Source of Infection: The origin of the infectious agent, which could be an infected individual, animal, or contaminated environment. Portal of Exit: The pathway through which the infectious agent leaves the host, such as respiratory secretions, feces, blood, or skin lesions. Mode of Transmission: The method by which the infectious agent is transferred to a new host, as discussed earlier. Portal of Entry: The route through which the infectious agent enters the new host, such as through inhalation, ingestion, or breaks in the skin. Susceptible Host: An individual who lacks immunity or resistance to the infectious agent and is therefore vulnerable to infection.
