What is meant by infection?

Infection refers specifically to the invasion of body tissues by pathogenic organisms, particularly bacteria, viruses, fungi, or parasites. When these harmful pathogens enter the body, they can begin to multiply and disrupt normal bodily functions, leading to various symptoms and illnesses. This process signifies a negative interaction where the pathogens may evade the immune system, causing harm to the host.

Understanding infection in this context is crucial for recognizing the importance of sanitation and disinfection practices. These practices are designed to eliminate pathogenic organisms, preventing their entry into the body and subsequent infections. The other choices describe different concepts: exposure to non-pathogenic organisms does not result in an infection; removal of foreign substances refers to detoxification or clearance mechanisms of the body, rather than an infection; and an immune response is a reaction by the body's immune system to combat infections, rather than the infection itself.