Pneumonia

Pneumonia is an infection of the lungs that can be caused by a virus or by bacteria. The lungs contain thousands of small airways, called bronchi, which end in tiny air sacs called alveoli. Each air sac is surrounded by a fine mesh of capillaries, where oxygen is added to the blood and carbon dioxide is removed.

When a person has pneumonia, the air sacs in one or both lungs fill with pus and fluid (exudate), which interferes with this exchange of gases. This is sometimes described as “consolidation” of the lung.

Anyone of any age can develop pneumonia, but it is most common in children aged four years and under and in older adults.

Symptoms#

Pneumonia can come on suddenly or develop gradually. The symptoms depend on the age of the person, the cause and severity of the infection, and any existing problems with immunity. With appropriate treatment, most people can expect to recover in around seven to 10 days.

Symptoms may include:

• rapid breathing
• breathing difficulties
• fever
• a general feeling of being unwell (malaise)
• loss of appetite
• abdominal pain
• headache
• chest pain
• cough
• a blue coloration of the skin around the mouth (cyanosis), caused by a lack of oxygen

Causes#

Pneumonia is often triggered by a cold or a bout of flu, which allows germs to reach the air sacs. In about half of all cases, no specific cause is ever identified. The micro-organisms that can cause pneumonia include the following.

Bacteria#

Bacterial pneumonia can cause symptoms such as rust- or green-colored phlegm. Anyone can be affected, but more susceptible groups include babies, older adults, people who misuse alcohol, and people recovering from surgery or coping with other illnesses such as lung disease.

Viruses#

Viral pneumonia tends to cause symptoms similar to a severe bout of flu. It is thought that around 50 per cent of pneumonia cases are caused by viral infections.

Mycoplasma#

Mycoplasma is a special kind of bacteria. Pneumonia caused by mycoplasma is generally mild, but recovery takes longer. Symptoms can include white phlegm, nausea, and vomiting.

When to see a doctor#

If your child seems to be recovering well from a cold or flu but then relapses, they may have a chest infection. See your doctor straight away, because pneumonia can be life threatening to babies and young children.

Diagnosis#

Pneumonia is diagnosed using a combination of tests, such as a general examination and chest x-rays.

Treatment#

In many cases the person’s own immune system can clear the infection, but antibiotics are sometimes used to assist recovery. Treatment depends on the age of the person and the type of infection, and may include:

• hospital admission, particularly for babies and young children
• plenty of fluids, taken by mouth or intravenously
• antibiotics to treat the infection, if bacteria are the cause
• medications to relieve pain and reduce fever
• rest

Immunization#

One of the most common types of bacterial pneumonia is pneumococcal pneumonia, caused by infection with Streptococcus pneumoniae. There are vaccines against this bacterium that reduce the risk of infection.

Vaccination is generally recommended for people at higher risk, who can include:

• young children
• older people, especially those over the age of 65 years
• people with chronic illnesses such as diabetes, asthma, or respiratory disorders
• people with reduced immunity
• people who have had an organ transplant
• people who have a damaged spleen or have had their spleen surgically removed

Key points#

• Pneumonia is a lung infection caused by a virus or bacteria.
• With appropriate treatment, most people recover in around seven to 10 days.
• Symptoms can include rapid breathing, fever, cough, chest pain, and, when oxygen is low, a blue coloration around the mouth (cyanosis).
• In about half of all cases, no specific cause is ever found.
• Vaccines are available against pneumococcal pneumonia and are recommended for people at higher risk.

Where to get help and trusted information#

For evidence-based global health guidance, see Source: World Health Organization (WHO).