Which theory explains that microorganisms are the only cause of disease?

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2020

Explanation

The Germ Theory of disease, developed in the 19th century, was a revolutionary concept that shifted focus to microbes as the cause of disease.
Its central principle is a one-to-one relationship: a specific microorganism (agent) is the sole cause of a specific disease.
This theory is foundational to microbiology and the understanding of infectious diseases, moving away from earlier beliefs like 'bad air' (miasma theory).
The question's use of the phrase 'only cause' is the key identifier for the Germ Theory's single-agent model.

Option A: The Web of Causation theory posits that disease is caused by a complex network of multiple interacting factors, which is the opposite of a single-cause explanation.
Option B: The Multifactorial Causation theory explicitly states that disease results from multiple factors, not a single one like a microorganism.
Option D: The Epidemiological Triad theory requires the interaction of three components (Agent, Host, Environment) for disease to occur. It asserts that the agent (microorganism) is not the 'only' cause.

Clinical Relevance

Nursing practice connection: Knowing Theories of Disease Causation in Epidemiology helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding these theories is crucial for nursing practice, especially in community health and disease prevention.
Interventions based on Germ Theory focus on breaking the chain of infection: hand hygiene, sterilization, vaccination, and antibiotics.
Interventions based on multifactorial models focus on health education and lifestyle modification to reduce risk factors for chronic diseases (e.g., smoking cessation programs, dietary counseling).

How to Approach the Question

First, identify the key phrase in the question: 'microorganisms are the only cause'. The word 'only' is a strong qualifier.
Recall the basic principles of the main epidemiological theories of disease causation.
Evaluate each option against the key phrase.
Germ Theory: Proposes a single agent causes a single disease. This matches 'only cause'.
Web of Causation & Multifactorial Theory: Propose multiple causes. This contradicts 'only cause'.
Epidemiological Triad: Proposes three interacting components (Agent, Host, Environment). The agent is necessary but not sufficient ('only cause').

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart A (pp 26-201 of 604) pp. 24-26, 25-27

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Attempt every question from this paper in a timed mock, then review the full solution for each one.