In the chain of infection model, which sequence of events correctly describes how an infectious disease is transmitted and leads to infection in a new host?

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

Answer: (A)

Verified step by step guidance

1. Understand that the chain of infection describes the sequence of events that allow an infectious disease to spread from one host to another.
2. Identify the six key components in the chain: infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host.
3. Recognize that the infectious agent (such as bacteria or viruses) must first be present in a reservoir, which is the natural habitat where the agent lives and multiplies.
4. Next, the infectious agent leaves the reservoir through a portal of exit (like respiratory secretions or blood), then travels via a mode of transmission (such as direct contact, droplets, or vectors).
5. Finally, the agent enters a new host through a portal of entry (like mucous membranes or broken skin), and if the host is susceptible, infection can occur.