Final answer:
The transmission of microorganisms from person to person resulting in infection is known as contagion, and diseases that spread in this manner are considered contagious diseases.
Step-by-step explanation:
The transmission of microorganisms from person to person resulting in infection is called contagion. This form of pathogen spread happens through various modes including direct touch, where an infected person passes the microorganism to a non-infected person either by physical contact or by touching objects that are then touched by others. An infectious disease that easily spreads from person to person is considered a contagious disease, and the severity of its contagion depends on the method of transmission. For example, airborne diseases can spread through coughs or sneezes, while others might require close personal or sexual contact.