INFECTIOUS DISEASES

Infectious diseases are caused by pathogenic microorganisms that invade and replicate within the host, producing a broad spectrum of clinical manifestations ranging from mild localized infections to severe systemic and life-threatening illness. This chapter provides an overview of infectious disease pathophysiology, pathogen classification, routes of transmission, and host susceptibility factors. Common bacterial, viral, and parasitic diseases are discussed along with essential concepts related to antimicrobial therapy and the growing challenge of antimicrobial resistance. Infection-control principles—including standard and transmission-based precautions—are highlighted to emphasize prevention within healthcare and community environments. The chapter also outlines the critical nursing role in surveillance, medication administration, patient education, and containment strategies. Understanding infectious diseases is fundamental for clinical decision-making, public health planning, outbreak response, and global health security.