In the chain of infection model, which sequence of events correctly describes how an infection occurs?

• A. Reservoir → infectious agent → susceptible host → mode of transmission → portal of exit → portal of entry
• B. Infectious agent → reservoir → portal of exit → mode of transmission → portal of entry → susceptible host
• C. Mode of transmission → reservoir → portal of entry → portal of exit → susceptible host → infectious agent
• D. Susceptible host → portal of entry → portal of exit → reservoir → infectious agent → mode of transmission

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the components of the chain of infection. The chain includes: infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host.
2. Step 2: Recognize the correct order in which an infection occurs. It starts with the infectious agent (the pathogen causing disease).
3. Step 3: The infectious agent must have a reservoir, which is the natural habitat where it lives and multiplies (e.g., humans, animals, environment).
4. Step 4: The infectious agent leaves the reservoir through a portal of exit (such as respiratory secretions, blood, or skin).
5. Step 5: The agent is then transmitted via a mode of transmission (direct contact, airborne, vector-borne, etc.) to enter a new host through a portal of entry (like mucous membranes or broken skin), finally reaching a susceptible host who can become infected.