Pneumonia

An infection that inflames the air sacs in one or both lungs, which can fill with fluid. It can be mild or life-threatening.

InfectionLungsLast updated: 21 October 2026

Quick Summary

Primary Symptoms

Cough with phlegm, fever, chills, fast or difficult breathing, chest pain when breathing and tiredness.

Common Treatments

Antibiotics for bacterial pneumonia, rest and fluids. Severe cases need hospital care with oxygen.

Risk Factors

Young children, older adults, smoking, lung disease, weak immune system, and recent flu or COVID-19.

OverviewSymptomsCausesTreatmentFAQ

Overview

Pneumonia is usually caused by bacteria or viruses. The air sacs in the lungs fill with fluid or pus, making it harder for oxygen to reach the blood.

It's a leading cause of death in young children and older adults worldwide. Vaccines against pneumococcus, Hib, flu and COVID-19 help prevent it.

Symptoms

Cough

Often with yellow, green or blood-stained phlegm.

Fever and chills

With sweating and shivering.

Breathlessness

Fast or difficult breathing, even at rest.

Chest pain

Sharp pain that's worse when breathing in or coughing.

Causes & Risk Factors

Biological Causes

Infection of the lungs, most often by bacteria such as Streptococcus pneumoniae, or by viruses such as flu, RSV and SARS-CoV-2.

Key Risk Factors

  • Age Children under 5 and adults over 65.
  • Smoking and lung disease Smoking, COPD and asthma damage the lungs' defences.
  • Weak immune system HIV, diabetes, cancer treatment and malnutrition.

Management & Treatment

01. Diagnosis

A doctor's examination and often a chest X-ray and blood tests.

02. Antibiotics

For bacterial pneumonia. Finish the course even if you feel better.

03. Hospital care

Oxygen, fluids and injectable antibiotics for severe pneumonia.

Frequently Asked Questions

Is pneumonia contagious?
The germs that cause it can spread through coughs and sneezes.
How long does recovery take?
Most people feel better in one to three weeks, but tiredness can last longer.
When is it an emergency?
Difficulty breathing, bluish lips, confusion or chest pain need urgent help.

Sources and further reading

Last updated 21 October 2026. For more detail, see these trusted health organisations.