Pneumonia, a serious inflammatory condition of the lungs, is a leading cause of death in Singapore and worldwide.

Pneumonia accounted for 20.7 per cent of deaths in Singapore in 2019, just behind cancer, the top killer, which caused 28.4 per cent of deaths, according to the Ministry of Health (MOH).

What is pneumonia?

In pneumonia, the air-filled tiny sacs in the lungs get inflamed. These sacs, called alveoli, fill with pus and other fluids, making it difficult for oxygen to reach the blood and be transported everywhere in the body. This lung inflammation is usually caused by an infection.

Pneumonia can affect one or both lobes of the lungs. This correlates with the severity of the disease and it is also dependent on the cause of pneumonia. For example, viral pneumonia tends to involve a few lobes (called diffuse) whereas bacterial tends to be more localised unless it is severe, in which case a few lobes can be involved.

“Infants and young children, people over the age of 65, and people with chronic diseases such as chronic obstructive pulmonary disease, diabetes, cancer and heart disease, are at greatest risk of developing severe pneumonia which can be life-threatening,” says Associate Professor Loo Chian Min, Senior Consultant from the ​Department of Respiratory and Critical Care Medicine at Singapore General Hospital (SGH), a member of the SingHealth​ group.

Pneumonia causes and risk factors

Pneumonia is usually caused by infection from the following organisms:

  • Bacteria: The most common type is Streptococcus pneumoniae, followed by Haemophilus influenzae and other bacteria like Escherichia coli and Klebsiella pneumoniae. Infection from Mycoplasma pneumoniae, a bacteria-like organism, typically produces mild symptoms. This milder pneumonia is referred to as ‘walking pneumonia’ because it does not require bed rest.
  • Viruses: These are viruses similar to those causing common cold and influenza. Viral pneumonia is usually mild and is common in small children. Occasionally they may be severe and cause life threatening infection, like MERS-CoV (Middle East Respiratory Syndrome), Influenza H5N1 (bird flu), influenza H1N1, and the recent COVID-19 (Coronavirus Disease 2019).
  • Fungi: Fungi spores can be inhaled and cause infection in people with an underlying health problem or a weak immune system. It is uncommon in normal individuals.

A pneumonia infection can be contracted in the community (community-acquired pneumonia) or during a hospital or healthcare facility stay (hospital-acquired or healthcare-associated pneumonia). Patients who have prolonged hospital stay and those who are supported with ventilators are at a higher risk of developing hospital-acquired pneumonia.

You can also develop pneumonia when you inhale food, drink, or harmful chemicals into your lungs – this is known as aspiration pneumonia. This aspiration can happen because of a brain injury, a problem with swallowing, or excessive consumption of alcohol or drugs.

Pneumonia symptoms

Pneumonia symptoms vary depending on the cause, age of the patient, and the severity of the condition. Common pneumonia symptoms in adults are:

  • Cough with phlegm
  • Breathing difficulty
  • Chest pain
  • Body and muscle pain
  • Fever, chills
  • Headache

“In bacterial pneumonia, the cough produces thick greenish/yellowish phlegm while in viral pneumonia, the phlegm is white or clear,” says A/Prof Loo. “A patient suffering from bacterial pneumonia usually presents with a sudden onset of symptoms and high-grade fever.”

Pneumonia symptoms in children

  • Sudden onset of fever
  • Cough
  • Laboured and rapid breathing
  • Wheezing
  • Difficulty eating
  • Vomiting
  • Bluish skin, lip or fingertips
  • Fatigue

Read on to learn about the treatments and prevention of pneumonia​.

Ref: L20

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Adult Asthma: Frequently Asked Questions

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What is Chronic Obstructive Pulmonary Disease (COPD)?

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