Pneumonia: Causes, Symptoms, and Treatment


Pneumonia is a serious lung infection that affects people across age groups. Being well-informed can help people seek timely care when required and also take preventive measures. Therefore, we have provided a comprehensive guide to pneumonia by exploring its causes, risk factors, types, symptoms, diagnosis, and treatment options. 

What is Pneumonia?

Pneumonia is swelling of the lungs ‘air passageways.

  • As the air sacs become filled with serum and pus, circulation in the blood is obstructed.
  • Symptoms include chest pain, fever, cough and difficulty of breathing.
  • The risk factors vary depending on the severity of the pneumonia.

Symptoms of Pneumonia

Pneumonia symptoms can vary as per the causes and severity of infection. However, typical signs associated with pneumonia include:

General Pneumonia Symptoms:

  • Chest pain, especially while breathing deeply
  • Confusion and behavioural changes, especially in elderly patients
  • Persistent cough with thick yellow/greenish/bloody mucus
  • Fever with chills, sweats, headaches, and loss of appetite
  • Fatigue with low energy levels
  • Shortness of breath, even with little activity
  • Nausea, vomiting, or diarrhoea

Symptoms in Infants & Children:

  • Fever with coughing
  • Lack of interest in eating
  • Excessive crying, lethargy
  • Very fast breathing is visible in the ribcage

Symptoms in Older Adults:

  • Body temperature lower than normal
  • Pre-existing illnesses worsening
  • Mental confusion and behavioural changes

What Are the Types of Pneumonia?

The types of pneumonia include:

Depending on the Location of Acquisition:

  • Community-Acquired Pneumonia (CAP): People catch this common type of lung infection outside of hospitals and healthcare facilities.
  • Hospital-Acquired Pneumonia (HAP): Occurs in patients admitted to hospitals for some other illness. It involves more chronic diseases and antibiotic-resistant bacteria.
  • Healthcare-Associated Pneumonia (HCAP): Developed at nursing homes, dialysis centres, and clinics. Similar risks as HAP.
  • Ventilator-Associated Pneumonia (VAP): Occurs in people on ventilators due to compromised lung defence mechanisms.
  • Aspiration Pneumonia: Caused by inhaling food/drink into the lungs, seen in people with swallowing difficulties.

Depending on the Causative Agent:

  • Bacterial Pneumonia: The most common variety is triggered by bacteria like Streptococcus Pneumoniae, Staphylococcus aureus, and Mycoplasma pneumonia.
  • Viral Pneumonia: Caused by influenza, COVID-19, and respiratory syncytial virus (RSV). It is usually mild but can be fatal for certain groups.
  • Fungal Pneumonia: Seen in people with chronic diseases or weakened immunity due to fungi.
  • Protozoal Pneumonia: Rare pneumonia caused by protozoa like Toxoplasma.

Depending on the Pattern of Lung Inflammation:

  • Lobar Pneumonia: Infects one or more sections (lobes) of the lungs, common in bacterial cases.
  • Bronchopneumonia: Infects patches throughout both lungs, more common in viral infections.
  • Interstitial Pneumonia: Infects the interstitial tissue of the lungs.

Causes of Pneumonia

Pneumonia can occur due to various infectious pathogens as well as aspiration events such as:

Bacterial Causes

Bacteria are the most common infectious cause of pneumonia. Streptococcus Pneumoniae tops the list, causing up to 50% of pneumonia cases. This gram-positive bacteria has over 90 known serotypes that make it harder to develop universal vaccines against. It spreads via respiratory droplet transmission from carriers.

Other common bacterial pneumonia culprits are:

  • Staphylococcus Aureus: Mostly methicillin-resistant strains (MRSA) trigger healthcare-associated pneumonia in hospitals when immunity is lowered.
  • Mycoplasma Pneumoniae: Atypical bacteria lacking cell walls cause ‘Walking Pneumonia’ with milder symptoms. Common in school-aged children.
  • Chlamydophila Pneumoniae: Also an atypical bacteria, it is linked to gradually worsening symptoms when turning chronic and more challenging to diagnose.
  • Legionella Pneumophila: Gram-negative bacteria that colonise water reservoirs and infect lungs by inhaling droplets from air conditioning, humidifiers, and fountains.

Viral Causes

Viruses are the second most common cause of infectious pneumonia. Leading viral culprits are:

  • Influenza: Seasonal flu viruses damage airway linings every year and can turn fatal for high-risk groups. This includes influenza A, B and C strains.
  • COVID-19: The novel SARS-CoV-2 coronavirus caused waves of viral pneumonia with respiratory distress during the recent pandemic.
  • Respiratory Syncytial Virus (RSV): A common cause of pneumonia in infants and young kids, especially in winter months. 

Fungal Causes

Certain fungi can trigger pneumonia in immunocompromised people; these include:

  • Pneumocystis Jirovecii: This yeast-like fungus causes a form of pneumonia called PCP in HIV-positive people with very low T-cell counts.
  • Cryptococcus Neoformans: Found in soil, it can infect lung tissue, more fatal in organ transplant recipients on immunosuppressive therapy.
  • Histoplasma Capsulatum: Inhaling airborne spores of this dimorphic fungus can lead to acute lung infections.
  • Coccidioides Immitis and Coccidioides Posadasii: Also called valley fever or desert rheumatism, these soil fungi can cause community-acquired pneumonia when spores are stirred into the air.

Risk factors

People at higher risk for pneumonia include:

  • Age: Very young children and adults above 65 years
  • Hospitalised patients, especially those with chronic diseases
  • Lung diseases like COPD, asthma that affect airway clearance
  • Smoking and excessive alcohol consumption
  • Weak immune system due to HIV, organ transplant, chemotherapy
  • Taking food, liquids, or vomit into the lungs due to swallowing difficulties


As pneumonia symptoms can be vague, diagnostic tests are required to ascertain it. Hence, the diagnosis of pneumonia can include:

  • A physical examination checks vital parameters like temperature, blood pressure, and heart rate and also involves checking the chest with a stethoscope to listen to abnormal lung sounds.
  • Breathing and oxygenation tests are done using pulse oximetry, which measures oxygen saturation levels in the blood via a sensor probe.
  • Blood tests assess markers like white blood cell counts, which indicate infection when elevated. These help narrow down potential causative agents.
  • Microbiological testing involves taking sputum samples coughed out by the patient and analysing them. The presence of pathogenic bacteria or fungi confirms pneumonia. This also allows for testing antibiotic efficacy.
  • Imaging tests like chest X-rays and CT scans visualise the lungs and highlight areas of infection as opacities or inflamed spots. These also help track disease progression.
  • If there is fluid accumulation surrounding the lungs, known as pleural effusion, samples may be collected using a needle and sent for pleural fluid culture to confirm pneumonia diagnosis and design targeted treatment plans accordingly.
  • In some difficult cases, physicians may perform bronchoscopy by inserting an endoscope tube with a camera into the airways to view the lungs from inside and take fluid or tissue samples if required.

Treatment Procedures

The pneumonia treatment plan is customised as per the type identified from tests and the severity of the infection. Some options can include:

Bacterial Pneumonia Care: Antibiotics like Amoxicillin, Azithromycin, and Doxycycline depending on antibiotic sensitivity results.

Viral Pneumonia Care: Includes mostly symptomatic treatment – rest, fluids, fever/cough medication.

General Care

  • Cough suppressants, throat lozenges
  • Ibuprofen and Acetaminophen for pain and fever
  • Chest physiotherapy for mucus drainage
  • Oxygen support if blood oxygen levels are very low

In Severe Cases

  • Hospitalisation in ICU
  • IV antibiotic injections
  • Ventilator support
  • Pleural fluid drainage, if required

In most cases, pneumonia resolves within 1-3 weeks of medical treatment. Completing the entire course of antibiotics is essential, even if you start to feel better.

Prevention Tips

Some ways to prevent pneumonia infections include:

  • Get vaccinated against common pneumonia-causing agents like influenza, Streptococcus Pneumoniae, COVID-19
  • Practise good hygiene – cover mouth while sneezing or coughing, and wash hands regularly
  • Manage any chronic lung condition diligently with medical care
  • Improve immunity with a balanced diet and regular exercise


Pneumonia can result from various lung pathogens and can range from mild to fatal. Timely medical care guided by on-time diagnosis allows for appropriate treatment. One can also take preventive measures by limiting controllable risk factors and getting vaccinated. 

Creating awareness about pneumonia is key, especially among at-risk groups like infants and the elderly.