Pneumonia is an infection of the lungs with a range of possible causes. It can be a serious and life-threatening disease. It normally starts with a bacterial, viral, or fungal infection.

The lungs become inflamed, and the tiny air sacs, or alveoli, inside the lungs fill up with fluid.

Pneumonia can occur in young and healthy people, but it is most dangerous for older adults, infants, people with other diseases, and those with impaired immune systems.

Symptoms

The first symptoms of pneumonia usually resemble those of a cold or flu. The person then develops a high fever, chills, and cough with sputum.

Common symptoms include:

• cough
• rusty or green phlegm, or sputum, coughed up from lungs
• fever
• fast breathing and shortness of breath
• shaking chills
• chest pain that usually worsens when taking a deep breath, known as pleuritic pain
• fast heartbeat
• fatigue and weakness
• nausea and vomiting
• diarrhea
• sweating
• headache
• muscle pain
• confusion or delirium, especially in older adults
• dusky or purplish skin color, or cyanosis, from poorly oxygenated blood

Symptoms can vary depending on other underlying conditions and the type of pneumonia.