Raj. CHO -2025: What is the correct sequence of the 'chain of infection'?

Raj. CHO -2025

Applied Microbiology & Infection control

Easy

Appeared in: Raj. CHO -2025

Explanation

The chain of infection model requires a specific, logical order for a pathogen to spread successfully.
The process must begin with an infectious agent (the germ) residing in a reservoir (its home).
The agent must then have a way to leave the reservoir (portal of exit) before it can be transmitted (mode of transmission).
Finally, it must find a way into a new host (portal of entry) who is susceptible to the disease.
This sequence is the only one that logically describes the complete journey of a pathogen from one source to another.

Option B: This option incorrectly places the 'Infectious agent' and 'Reservoir' in the middle of the chain. The process must start with the agent and its source.
Option C: This option incorrectly places the 'Portal of entry' before the 'Portal of exit' and ends with the 'Infectious agent'. A pathogen must exit its source before it can enter a new host, and the agent is the starting point, not the end.
Option D: This option incorrectly places the 'Susceptible host' early in the chain, before the pathogen has even left its original reservoir. The susceptible host is the final link in the chain.

Visual 1: Flowchart - A circular diagram illustrating the six links of the chain of infection in order, with arrows showing the cyclical nature of the process.
Visual 2: Infographic - An infographic that pairs each link of the chain with a corresponding nursing intervention to 'break the chain' (e.g., Hand Hygiene next to Mode of Transmission, Vaccination next to Susceptible Host).

Clinical Relevance

Nursing practice connection: Safe nursing care depends on performing The sequence of events in the chain of infection in the correct sequence, documenting the action clearly, and monitoring for the expected response.
Understanding the chain of infection is the foundation of all infection control practices in nursing.
Nurses use this model to identify risks and implement targeted interventions. For example, placing a patient with tuberculosis in a negative pressure room breaks the chain at the 'Mode of Transmission' link (airborne).
Patient education about hand hygiene, food safety, and vaccination is a key nursing role derived directly from this model.

How to Approach the Question

This is a process-based recall question that tests your knowledge of a fundamental concept in infection control.
First, identify the key components: the six links of the chain of infection.
Think logically about how an infection must spread. It must start with a 'cause' (the agent) in a 'place' (the reservoir).
Follow the path: the agent must get out (exit), travel (transmission), and get in (entry) to a new person (host).
Evaluate each option against this logical sequence. Eliminate options that present an illogical order, such as the pathogen entering a new host before it has left the old one.

Concept Tested & Keywords

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Textbook of Applied Microbiology Including Infection Control and Safety (Second Edition) p. 255-256