lining over certain tissues.

Causes

Pneumonia is usually caused by an infection with bacteria or viruses that have been inhaled into the lungs. Your body's immune system then sends white blood cells to attack the germs that are causing the infection. This causes the air sacs in the lung, called alveoli, to become filled with fluid and mucus, which can cause difficulty breathing.

Lungs showing healthy alveoli and fluid-filled alveoli in pneumonia.Pneumonia causes alveoli in the lung to fill with fluid and mucus. 

Immune system

The organs and cells involved in protecting the body against infection.

Mucus

A thick, viscous liquid that is secreted for lubrication and to form a protective lining over certain tissues.

White blood cells

Cells of the immune system that participate in immune and inflammatory reactions.

Risk factors

Anyone can get pneumonia, but young children and people over the age of 65 have a higher risk of developing the condition. Some other factors that can increase your risk of getting pneumonia include:

Bronchiectasis

A condition in which the airways are damaged and become dilated, losing their ability to clear mucous.

Corticosteroids

A medication that resembles the cortisol hormone produced in the brain. It is used as an anti-inflammatory medication.

Immune system

The organs and cells involved in protecting the body against infection.

Types

Bacterial pneumonia

Bacterial pneumonia is caused by bacteria. The most common type of bacteria that cause this form of pneumonia is Streptococcus pneumoniae. Other bacteria that cause pneumonia include Klebsiella pneumoniae and Haemophilus influenzae, which are more common in people with weak immune systems.

Viral pneumonia

Viral pneumonia is caused by infection with a virus. Some of the common types of viruses that cause this type of pneumonia include the influenza virus (which also causes the flu), adenoviruses and rhinoviruses (which cause colds).

Fungal pneumonia

Fungal pneumonia is a rare type of pneumonia caused by a fungal infection. It is more common in people with weak immune systems, which includes people who are taking medications to suppress their immune system and people who have HIV/AIDS. Some of the common causes of fungal infections that can lead to this type of pneumonia include Histoplasmosis, Coccidiomycosis, Blastomycosis, Aspergillosis and Cryptococcosis.

Parasitic pneumonia

Although uncommon, some types of parasites can also cause pneumonia. They can enter the body through direct contact with the skin, through the mouth, or through an insect bite. Some of the parasites that can cause pneumonia include Toxoplasma gondii, Strongyloides stercoralis, Ascarislumbricoide and Plasmodium malariae.

Adenoviruses

A family of viruses that cause primarily respiratory diseases, conjunctivitis and gastroenteritis.

Immune systems

The organs and cells involved in protecting the body against infection.

Rhinoviruses

A common group of viruses, including those that cause the common cold.

Signs and symptoms

If you have pneumonia you may experience some of these symptoms:

  • A cough that produces mucus;
  • Fever;
  • Shaking and chills;
  • Shortness of breath or rapid breathing;
  • Chest pain;
  • Fast heartbeat;
  • Tiredness or feeling very weak;
  • Sweating;
  • Headache, and;
  • Muscle pain.

Mucus

A thick, viscous liquid that is secreted for lubrication and to form a protective lining over certain tissues.

Methods for diagnosis

Working out if you have pneumonia can be hard, because some symptoms are very similar to a common cold or flu. If your doctor suspects that you have pneumonia, a diagnosis will usually be made based on the results from a physical exam, an X-ray of your chest and laboratory test results.

Physical examination

During a physical examination, your doctor may use a stethoscope to listen to your lungs for crackles and other unusual sounds when you breathe. Gently tapping on the chest, by your doctor, may elicit dullness that can also suggest pneumonia.

X-ray

Your doctor may take an X-ray of your chest to confirm if you have pneumonia and determine which part of your lungs are affected.

Laboratory tests

A blood test or a sample of sputum that is coughed up may be used to help work out whether the cause of your pneumonia is bacterial, viral or fungal.

Sputum

Mucus and possibly pus, bacteria and blood that is coughed up from the airways, typically as a result of an infection.

X-ray

A scan that uses ionising radiation beams to create an image of the body’s internal structures.

Types of treatment

Pneumonia is usually treated with a combination of medication and self care. Your specific treatment will depend on how bad your condition is and what is causing it. If you have very severe symptoms or have a weak immune system, you may need to go to hospital.

Self care

For mild cases of pneumonia, self-care treatments may help recovery. These include getting plenty of rest, drinking lots of fluids and avoiding cigarette smoke.

Medications

Mild bacterial pneumonia can be treated with oral antibiotics including amoxicillin and clavulanic acid, doxycycline or roxithromycin. Very severe bacterial pneumonia may need to be treated in hospital with intravenous antibiotics, such as benzylpenicillin.

Mild viral pneumonia is usually treated with self care. Over-the-counter pain-relief medications such as paracetamol, or anti-inflammatory medications such as ibuprofen, might help in reducing some of the symptoms of pneumonia.

Fungal pneumonia is usually treated with antifungal medications.

Immune system

The organs and cells involved in protecting the body against infection.

Prognosis

If left untreated, pneumonia can be life-threatening, but most cases will get better with a combination of proper medical treatment, rest, plenty of fluids and a healthy diet to boost your immune system. You are more likely to recover quickly if your condition is diagnosed and treated early. Most cases of pneumonia will start to improve within a week, but it will often take a few weeks for all symptoms to disappear.

The risk of developing complications from pneumonia is higher in people over the age of 65 and in young children. People who have long-term diseases such as chronic obstructive pulmonary disease (COPD) and HIV/AIDS have a higher chance of developing complications of pneumonia.

Immune system

The organs and cells involved in protecting the body against infection.

Prevention

Avoiding people with a cold or flu and washing your hands before eating, handling food, or touching your mouth or nose can reduce the spread of the bacteria and viruses that commonly cause pneumonia. Other ways to reduce the risk of pneumonia include:

Vaccination

There are two vaccines available that may protect you from the most common bacteria that cause pneumonia. These are the pneumococcal conjugate vaccine, which is usually given to children as part of the childhood immunisation program, and the pneumococcal polysaccharide vaccine, which is generally given to people who have an increased risk of developing pneumonia. These vaccinations may not always prevent people from developing pneumonia, but they may stop the condition from becoming very serious.

A yearly vaccination can help prevent pneumonia. 

Avoiding smoking

Smoking causes damage to the lungs and can make you more likely to develop lung infections. Avoiding and quitting smoking can reduce your chance of getting pneumonia.

Vaccinations

The practice of administering a vaccine, a solution containing a microorganism (that causes a specific disease) in a dead or weakened state, or parts of it, for the purpose of inducing immunity in a person to that microorganism.