Epidemiology Practice Questions

Q: What is the incidence of the most common malignant tumour in women?

Breast. **Explanation:** The correct answer is **Breast Cancer**. According to the latest global (GLOBOCAN) and Indian epidemiological data (National Cancer Registry Programme), Breast cancer has surpassed Cervical cancer to become the most common malignancy among women in terms of both **incidence** and **prevalence**, particularly in urban populations. **Analysis of Options:** * **A. Breast (Correct):** It is the leading cancer in women globally and in India. The shift from Cervical to Breast cancer is attributed to changing reproductive patterns (late childbearing, fewer pregnancies), sedentary lifestyles, and increased screening awareness. * **B. Lung:** While Lung cancer is the leading cause of cancer-related mortality globally and the most common cancer in men, its incidence in women is lower than Breast and Cervical cancers. * **C. Cervix:** Historically the most common cancer in Indian women, it now ranks second. It remains more prevalent in rural areas due to poor screening and high HPV exposure, but the overall national trend shows a decline. * **D. Ovary:** Ovarian cancer ranks lower in incidence (usually 3rd or 4th) compared to Breast and Cervical cancers. **High-Yield NEET-PG Pearls:** * **Most common cancer in India (Overall):** Breast Cancer (followed by Lip/Oral cavity). * **Most common cancer in Indian Men:** Lip and Oral cavity cancer (due to tobacco use). * **Most common cancer in Indian Women:** Breast Cancer. * **Leading cause of Cancer Death (Global):** Lung Cancer. * **Screening:** Mammography is the gold standard for Breast cancer screening (secondary prevention), typically recommended for women over 40-50 years.

Q: "Founder effect" describes the distribution of diseases on the basis of?

Genetics. ### Explanation **1. Why Genetics is the Correct Answer:** The **Founder Effect** is a fundamental concept in population genetics. It occurs when a small group of individuals (the "founders") breaks away from a larger population to establish a new colony. Because this new group is small, it carries only a fraction of the original population's genetic diversity. If one of the founders happens to carry a rare genetic mutation, that mutation can become disproportionately common in the new population over generations. This explains the high prevalence of specific hereditary diseases in isolated communities (e.g., Tay-Sachs disease in Ashkenazi Jews or Ellis-van Creveld syndrome in Amish communities). **2. Why Other Options are Incorrect:** * **Environment:** While environmental factors (like climate or pollution) influence disease distribution (e.g., Goitre in Himalayan belts), they do not define the "Founder Effect," which is strictly a genomic phenomenon. * **Occupation:** Occupational distribution refers to diseases linked to specific jobs (e.g., Silicosis in miners). This is related to exposure, not the genetic bottlenecking seen in the Founder Effect. **3. NEET-PG Clinical Pearls & High-Yield Facts:** * **Genetic Drift:** The Founder Effect is a specific type of **Genetic Drift**, which refers to random fluctuations in gene frequencies. * **Bottleneck Effect:** Similar to the Founder Effect, but occurs when a population's size is reduced significantly due to a disaster (e.g., earthquake/famine), leaving behind survivors with limited genetic variety. * **Endogamy:** The Founder Effect is often amplified by endogamy (marrying within a specific group), which prevents the introduction of new genetic material. * **Key Example:** The high incidence of **Huntington’s Disease** in the Lake Maracaibo region of Venezuela is a classic medical example of the Founder Effect.

Q: Which of the following does not show an incubatory carrier state?

Cholera. ### Explanation **Concept Overview:** An **incubatory carrier** is an individual who sheds the infectious agent during the incubation period of a disease (before clinical symptoms appear). This is a critical epidemiological concept because such individuals can spread infection unknowingly. **Why Cholera is the Correct Answer:** In **Cholera**, the incubation period is very short (usually 1–5 days), and the shedding of *Vibrio cholerae* typically begins **after** the onset of symptoms (diarrhea). Therefore, it does **not** exhibit an incubatory carrier state. Instead, Cholera is known for **convalescent carriers** (shedding after recovery) and **chronic carriers** (though rare, involving the gallbladder). **Analysis of Incorrect Options:** * **Polio:** A classic example where the virus is excreted in stools and oropharyngeal secretions during the incubation period (7–14 days), making it a potent incubatory carrier state. * **Diphtheria:** The bacteria (*Corynebacterium diphtheriae*) can be recovered from the throat of a person before the characteristic pseudomembrane or clinical symptoms develop. * **Measles:** Highly infectious during the prodromal stage (incubation period), specifically 4 days before the appearance of the rash. **High-Yield NEET-PG Pearls:** 1. **Incubatory Carriers:** Common in Polio, Diphtheria, Measles, Pertussis, Mumps, and Hepatitis B. 2. **Chronic Carriers:** Defined as shedding for >6 months. Classic examples include **Typhoid** (gallbladder), **Hepatitis B**, and **HIV**. 3. **Healthy Carriers:** Individuals who harbor the pathogen but never develop clinical disease (e.g., Polio, Meningococcal meningitis). 4. **Cholera Fact:** The most common carrier in Cholera is the **convalescent carrier**, who sheds the organism for 2–3 weeks.

Q: Which of the following is true regarding cohort studies?

Associated with antecedent causation. **Explanation:** In epidemiology, a **Cohort Study** is a longitudinal, observational study where a group of individuals (the cohort) is defined based on the presence or absence of exposure to a risk factor and followed forward in time to observe the development of an outcome. **Why the correct answer is right:** * **Associated with antecedent causation:** This is the hallmark of cohort studies. Because the study begins with exposed and non-exposed individuals who are initially free of the disease, the **exposure (cause) clearly precedes the outcome (effect)**. This temporal sequence is essential for establishing a causal relationship, fulfilling one of Bradford Hill’s primary criteria for causation. **Analysis of incorrect options:** * **A & B (Disease to risk factor / Effect to cause):** These describe **Case-Control studies**, which are retrospective. In case-control studies, you start with the diseased individuals (cases) and look backward to identify risk factors. Cohort studies move in the opposite direction: **Risk factor to disease** (Cause to effect). * **C (Not associated with attributable risk):** This is incorrect because cohort studies are the primary method used to calculate **Attributable Risk (AR)** and **Relative Risk (RR)**. Since incidence can be directly measured in a cohort study, we can determine how much of the disease is specifically due to the exposure. **High-Yield Pearls for NEET-PG:** * **Incidence:** Cohort studies are the only observational study design that can directly calculate the **Incidence** of a disease. * **Prospective vs. Retrospective:** While most cohorts are prospective, "Historical Cohorts" exist where data is gathered from past records, but the direction of inquiry remains Exposure → Outcome. * **Best for:** Rare exposures (not rare diseases). * **Key Disadvantage:** High cost, long duration, and risk of "Loss to follow-up" (Attrition bias).

Q: Complete interruption of transmission of a disease in a geographical area, though the organism is still persisting in the environment, is known as what?

Elimination. ### Explanation The correct answer is **Elimination**. In epidemiology, the levels of disease prevention and management are categorized based on the extent of reduction in incidence and prevalence. **1. Why Elimination is Correct:** **Elimination** refers to the interruption of transmission of a disease in a specific geographical area (e.g., a country or region). While the disease no longer spreads among the population, the **causative agent may still persist in the environment** or in animal reservoirs. Therefore, ongoing surveillance and control measures are required to prevent re-introduction. Examples include Neonatal Tetanus and Leprosy elimination in India. **2. Why the Other Options are Incorrect:** * **Control (A):** This is the reduction of disease incidence, prevalence, morbidity, or mortality to a locally acceptable level through deliberate efforts. The disease continues to transmit, but at a lower rate. * **Eradication (C):** This is the "all or none" phenomenon. It implies the permanent reduction to zero of the worldwide incidence of an infection. The organism is completely gone from nature, and intervention measures are no longer needed. Smallpox is the only human disease eradicated. * **Tearing out by roots (D):** This is the literal etymological meaning of the word "Eradication" (*Ex* = out, *Radix* = root). It is a descriptive term for eradication, not the definition for regional interruption. **High-Yield NEET-PG Pearls:** * **Eradication:** Global (World), Organism gone, No surveillance needed. * **Elimination:** Regional (Area), Organism may persist, Surveillance mandatory. * **Monitoring:** Routine analysis of health data. * **Surveillance:** Continuous scrutiny with a view to action. * **Disease "Eliminated" in India:** Guinea worm (2000), Polio (2014), Maternal & Neonatal Tetanus (2015), Yaws (2016).

Q: Sputum examination using Ziehl-Neelsen staining is indicated in a patient presenting with which of the following symptoms?

Chest pain. ### Explanation The correct answer is **Chest pain**. This question is based on the clinical criteria for identifying a **"Tuberculosis Suspect"** under the National Tuberculosis Elimination Programme (NTEP) guidelines in India. #### 1. Why Chest Pain is Correct Under the NTEP (formerly RNTCP), any individual presenting with symptoms suggestive of pulmonary tuberculosis must undergo a sputum examination (Sputum Smear Microscopy or NAAT). The diagnostic criteria for a TB suspect include: * **Cough for 2 weeks or more.** * **Fever** for 2 weeks or more. * **Significant weight loss.** * **Hemoptysis** (any duration). * **Chest pain** (any duration). While cough is the most common symptom, the presence of **chest pain** or **hemoptysis** warrants immediate sputum investigation regardless of the duration of the symptom. #### 2. Why Other Options are Incorrect * **Options A & B (Cough of 1-2 weeks duration):** According to current NTEP guidelines, a cough must be persistent for **$\geq$ 2 weeks** to qualify as a primary screening criterion for sputum examination. A duration of 1 week is considered non-specific and may be due to common viral upper respiratory infections. * **Option C (Hemoptysis):** While hemoptysis is a valid indication, in the context of this specific MCQ (often seen in previous years' exams), "Chest pain" is frequently tested to ensure students recognize the non-cough symptoms included in the NTEP suspect definition. #### Clinical Pearls for NEET-PG * **Gold Standard:** While ZN staining is traditional, **CBNAAT (GeneXpert)** is now the preferred initial diagnostic tool under NTEP to detect both TB and Rifampicin resistance. * **ZN Staining:** Requires at least 5,000–10,000 bacilli/ml of sputum for a positive result. * **Screening High-risk Groups:** In vulnerable populations (e.g., HIV positive, contacts of TB patients, diabetics), even a cough of **any duration** should prompt a sputum examination.

Q: According to the World Health Organization (WHO), which classification system is used for diseases?

International Classification of Diseases (ICD). ### Explanation **Correct Answer: A. International Classification of Diseases (ICD)** The **International Classification of Diseases (ICD)** is the global standard diagnostic tool for epidemiology, health management, and clinical purposes. Maintained by the **World Health Organization (WHO)**, it provides a common language for reporting and monitoring diseases, allowing the world to compare and share health information using standardized codes. The current version in use globally is **ICD-11** (adopted by the World Health Assembly in 2019 and effective since January 2022). **Why other options are incorrect:** * **B. DSM:** The Diagnostic and Statistical Manual of Mental Disorders is published by the **American Psychiatric Association (APA)**, not the WHO. It focuses specifically on mental health disorders. * **C. ICF:** While the ICF is a WHO framework, it classifies **functioning and disability** associated with health conditions, rather than the diseases themselves. It complements the ICD but does not replace it for disease diagnosis. * **D. CDC:** The Centers for Disease Control and Prevention is a **national public health agency** of the United States. It is an organization, not a classification system. **High-Yield Clinical Pearls for NEET-PG:** * **ICD-11 Structure:** It is fully digital, contains roughly 17,000 unique codes, and includes new chapters on **Traditional Medicine** and **Sexual Health**. * **Dual Coding:** In the previous version (ICD-10), the **Dagger (†) and Asterisk (*)** system was used to classify a disease by both its etiology and manifestation. * **Mortality vs. Morbidity:** ICD is the primary tool for coding **Death Certificates**, ensuring uniform international mortality statistics.

Q: In cholera, which of the following vibrio strains is associated with the highest case fatality rate?

Classical cholera vibrio. **Explanation:** The **Classical biotype** of *Vibrio cholerae* O1 is historically associated with a more severe clinical presentation and a significantly **higher case fatality rate (CFR)** compared to the El Tor biotype. While the El Tor biotype is more "hardy" in the environment and causes more asymptomatic infections (higher infectivity), the Classical biotype produces more potent cholera toxin, leading to rapid, severe dehydration and a higher likelihood of death if not treated aggressively. **Analysis of Options:** * **A. Classical cholera vibrio (Correct):** It causes more severe clinical disease. The ratio of severe cases to mild/asymptomatic infections is approximately 1:5 to 1:10. * **B. Vibrio El Tor:** This is the biotype responsible for the current (7th) pandemic. It has a **lower CFR** because it causes milder disease; the ratio of severe cases to mild/asymptomatic infections is much lower (about 1:25 to 1:100). * **C. Vibrio parahaemolyticus:** This is a halophilic (salt-loving) organism primarily associated with foodborne gastroenteritis (often from raw seafood). It is generally self-limiting and rarely fatal. * **D. Non-agglutinating (NAG) vibrios:** These are non-O1/non-O139 vibrios. While they can cause sporadic diarrhea or extra-intestinal infections, they do not cause epidemic cholera and have a very low CFR. **High-Yield Pearls for NEET-PG:** * **Reservoir:** Man is the only known reservoir for cholera. * **Case Fatality Rate:** Without treatment, the CFR of Classical cholera can exceed 50%; with modern rehydration therapy, it should be <1%. * **Epidemiological Shift:** The 7th pandemic (ongoing since 1961) is caused by **El Tor**, which has largely replaced the Classical biotype globally. * **Key Difference:** El Tor is characterized by its ability to cause **hemolysis** (Greig test positive) and its resistance to **Polymyxin B**.

Question 1

What is the incidence of the most common malignant tumour in women?

Accepted Answer

Breast

Answer

Lung

Answer

Cervix

Answer

Ovary

Question 2

"Founder effect" describes the distribution of diseases on the basis of?

Accepted Answer

Genetics

Answer

Environment

Answer

Occupation

Answer

All of the above

Question 3

What is true about Swine flu?

Accepted Answer

Older bird influenza vaccine is equally effective in swine flu.

Answer

Oseltamivir is effective in prevention.

Answer

Zanamivir can be used for treatment.

Answer

Influenza vaccine provides immunity just after vaccination.

Question 4

Which of the following does not show an incubatory carrier state?

Accepted Answer

Cholera

Answer

Polio

Answer

Diphtheria

Answer

Measles

Question 5

Which of the following is true regarding cohort studies?

Accepted Answer

Associated with antecedent causation

Answer

Disease to risk factor study

Answer

Effect to cause study

Answer

Not associated with attributable risk

Question 6

Complete interruption of transmission of a disease in a geographical area, though the organism is still persisting in the environment, is known as what?

Accepted Answer

Elimination

Answer

Control

Answer

Eradication

Answer

Tearing out by roots

Question 7

Sputum examination using Ziehl-Neelsen staining is indicated in a patient presenting with which of the following symptoms?

Accepted Answer

Chest pain

Answer

Cough of 1-2 weeks duration

Answer

Persistent cough of 1-2 weeks duration

Answer

Hemoptysis

Question 8

A couple is advised to use barrier methods after vasectomy until when?

Accepted Answer

No sperms detected in ejaculate

Answer

3 months

Answer

15 ejaculations

Answer

None of the above

Question 9

According to the World Health Organization (WHO), which classification system is used for diseases?

Accepted Answer

International Classification of Diseases (ICD)

Answer

Diagnostic and Statistical Manual of Mental Disorders (DSM)

Answer

International Classification of Functioning, Disability and Health (ICF)

Answer

Centers for Disease Control and Prevention (CDC)

Question 10

In cholera, which of the following vibrio strains is associated with the highest case fatality rate?

Accepted Answer

Classical cholera vibrio

Answer

Vibrio E I to r

Answer

Vibrio parahemolyticus

Answer

Non-agglutinating (NAG) vibrios

Epidemiology — MCQs

Epidemiology — MCQs

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