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.

Signs and Symptoms

  • 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


Bacteria and viruses are the main causes of this disease. This disease-causing germs can settle in the alveoli and multiply after a person breathes them in.

The bacteria and viruses that cause pneumonia are usually inhaled. They can be passed on through coughing and sneezing or spread onto shared objects through touch.

The body sends white blood cells to attack the infection. This is why the air sacs become inflamed. The bacteria and viruses fill the lung sacs with fluid and pus, causing pneumonia.

Risk Factors

Those most at risk include people who:

  • Children under 5 years or over 65 years
  • Smoke tobacco, consume large amounts of alcohol, or both
  • Have underlying conditions such as cystic fibrosis, chronic obstructive pulmonary disorder (COPD), asthma, or conditions that affect the kidneys, heart, or liver
  • Have a weakened or impaired immune system, due, for example, to AIDS, HIV, or cancer
  • Take medicines for gastro esophageal reflux disease (GERD)
  • Have recently recovered from a cold or influenza infection
  • Experience malnutrition
  • Have been recently hospitalized in an intensive care unit
  • Have been exposed to certain chemicals or pollutants


Treatment depends on the type and severity of the pneumonia.