What initiates the process of infection?

The process of infection begins with a pathogen, which is any microorganism capable of causing disease. Pathogens include a wide range of infectious agents such as bacteria, viruses, fungi, and parasites. When a pathogen enters a host's body and starts to multiply, it can overwhelm the host’s immune defenses, leading to an infection.

While viruses and bacteria are specific types of pathogens, they cannot initiate the infection process on their own without being classified as pathogens. Antibiotics are substances used to treat infections caused by bacteria and do not initiate infections; instead, they work to eliminate pathogens that have already caused an infection. The fundamental concept is that all infections are initiated by pathogens, making this the most accurate choice in the context of what triggers infection.