Pneumonia is an infection caused by microorganisms like bacteria, viruses or fungi. It occurs in the lower respiratory tract. The symptoms of pneumonia can range from being moderate to life-threatening.

Although pneumonia is known to occur in individuals of any age group, severe pneumonia is more common in children who are very young and adults over 65 years. As reported by the WHO, pneumonia is the leading cause of death in children below 5 years of age. Pregnant women, people with underlying serious illness and those with a weak immune system are at a higher risk for severe pneumonia. Research also proves that individuals on mechanical ventilation or chemotherapy and those who have received an organ donation are prone. People who have AIDS are also extremely susceptible to pneumonia.

Microorganisms are constantly present in the environment around an individual. In a healthy individual, the body defense mechanisms are capable of protecting the lungs and respiratory tract from severe infections. The body defenses against respiratory infections include the coverings of the respiratory tract, the mucous and the hair-like structures that trap and remove many disease-causing germs from the airways. If these disease-causing germs or pathogens pass through these initial defense systems, they are then destroyed by immune system cells that identify them as foreign bodies and prevent them from creating further damage. Pneumonia occurs when these defense systems are damaged, weakened or when the pathogens that invade overpower the defense systems.

Some types of pneumonia are more common in some seasons. Seasonal changes and climatic conditions make some microorganisms more prevalent in nature than usual. Therefore, pneumonia becomes more common in some seasons.


Pneumonia is caused most commonly by bacteria and viruses and less commonly by fungi or parasites. The causes differ according to the age of the person, time of the year, the health status of the person and also the place from where the infection has occurred.

Most common causative agents  of pneumonia are as follows:

Bacterial causes

Pneumonia can be caused by various types of bacteria. Bacterial pneumonia is more common in adults.

Elderly, who suffer viral respiratory infection, can have additional infection due to bacteria that leads to pneumonia. These are called secondary pneumonia.

The most common causes of bacterial pneumonia is Streptococcus pneumoniae also called pneumococci. Pneumonia caused by Streptococcus pneumoniae is called pneumococcal pneumonia.

These bacteria are easily spread through direct contact or by coughing and sneezing.

The less common causes of bacterial pneumonia are:

  • Haemophilus influenza type B (Hib) causes pneumonia in children less than 5 years of age. It can also cause other infections like meningitis, and ear infections. However, due to Hib vaccinations, these infections are now less common.
  • Moraxella catarrhalis is seen as a part of the harmless bacteria of our mouth and throat. But it can cause pneumonia in children and adults with other lung diseases like Asthma and COPD. Usually, It causes ear infections and sinusitis in children.
  • Staphylococcus aureus pneumonia is more common in hospitalized patients or following the viral flu. These infections can become severe and difficult to treat as they are resistant to multiple antibiotics.
  • Klebsiella pneumonia can cause pneumonia in hospitalized patients on a ventilator. It can also cause pneumonia in alcoholics.
  • Streptococcus agalactiae (Group B strep) is a bacteria seen in the female vagina. They can be passed from a pregnant woman to her baby during childbirth and cause severe infections in the newborns. They can also cause infections in the elderly who have diabetes or neurological disease.
  • Pseudomonas aeruginosa can cause pneumonia in individuals with decreased lung function like cystic fibrosis, individuals with low immunity and hospitalized individuals.

Based on the geographical location of the individual, the type of bacteria causing the infection could vary. In such cases, travelers and tourists who migrate from certain countries may be exposed to bacteria types that are less common in their own geographical location. In some cases, a person may be exposed and become vulnerable to a rare type of bacterial pneumonia due to his weakened immune system or an underlying health condition.

Viral causes

About one-third of all pneumonia cases occur due to viruses that infect the respiratory system. Viral causes are usually the most common cause of pneumonia in children. Viral causes are also very common in adults over 60-65 years of age.

Depending on the type of virus, age and the immunity of the individual affected, viral pneumonia can range from mild to severe infections.

The most common viruses that cause pneumonia are

  • Influenza Virus is the most common cause of viral pneumonia.
  • Parainfluenza Virus can also cause respiratory infections in infants, which further develop into pneumonia.
  • Respiratory Syncytial Virus is the most common cause of pneumonia in children below 1 year of age.
  • Other viruses which cause pneumonia include adenoviruses, cytomegalovirus, measles, and rhinoviruses.

Fungal causes

Pneumonia due to fungi is less common. Fungal pneumonia is more commonly seen in people who have a weak immune system. These include recipients of organ transplants, individuals with AIDS, diabetes and those on chemotherapy treatment for cancer. The fungi that cause infection in these people are usually referred to as “opportunistic.”

Some examples of opportunistic fungi are

  • Aspergillus species common cause for aspergillosis and fungal masses in the sinus and lungs. They can cause lung infections in individuals with asthma or COPD.
  • Rhizopus and Mucor they commonly cause sinus infections in diabetes
  • Pneumocystis jirovecii is very common in individuals with AIDS
  • Certain fungi, called endemic fungi, can also cause pneumonia and severe infections in healthy adults. These fungi are less common but are highly prevalent in areas with caves and rivers. The examples include
  • Histoplasma
  • Coccidiodes
  • Sporothrix

Parasitic pneumonia

Pneumonia due to parasites is the least common. They are more common in individuals with severe defects in their immunity. Examples include

  • Toxoplasma
  • Hookworms, pinworms and flukes
  • Filariasis


Symptoms of pneumonia vary based on the age of the affected individual, his or her health condition and the type of microorganism that is causing the infection.

In newborn babies, the common symptoms are wheezing, grunting, breathing rapidly, irritability and lethargic behavior. Mild symptoms of pneumonia resemble that of a regular cold or flu but they tend to last longer.

Common symptoms of pneumonia include:

  • Fever, chills, and sweating
  • Cough, with or without phlegm
  • Chest pain
  • Difficulty in breathing
  • Nausea and vomiting
  • Bronchitis treatment
  • Muscle pains
  • Headache
  • Fatigue
  • Confusion

Pneumonia can progress and become life-threatening in some individuals. And hence, with medical assistance must be initiated as early as possible.

Risk factors

Pneumonia can occur in anyone but the following individuals are at highest risk.

  • Children below 2 years of age
  • Adults over 65 years of age
  • Hospitalized individuals: Hospitalisation increases the risk of exposure to micro-organisms, especially in those who require a ventilator.
  • Presence of chronic diseases: Having chronic diseases like asthma, chronic obstructive pulmonary disease (COPD), or heart diseases can make an individual more vulnerable to pneumonia.
  • Smoking: Smoking usually results in the damage of the body’s natural defense systems against bacteria and viruses, making individuals more prone to infections like pneumonia.
  • Weak immune system: People with severe underlying health conditions like HIV/AIDS, those who have had an organ transplant, those on chemotherapy regimen or long-term usage of steroids are at higher risk for pneumonia.


Diagnostic tests for pneumonia detect the presence of pneumonia, the microorganism causing the infection and the extent of damage tothe lungs. Diagnosis is also essential to limit the spread of infection, to understand its severity and also as a guide to the treatment that is to be given.

Common infectious organisms are usually difficult to be identified, and therefore the medical history or the patient, identification of common agents in the community and the patient’s clinical presentation are taken into consideration. In cases where symptoms do not resolve after a primary treatment, additional testing may be performed to diagnose and identify less common causes of pneumonia.

Based on the symptoms displayed by the person and his health status, various laboratory tests may be performed for accurate diagnosis. Commonly prescribed diagnostic tests that can be done in a laboratory include:

  • Complete Blood Count (CBC): The presence of infection may be detected by the number of white blood cells or WBC present in the blood.
  • Basic Metabolic Panel (BMP): Tests for sodium, potassium and other elements in order to determine the severity of the infection.
  • Arterial Blood Gases or ABG: This test measures pH and the amount of oxygen and carbon dioxide in the blood. This is an indication of lung function.

In order to diagnose the presence of bacteria, the common tests prescribed are:

Sputum Culture/Gram Stain: Primary test to identify the bacterial cause of pneumonia. Culture can also identify the antibiotics to which the bacterial agent is susceptible.

AFB Smear and Culture: Tuberculosis can also present like pneumonia. This test is required to identify tuberculosis bacteria in the lungs.

Blood Culture: This test is done when it is suspected that infection has spread from lungs to blood or from blood to the lungs.

Pleural Fluid Analysis: Sometimes fluid collects around the lungs between its coverings. This fluid is tested for identifying the cause of pneumonia.

Special Test:  Special tests can identify specific causes of pneumonia. These include those which cannot be cultured Examples are

  • Mycoplasma
  • Legionella
  • Influenza Tests
  • RSV Testing
  • Fungal Tests

Chest X-ray: Chest X-ray detects and evaluates the severity of a lung infection. When a patient has pneumonia, the affected lung may show up on the chest X-ray as patches.

Computed Tomography Scan (CT Scan)  is used to detect and evaluate the structure of the lung and the changes due to pneumonia.


Treatment for pneumonia varies depending on the type and severity of the infection. Various medications for pneumonia include:

  • Antibiotics: These medicines work on the bacteria. Antibiotics are prescribed by the doctor based on the type of bacteria causing pneumonia. If the symptoms fail to ease, replacement of antibiotics is done.
  • Cough Medicine: Severe coughing can be troublesome for patients. Cough medication reduces cough and helps the patient rest. A cough is sometimes required to remove fluid from the lungs. in such cases, the low dose of cough medicine might be reduced.
  • Antipyeretics: When a person is experiencing discomfort due to fever and pain during the infection, medications to reduce fever and pain, like paracetamol, are prescribed.
  • Admission into the hospital may be required in severe infections, individual over 65 years of age, or if they have variations in blood pressure, damage to kidney function, rapid breathing, confusion, low/high heart rate and breathing difficulties.
  • Children may require hospitalization if they are younger than 2 months of age or if they are lethargic, having a high fever and experiencing breathing difficulties. If the child appears dehydrated, it is also a sign to get them hospitalized.
  • For those who have been infected with pneumonia, getting plenty of rest, staying hydrated and taking medicines as prescribed can help decrease the risk of complications and aid in speedy recovery.


Some practices can help prevent pneumonia and serious illness.

  • Vaccination: The most common types of pneumonia can be prevented by vaccination. The vaccine available include
  • Pneumococcal Vaccine: This vaccine protects the individual from serious infections of Streptococcus pneumonia. Two types of pneumococcal vaccine are available. These are the pneumococcal polysaccharide vaccine(PPSV23) and pneumococcal conjugate vaccine (PCV 13).
  • Hemophilus influenza vaccine or Hib vaccine prevents pneumonia due to Hemophilus influenza.
  • Other relevant vaccines include influenza vaccine, chicken pox vaccine, MMR

Some other preventive measures include:

  • Thorough and frequent washing of hands
  •  Covering of the nose while sneezing
  • Cleaning and disinfecting surfaces like door knobs, handles, keyboards, remotes, mobile phones and other items that are frequently touched by hands.
  • Avoiding touching face, eyes, nose and mouth without washing hands
  • Avoiding close contact with those who have cold and cough respiratory infections
  • Stop smoking


How can I prevent my baby from pneumonia?

Vaccinations are the safest preventive measures against pneumonia and other fatal infections in infants.

Does pneumonia result in death?

Untreated pneumonia can be fatal for babies under 2 months of age and also for adults with underlying health conditions.

How long does it take to recover from pneumonia?

Pneumonia can be considered as a mild illness in people who are healthy and can, therefore, be cleared in 2 to 3 weeks of time. In those with other health issues and in older adults, it can take upto 2 months or more.

What are the early signs of pneumonia?

A cough and fever is an early sign of pneumonia. Usually, the cough is associated with phlegm or sputum that comes from the lungs during the infection.

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