A Guide to the Pathophysiology of Bacterial and Viral Pneumonia: How Pneumonia Affects the Function of Your Respiratory System

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What is pneumonia? What is the pathophysiology of pneumonia? What are the symptoms of this disease? These are common questions affected individuals and their loved ones often asks about this disease. Pneumonia is considered a killer disease of the lungs. Children, the elderly and individuals with compromised immune system are often the ones who are most prone to getting this infection.


Several types of organisms can cause pneumonia. These include viruses, fungi and bacteria. Inhalation of chemicals as well as injury to the lung tissue may also contr ibute to its development. The most common cause of the disease is the flu virus. Viral pneumonia is frequently less serious compared to other types of pneumonia caused by bacteria and fungi, although in some cases it can also become severe.

Bacterial pneumonia generally develops after a person recovers from cold and flu. This type of pneumonia is more common, however, among those who have just recovered from surgery, have a poor immune system or suffer from other respiratory ailments. The most common bacteria involved are Streptococcus pneumonia, Staphylococcus aureus and Haemophilus influenza.

Pneumonia may also be caused by an organism called Mycoplasma pneumonia. This organism is often the infecting agent in a mild form of pneumonia that affects many young adults. This condition is often called walking pneumonia, as affected individuals may not be aware of its presence and may continue to pursue their usual activities.

Diagnosis is frequently based on the symptoms of the patients, their medical history and findings during physical examinations. A chest X-ray is also often done to visualize the lungs. The treatment of the disease usually depends on its cause.

Pathophysiology of Pneumonia

When the immune system is healthy, it can generally ward off the entrance of entrance of organisms or control them from multiplying and causing disease. Pneumonia may develop even in healthy individuals, however, when the infecting organisms are very strong. Those with weaker immune systems are often the ones who catch pneumonia faster, usually after a flu infection.

As the infecting organism enters the lungs, the lung tissues usually become swollen and inflamed, particularly the air sacs or alveoli. This is often due to the migration of white blood cells in the area to fight off the infection. The alveoli then becomes filled with pus and fluid resulting in the manifestations of fever, cough, breathing problems and chills. The function of the lungs become affected, and oxygen exchange may be reduced and becomes inadequate for the need of the body. This is why pneumonia needs to be treated promptly as severe complications can happen.


Pneumonia can have several serious complications which can even lead to death if not treated promptly. These include respiratory failure and sepsis. Respiratory failure occurs when the lungs lost most of its functions, and may need the use of ventilator as a means of treatment. Sepsis is often a result of the spread of bacteria in the circulation which can lead to shock.


emedicine: Pediatrics, Pneumonia; https://emedicine.medscape.com/article/803364-overview

American Lung Association: Understanding Pneumonia, https://www.lungusa.org/lung-disease/pneumonia/understanding-pneumonia.html