What is the most common etiologic category of pneumonia in children under 5?

• A. Bacterial infection
• B. Fungal infection
• C. Parasitic infection
• D. Viral infection

Answer: (D)

The main idea is that viral infections are the leading cause of pneumonia in children under five. In this age group, the respiratory tract is very susceptible to viral infections, and viruses such as RSV, rhinovirus, influenza, parainfluenza, and adenovirus commonly cause pneumonia or viral bronchiolitis with pneumonia features. Bacterial pneumonia does occur but is less common overall in young children and often presents with distinct signs like higher fever and focal chest findings suggesting lobar consolidation, which can be harder to differentiate from viral disease. Fungal and parasitic pneumonias are rare in healthy kids. Because viruses predominate, many episodes of pneumonia in under-fives are viral, and management focuses on supportive care with antibiotics used more selectively when bacterial pneumonia is suspected.