Pneumonia - An Overview

Written by Clement Mbah, MD, PhD, MBChB | Published on October 09, 2021

What is Pneumonia?

Pneumonia is defined as the disease of the lower part of the airways.  It is due to the infection of one or both lungs commonly by bacteria and viruses, or fungi. The disease manifests as fever (which does not subside at any time of the day), difficulty breathing, cough, and chest pain. 

Pneumonia is usually classified as community or hospital-acquired (which is usually found in people with low immunity). It can also be classified based on the part of the airway that is affected or based on the microorganism responsible for the infection.

Pneumonia is a contagious disease, that is - it can be transmitted from one person to another. The commonest means of transmission is usually through breathing in airborne droplets from a sneeze or cough of an infected person.

Anyone can get pneumonia,  however, it is more common among children younger than 2 years and adults older than 65 years, also in persons with immune-compromised.

Epidemiology of Pneumonia

The incidence of pneumonia in most communities was estimated to be 5-11/1000. It is common in infants and the elderly. It also occurs in people with low immunity; people living with HIV who are not compliant with their medications or untreated.

The mortality rate in adults treated at home was estimated to be less than 1%, while hospital death rates are typically between 5-10 per cent but maybe as high as 50 per cent in severe illnesses.[2]

Causes of Pneumonia

Pneumonia can be caused by bacteria, viruses, and fungi.

  • Bacteria: - Streptococcus pneumonia is the commonest, others include Haemophilus influenza, mycoplasma pneumonia, staphylococcus aureus.
  • Viruses: - commoner in children, RSV is the commonest virus, others are COVID-19, influenza virus, etc.
  • Fungi: - Commoner in people with low immunity. Pneumocystis jiroveci is a common causative agent.[2]

The lungs are made up of small sacs which are called alveoli. The alveoli are filled with air when a healthy individual breathes. When the lungs are infected, the alveoli get filled with pus and are unable to receive air.

After the infection persists without treatment, the pus becomes thickened. This makes the affected part of the lung lose the ability to expand to receive air.

Symptoms Of Pneumonia

Symptoms of pneumonia can vary depending on the following;

  • Microorganisms implicated as the cause of the pneumonia
  • The  age of the infected person
  • The health status.

 These symptoms usually develop over several days. They include;

  • Fever
  • Cough (usually painful, dry initially but later associated with the production of sputum containing mucus and pus). Rust-coloured/bloody sputum may be seen in some patients.
  • Breathlessness
  • Chest pain
  • Rigours ( a sudden feeling of cold with shivering accompanied by a rise in body temperature)
  • Generalized body weakness

These symptoms are similar to those of the currently ravaging COVID-19. Covid19 is a type of viral pneumonia caused by a novel coronavirus known as SARS-COV2. So, if you develop any of these symptoms, quickly contact your doctor for proper evaluation of your condition.

Risk Factors of Pneumonia

These are factors that can predispose a person to develop pneumonia. These include;

  • Upper airway infection ( which can descend into the lower airway regions)
  • Cigarette smoking
  • Malnutrition ( This lowers the immune system and predisposes to developing pneumonia).
  • Indoor pollution
  • Alcohol
  • Pre-existing lung disease
  • Corticosteroid therapy (lower the immune system making people susceptible to infection)
  • HIV positive status (people living with HIV who are not drug adherents or who are untreated are predisposed to pneumonia).

Types of Pneumonia

Pneumonia can be classified into different categories based on the causes, means of infection, and so on. Types include;

  • Bacteria pneumonia (refers to pneumonia caused by bacteria infection of the lungs).
  • Viral pneumonia (refers to pneumonia caused by a viral infection of the lungs. An example is COVID19).
  • Fungi pneumonia (causing fungi infection of lungs).
  • Community-acquired pneumonia (refers to pneumonia that is acquired outside of a medical setting or hospital).
  • Hospital-acquired pneumonia (ref. pneumonia acquired in the hospital, is usually more serious than other types because the bacteria involved are more resistant to antibiotics).
  • Aspiration pneumonia ( happens when bacteria get into the lungs from aspiration of food, drinks, or saliva)

Diagnosis of Pneumonia

To make a diagnosis of pneumonia, your doctor will ask questions about the symptoms, examine you, listen to your lungs, and request some investigations. These investigations include;

  • Chest X-ray (usually provides confirmation of the diagnosis, gives a visual assessment of the spread of the infection in the lungs).
  • Sputum microscopy, culture, and sensitivity (to grow the causative organism from sputum)
  • Blood culture ( to grow the causative organism of pneumonia)
  • Pulse Oximetry (measures the level of oxygen in the blood).
  • Bronchoscopy ( to visualize the airway for blockages or other problems)

Treatment and Management of Pneumonia

The treatment will depend on the type of pneumonia and how severe it is. For bacteria pneumonia, the mainstay of treatment is oral antibiotics, while for viral pneumonia the treatment is a majorly supportive therapy although antiviral drugs can be used. Antifungal medications are the mainstay of treatment for fungi pneumonia.

Supportive therapy includes;

  • Oxygen therapy
  • Analgesics (Paracetamol, aspirin)
  • Intravenous fluids
  • Expectorants ( to help reduce the cough)

The doctor would also advise sufficient rest, drinking enough fluids, and a good diet.

Pneumonia Complications

Untreated pneumonia can lead to more harmful conditions. These include;

  • Bacteremia and Septic shock: Bacteremia is a condition that occurs when the organism causing pneumonia enters the bloodstream. This can proceed to Septic shock, which manifests as very low blood pressure.
  • Lung abscesses: Pneumonia can cause pockets of pus to build up in the lungs, and this is known as an abscess.
  • Pleural effusion and Empyema: The pleura are two layers covering the lungs. They help the lungs to move smoothly during breathing. In pneumonia, the layers become swollen leading to sharp chest pain felt during breathing. If not treated, fluid accumulates within the layers. When the fluid gets infected by the causative organism, empyema occurs.

In this condition, the infected person will not want to breathe deeply because it hurts. They feel pain in the back and shoulders too.

  • Pneumothorax (Accumulation of air around the lungs)
  • Acute respiratory distress syndrome
  • Meningoencephalitis ( when the causative organism enters the bloodstream and travels to the brain, it infects the brain coverings and the brain matter).

Prevention of Pneumonia 

The risk of getting pneumonia can be reduced by addressing the predisposing factors such as;

  • Stopping smoking
  • Taking a balanced diet (malnutrition is a major risk factor for developing pneumonia).
  • Vaccination against COVID-19, Influenza, pneumococcal, measles vaccinations

Healthcabal Note

Most people who develop pneumonia respond promptly to medications. Fever may persist several days and the chest x-ray often takes several weeks or months to resolve, especially in old age. Delayed recovery suggests a complication has occurred or the initial diagnosis was incorrect.


Pneumonia is a very common disease around us and it can affect anyone.  The present COVID-19 pandemic is a viral pneumonia illness, so knowledge of the condition is quite important for everyone.


References :

  1. Davidson principles and practice of medicine 21st edition- Pathogenesis of Pneumonia.
  2. WHO - Pneumonia fact sheet [2]
  3. Oxford Handbook of Clinical medicine - Causative organisms for Pneumonia

Further reading: