Epidemiology — MCQs

Epidemiology Indian Medical PG Practice Questions and MCQs

Question 1771: Which of the following viral diseases is least commonly reported in India?

A. Japanese B encephalitis
B. Lassa fever (Correct Answer)
C. KFD
D. Dengue

Explanation: ***Lassa fever*** - **Lassa fever** is endemic to West Africa, with the **multimammate rat** being its primary reservoir. - Cases of Lassa fever are **extremely rare** in India, primarily limited to travel-related instances due to the geographical distribution of the disease and its vector. *Japanese B encephalitis* - **Japanese B encephalitis (JBE)** is a significant public health concern in India, particularly in endemic regions. - It is a mosquito-borne viral disease, and **vaccination programs** are ongoing to control its spread. *KFD* - **Kyasanur Forest Disease (KFD)** is an endemic viral hemorrhagic fever primarily found in the **Karnataka state of India**. - It is transmitted by **ticks**, making it a regionally significant but recognized viral disease within India. *Dengue* - **Dengue** is one of the most commonly reported and widespread viral diseases in India. - It is a **mosquito-borne** illness with frequent outbreaks occurring across various parts of the country.

Question 1772: In the context of demographic studies, how is 'population explosion' defined in terms of growth rate?

A. > 2% (Correct Answer)
B. 0.5% - 1.0%
C. 1.5% - 2.0%
D. 1.0% - 1.5%

Explanation: ***> 2%*** - A **population explosion** is generally defined as a rapid and significant increase in population size, typically characterized by an annual growth rate exceeding **2%**. - This rate indicates a **doubling time** of approximately 35 years or less, leading to substantial demographic changes. - In the context of Indian demographics, this definition is particularly relevant to the period of rapid population growth experienced in the mid-20th century. *0.5% - 1.0%* - A growth rate in this range is considered **moderate** or even **low** for many developing countries and would not be indicative of a "population explosion." - This rate represents a relatively **stable** or slowly increasing population, not the rapid surge implied by the term. *1.5% - 2.0%* - While a 1.5% to 2.0% growth rate is significant, it often falls short of the threshold typically associated with a "population explosion," which implies a more **accelerated** and **unsustainable** rate of increase. - Many countries with this growth rate face challenges, but it's generally not classified as an "explosion" unless other contextual factors are extreme. *1.0% - 1.5%* - A growth rate between 1.0% and 1.5% is considered a **moderate** rate of population increase. - This range does not signify the rapid and often unmanageable growth implied by the term **population explosion**.

Question 1773: What is the descending order of cancer incidence among males globally for the following cancer types?

A. Pharynx > lung > oral > esophagus
B. Esophagus > oral > stomach > lung
C. Oral > lung > pharynx > esophagus
D. Lung > oral > pharynx > esophagus (Correct Answer)

Explanation: ***Oral > lung > pharynx > esophagus*** - This sequence accurately reflects the **prevalence rates** of cancers among males [1], with **oral cancer** notably high in certain regions. - **Lung cancer** follows as the second most prevalent due to risk factors like **smoking** and air pollution [1]. *Lung > oral > pharynx > esophagus* - While lung cancer is indeed common, this order is incorrect as it **underestimates oral cancer**, which is highly prevalent in specific populations. - The ranking does not reflect **regional variations** in cancer prevalence, particularly in areas with high oral cancer rates. *Esophagus > oral > stomach > lung* - This order inaccurately places **esophageal cancer** above oral cancer, failing to account for the high prevalence of oral cancers in many regions. - The statement does not align with common epidemiological data that shows **lung cancer preeminence** in general male populations [1]. *Pharynx > lung > oral > esophagus* - This incorrect sequence ranks pharyngeal cancer too high, ignoring the more **established prevalence** of oral and lung cancers. - The order does not reflect the understanding that **lung cancer** remains one of the leading cancers among men [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 284-286.

Question 1774: Randomization is done to reduce?

A. Recall bias
B. Selection bias (Correct Answer)
C. Berksonian bias
D. Reporting bias

Explanation: ***Selection bias*** - **Randomization** ensures that each participant has an equal chance of being assigned to any study group, which helps to distribute both known and unknown confounding factors evenly. - This process minimizes **selection bias** by promoting comparability between groups, making it more likely that any observed differences are due to the intervention rather than pre-existing differences. *Recall bias* - **Recall bias** occurs when there are systematic differences in the way participants remember or report past exposures or events, often seen in retrospective studies. - While randomization helps control for confounding, it does not directly prevent participants from inaccurately recalling information. *Berksonian bias* - **Berksonian bias** is a form of selection bias where the probability of being admitted to a hospital (or selected into a study) is affected by the presence of a co-morbidity, leading to a distorted association between diseases. - Randomization aims to balance characteristics *within* the study groups once participants are recruited, but it doesn't address biases related to the initial selection into the study population from a larger source. *Reporting bias* - **Reporting bias** refers to selective revealing or suppression of information, either by study participants (e.g., social desirability bias) or by researchers (e.g., only reporting positive findings). - Randomization helps ensure internal validity by creating comparable groups, but it does not prevent individuals from selectively reporting outcomes or experiences.

Question 1775: In the context of disease screening, which type of lead time is most beneficial for effective screening?

A. Short lead time
B. Both short and long lead times are beneficial
C. Long lead time is beneficial for screening (Correct Answer)
D. Lead time has no impact on screening effectiveness

Explanation: ***Long lead time is beneficial for screening*** - **Long lead time** provides a greater window of opportunity between disease detection by screening and clinical symptom onset - This extended asymptomatic detectable phase allows for **early intervention** when treatments are most effective - Longer lead time correlates with improved prognosis and potential prevention of severe outcomes - Essential criterion for effective screening programs per **Wilson-Jungner criteria** *Short lead time* - Limited time between disease detectability and clinical symptoms - Reduces screening effectiveness as disease progresses rapidly - Minimal opportunity for beneficial early intervention *Both short and long lead times are beneficial* - Only **long lead time** is beneficial for screening programs - Short lead time actually limits screening effectiveness - Screening benefit is directly proportional to duration of asymptomatic detectable phase *Lead time has no impact on screening effectiveness* - **Lead time is crucial** for determining screening program effectiveness - Directly impacts the window for early detection and intervention - Without adequate lead time, screening loses its preventive value

Question 1776: When is screening for breast cancer recommended?

A. When the disease has a low case fatality rate
B. When diagnostic tools are available
C. When no effective treatment is available
D. When early diagnosis can change the disease course due to effective treatment (Correct Answer)

Explanation: ***When early diagnosis can change the disease course due to effective treatment*** - **Screening** for cancer, like breast cancer, is most beneficial when early detection allows for interventions that effectively alter the disease's natural progression, leading to better outcomes. - The availability of **effective treatments** is a cornerstone for recommending screening programs, as finding a disease early without the means to treat it effectively offers little patient benefit. *When the disease has a low case fatality rate* - Diseases with a **low case fatality rate** are generally less urgent candidates for widespread screening, as the potential benefit of early detection is diminished if the disease is not often fatal. - Screening is more commonly applied to diseases with **significant morbidity and mortality**, where early intervention can make a substantial difference. *When diagnostic tools are available* - While the availability of **diagnostic tools** is a prerequisite for screening, it is not the sole determinant for recommending a screening program. - The diagnostic tools must also be **accurate, safe, and cost-effective**, and their use must lead to improved patient outcomes through early intervention. *When no effective treatment is available* - If **no effective treatment** is available, screening for a disease can cause more harm than good due to the psychological burden of diagnosis without the possibility of intervention. - In such cases, screening is generally not recommended, as it does not improve **patient prognosis** or quality of life.

Question 1777: Which of the following diseases is not covered under the Integrated Disease Surveillance Project (IDSP)?

A. Tuberculosis
B. Cholera
C. Herpes zoster (Correct Answer)
D. Meningococcal disease

Explanation: ***Herpes zoster*** - **Herpes zoster** (shingles) is not included in the Integrated Disease Surveillance Project (IDSP) as it is neither an epidemic-prone disease nor a notifiable disease under the program. - IDSP focuses on diseases with significant public health impact, epidemic potential, or those requiring immediate public health response. - While herpes zoster can cause morbidity in immunocompromised individuals, it does not pose a widespread public health threat requiring national surveillance. *Tuberculosis* - **Tuberculosis (TB)** is explicitly covered under IDSP as a major notifiable disease due to its high burden in India and significant public health importance. - TB surveillance under IDSP helps monitor disease trends, detect outbreaks, and evaluate the effectiveness of the National Tuberculosis Elimination Programme. - Regular reporting and surveillance are essential for achieving TB elimination goals. *Cholera* - **Cholera** is a priority disease under IDSP as an epidemic-prone disease with potential for rapid outbreaks and high mortality if untreated. - It is part of the core surveillance list due to its ability to cause severe dehydration and waterborne epidemics. - Early detection through IDSP enables timely implementation of control measures including safe water supply and oral rehydration therapy. *Meningococcal disease* - **Meningococcal disease** (acute bacterial meningitis) is covered under IDSP due to its high case fatality rate, epidemic potential, and need for urgent public health response. - Surveillance is critical for early outbreak detection and implementation of preventive measures such as mass vaccination and chemoprophylaxis. - Close monitoring helps identify circulating serotypes and guide vaccination strategies.

Question 1778: Which of the following conditions does not primarily benefit from secondary level prevention?

A. Coronary heart disease
B. Leprosy
C. TB
D. None of the options (Correct Answer)

Explanation: ***None of the options*** - This is the **correct answer** because all three conditions listed (Coronary heart disease, TB, and Leprosy) DO significantly benefit from **secondary prevention** strategies. - The question uses negation ("does not"), asking which condition does NOT benefit from secondary prevention. - Since all three diseases benefit from secondary prevention, the answer is "None of the options." **Why each condition DOES benefit from secondary prevention:** *Coronary Heart Disease (CHD)* - **Secondary prevention** includes screening for risk factors (hypertension, hyperlipidemia, diabetes), early detection through ECG and cardiac biomarkers, and prompt intervention. - Post-event management with antiplatelets, statins, beta-blockers, and lifestyle modifications prevents recurrence and reduces mortality. - Early detection and treatment of risk factors halt disease progression and prevent complications. *Tuberculosis (TB)* - **Secondary prevention** is crucial through **early case detection** (contact tracing, active case finding, screening high-risk populations) and **prompt initiation of antitubercular therapy**. - Early diagnosis via sputum microscopy, GeneXpert, and chest X-ray prevents disease progression, reduces transmission, and prevents complications like miliary TB or TB meningitis. - Timely treatment ensures cure and prevents development of drug resistance. *Leprosy* - **Secondary prevention** involves **active case detection through surveys** and **prompt multi-drug therapy (MDT)**. - Early diagnosis and treatment prevent irreversible nerve damage, deformities, and disabilities. - Reduces transmission in the community and prevents progression to advanced stages.

Question 1779: Which of the following is NOT a criterion for defining a polio epidemic?

A. Caused by same virus type
B. Cases should occur in same locality
C. 2 or more cases
D. Cases occurring during a 6 month period (Correct Answer)

Explanation: ***Correct: Cases occurring during a 6 month period*** - The definition of a polio epidemic primarily focuses on criteria like the number of cases, their geographical proximity, and the viral serotype causing the infection, not a specific duration of time over which cases occur. - While an outbreak naturally unfolds over a period, a fixed 6-month window is **not a formal defining criterion** for an epidemic, which typically emphasizes a sudden, significant increase above expected levels. *Incorrect: 2 or more cases* - An epidemic is generally defined by an **unusual increase in disease incidence**, and even two confirmed cases, especially in areas with low endemicity or where polio is eradicated, can signal an outbreak. - The presence of **two or more paralytic polio cases** within a specific area is often considered a critical threshold for declaring an epidemic, particularly for **wild poliovirus**. *Incorrect: Cases should occur in same locality* - For an epidemic to be declared, the cases must be **geographically linked** to indicate a common source or local transmission. - Cases spread across different, unconnected regions would suggest **sporadic occurrences** rather than a localized epidemic. *Incorrect: Caused by same virus type* - An epidemic implies a **common etiologic agent**, meaning the cases should be linked to the same serotype of **poliovirus** (e.g., wild poliovirus type 1). - If cases are caused by different serotypes, it indicates **multiple independent introductions** rather than a single epidemic outbreak.

Question 1780: Which of the following demographic characteristics can be GENERALLY assessed from the visual structure of a population pyramid without requiring precise statistical calculations?

A. Exact male-to-female population ratios
B. Life expectancy (Correct Answer)
C. Immigration and emigration rates
D. Crude birth rate per 1,000 population

Explanation: ***Life expectancy*** - A population pyramid visually represents the age and sex distribution of a population, which allows for a general inference of **life expectancy** based on the pyramid's shape. - A pyramid with a broad base and rapidly tapering top suggests **lower life expectancy**, while one with a more rectangular shape in older age cohorts indicates **higher life expectancy**. *Exact male-to-female population ratios* - While the pyramid shows the proportion of males and females in each age group, determining **exact numerical ratios** for the entire population from a visual glance is difficult. - Precise calculation would require **specific data values** for each bar. *Immigration and emigration rates* - Population pyramids can sometimes show **"bulges" or "indents"** in specific age groups that might hint at past large-scale migration. - However, **direct assessment of rates** (e.g., how many people per 1,000 immigrated or emigrated) from its visual structure alone is not possible. *Crude birth rate per 1,000 population* - The **width of the base** of the pyramid gives a general idea of the birth rate, with a wider base indicating higher births. - However, to determine the **exact crude birth rate per 1,000**, specific statistical data is required, not just a visual assessment of the pyramid's shape.

Practice by Chapter

Principles of Epidemiology

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Measures of Disease Frequency

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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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