👉 Infections are a fundamental aspect of biological systems, representing the invasion and proliferation of pathogens—such as bacteria, viruses, fungi, or parasites—within a host organism. These pathogens breach the body's defenses, often exploiting vulnerabilities like weakened immunity or breaches in physical barriers (e.g., skin, mucous membranes). Once inside, they multiply, triggering immune responses that can lead to inflammation, tissue damage, or systemic illness. The severity of an infection depends on factors like pathogen virulence, host health, and the effectiveness of immune defenses. For example, a bacterial infection might cause fever and pus formation, while a viral infection could lead to cellular disruption and symptoms like fatigue. Understanding infections is critical for developing treatments, such as antibiotics for bacterial threats or antivirals for viral diseases, and for preventing spread through hygiene practices and vaccines.
