Epidemiology — MCQs

Epidemiology Indian Medical PG Practice Questions and MCQs

Question 1901: Multifactorial causation of disease theory was proposed by whom?

A. Pettenkofer (Correct Answer)
B. Aristotle
C. Robert Koch
D. Louis Pasteur

Explanation: ***Pettenkofer*** - **Pettenkofer** is associated with the idea that while a germ might be present, other **environmental factors** and host conditions play a crucial role in disease development. - He proposed that a specific **cause** was not sufficient by itself to produce disease, highlighting the importance of multiple contributing factors. *Louis Pasteur* - **Louis Pasteur** is famous for his work on the **germ theory of disease**, demonstrating that microorganisms cause disease. - His contributions primarily focused on identifying specific pathogens for specific diseases, which is a **unifactorial approach** rather than multifactorial. *Robert Koch* - **Robert Koch** further solidified the **germ theory** with his postulates, establishing criteria to prove that a specific organism causes a specific disease. - His work was also centered on identifying single causative agents, contrasting with the **multifactorial causation** theory. *Aristotle* - **Aristotle** was an ancient Greek philosopher who contributed to many fields, including early biological observations, but his theories predate modern understanding of disease causation. - He did not propose a modern **multifactorial causation of disease theory**; his work was foundational but not specific to this concept.

Question 1902: Vector of trench fever is which one of the following?

A. Louse (Correct Answer)
B. Tick
C. Mite
D. Rat flea

Explanation: ***Louse*** - **Trench fever** is caused by the bacterium *Bartonella quintana* and is primarily transmitted to humans by the **body louse** (*Pediculus humanus corporis*). - The disease became notorious during World War I due to its prevalence among soldiers living in crowded, unhygienic conditions, which favored louse infestation. *Tick* - Ticks are vectors for various diseases such as **Lyme disease**, **Rocky Mountain spotted fever**, and **Ehrlichiosis**, but not trench fever. - These diseases are caused by different bacterial species and present with distinct clinical manifestations. *Mite* - Mites are known vectors for diseases like **scrub typhus** (transmitted by chiggers) and can cause conditions such as **scabies**, but they do not transmit trench fever. - Mites typically live on or in the skin of their hosts, and their biting patterns and associated pathogens differ from those of lice. *Rat flea* - **Rat fleas** (*Xenopsylla cheopis*) are the primary vectors for **bubonic plague** (caused by *Yersinia pestis*) and **murine typhus** (caused by *Rickettsia typhi*). - These diseases are distinct from trench fever in their causative agents, transmission cycles, and clinical presentations.

Question 1903: Which of the following diseases is not transmitted by lice?

A. Relapsing fever
B. Trench fever
C. Q fever (Correct Answer)
D. Epidemic typhus

Explanation: ***Correct: Q fever*** - **Q fever** is caused by *Coxiella burnetii* and is primarily transmitted by **inhalation of aerosols** from infected animal products or excretions, not by lice - Exposure to infected livestock (cattle, sheep, goats) or their birth products is the most common route of transmission - This is a zoonotic disease with no arthropod vector involvement *Incorrect: Relapsing fever* - Louse-borne relapsing fever is caused by *Borrelia recurrentis* and transmitted by the body louse (*Pediculus humanus corporis*) - Infection occurs when infected lice are crushed, releasing bacteria into breaks in the skin - Characterized by recurrent episodes of fever, prevalent in areas with poor hygiene and overcrowding *Incorrect: Trench fever* - Caused by *Bartonella quintana* and transmitted by the body louse (*Pediculus humanus corporis*) through its feces - Infection occurs when louse feces are scratched into the skin or mucous membranes, or when inhaled - Associated with homelessness, overcrowding, and poor hygiene *Incorrect: Epidemic typhus* - Caused by *Rickettsia prowazekii* and transmitted by the body louse when its feces containing bacteria are rubbed into abraded skin or mucous membranes - Associated with poor hygiene and crowded conditions, particularly during wars, disasters, or refugee situations - Can cause severe systemic illness with high fever and rash

Question 1904: What is the primary limitation of conducting a one-day census of inpatients in a mental hospital?

A. Provides a snapshot of the current patient demographic but lacks longitudinal data. (Correct Answer)
B. Gives reliable estimates of seasonal factors in admissions.
C. Allows for conclusions about the overall mental health trends in India.
D. Enables estimation of the distribution of different diagnoses over time.

Explanation: ***Provides a snapshot of the current patient demographic but lacks longitudinal data.*** - A **one-day census** inherently captures data from a single point in time, offering a **"snapshot"** of the inpatient population on that specific day. - This method cannot provide information about changes in patient demographics, diagnoses, or treatment outcomes **over time**, which is essential for understanding trends and the effectiveness of interventions. *Gives reliable estimates of seasonal factors in admissions.* - A **single-day census** cannot provide reliable information about **seasonal variations** in admissions because it does not include data across different time periods. - Understanding seasonal factors requires data collected over a **longer duration**, typically spanning multiple seasons or a full year. *Allows for conclusions about the overall mental health trends in India.* - A census from a **single mental hospital** on one day provides highly localized data and cannot be extrapolated to represent **overall mental health trends** for an entire country like India. - Such broad conclusions require **nationwide epidemiological studies** with representative samples. *Enables estimation of the distribution of different diagnoses over time.* - A one-day census, by its very nature, provides data on the distribution of diagnoses only for that specific day, not **over time**. - To estimate changes in diagnostic distribution, **repeated censuses** or continuous data collection over an extended period would be necessary.

Question 1905: A drug that does not cure a disease but decreases its symptoms and increases survival leads to increased:

A. Increased incidence
B. Decreased prevalence
C. Decreased incidence
D. Increased prevalence (Correct Answer)

Explanation: ***Increased prevalence*** - A drug that **decreases symptoms** and **increases survival** means people live longer with the disease. - This leads to more existing cases at any given time, thus **increasing prevalence**. *Increased incidence* - **Incidence** refers to the rate of new cases of a disease in a population over a specific period. - A drug that *palliates* symptoms and increases survival does not affect the rate at which new cases develop; therefore, it does not alter incidence. *Decreased prevalence* - **Decreased prevalence** would occur if fewer people had the disease or if people recovered or died more quickly. - Since the drug *increases survival*, it would lead to more people living with the disease for longer, thus increasing, not decreasing, prevalence. *Decreased incidence* - **Decreased incidence** means fewer new cases are occurring. - A palliative drug that extends life does not prevent new cases from arising and therefore does not decrease incidence.

Question 1906: Which of the following attributes are essential for an ideal screening test?

A. Safe
B. Reliable
C. Valid
D. All of the options (Correct Answer)

Explanation: ***All of the options*** - An ideal screening test must possess **all three essential attributes**: safety, reliability, and validity. - **Safe**: Minimizes harm to participants and ensures ethical implementation - **Reliable**: Produces consistent, reproducible results with minimal random error - **Valid**: Accurately measures what it intends to measure (high sensitivity and specificity) - These three attributes work together as fundamental requirements for any effective screening program, ensuring that early detection benefits outweigh potential risks. *Safe (alone)* - While safety is absolutely essential, it is **not sufficient by itself** to make an ideal screening test. - A test that is safe but unreliable or invalid would produce inconsistent or inaccurate results, rendering it ineffective for screening purposes. *Reliable (alone)* - Reliability ensures consistent results, which is crucial, but **reliability alone is insufficient**. - A test can be highly reliable (consistently giving the same result) yet completely invalid if it measures the wrong thing or is unsafe. *Valid (alone)* - Validity is critical for accurate measurement, but **validity alone does not make a test ideal**. - Even a valid test must be safe to protect participants and reliable to ensure consistency across different settings and times.

Practice by Chapter

Principles of Epidemiology

Practice Questions

Measures of Disease Frequency

Practice Questions

Epidemiological Study Designs

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Descriptive Epidemiology

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Analytical Epidemiology

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Experimental Epidemiology

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Screening for Disease

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Surveillance Systems

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Investigation of an Epidemic

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Association and Causation

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Modern Epidemiological Methods

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Critical Appraisal of Epidemiological Studies

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