Epidemiology — MCQs

Epidemiology Indian Medical PG Practice Questions and MCQs

Question 1601: Which of the following is true about annual risk of TB (ARI)

A. ARI of 1% = 50 new cases
B. It represents new cases of TB
C. Current ARI in India is 1.7%
D. It is assessed by tuberculin conversion in previously non-vaccinated children (Correct Answer)

Explanation: ***It is assessed by tuberculin conversion in previously non-vaccinated children*** - Annual Risk of Infection (ARI) is estimated by measuring the rate of **tuberculin skin test conversion** in populations, particularly in **children who have not been vaccinated** with BCG. - Tuberculin conversion in a child indicates recent exposure and infection with **Mycobacterium tuberculosis**. *ARI of 1% = 50 new cases* - This statement is a **misinterpretation** of ARI; the standard epidemiological conversion is that **1% ARI corresponds to approximately 50 new smear-positive TB cases per 100,000 population per year**. - However, **ARI represents new infections**, not a fixed number of disease cases. The number of **active TB cases** depends on several factors, including progression rate from infection to disease and population characteristics. *It represents new cases of TB* - **ARI represents new infections**, not new cases of active TB disease. Only a proportion of infected individuals (approximately 5-10% lifetime risk) will develop active TB disease. - **TB incidence** refers to new cases of active TB disease, whereas ARI refers to the infection rate in the population. *Current ARI in India is 1.7%* - Recent estimates for ARI in India have shown significant decline due to effective TB control programs, with current ARI estimated at **approximately 0.5-1%** or lower in many regions. - The **actual ARI varies** by region and is influenced by factors like TB control programs, population density, and socioeconomic conditions.

Question 1602: The pattern of change in disease trends where infectious diseases are replaced by degenerative and non-communicable diseases as the main causes of morbidity and mortality is known as:

A. Paradoxical transition
B. Demographic transition
C. Cross transition
D. Epidemiological transition (Correct Answer)

Explanation: ***Epidemiological transition*** - The **epidemiological transition** describes the shift in disease patterns from infectious diseases as leading causes of death to non-communicable, chronic, and degenerative diseases. - This transition is typically associated with **socioeconomic development**, improved public health, sanitation, and increased life expectancy. - It was first described by **Abdel Omran** in 1971 and includes three stages: the age of pestilence and famine, the age of receding pandemics, and the age of degenerative and man-made diseases. *Incorrect: Paradoxical transition* - This term is **not a recognized concept** in epidemiology. - It does not describe a systemic pattern of disease trend changes. *Incorrect: Demographic transition* - The **demographic transition** refers to changes in birth and death rates over time in a population, leading to shifts in age structure. - While related to epidemiological changes, it specifically describes **population dynamics**, not disease patterns themselves. - It typically precedes or accompanies epidemiological transition. *Incorrect: Cross transition* - This term is **not a recognized concept** in epidemiology. - It does not describe a systemic pattern of disease trend changes.

Question 1603: The time interval between reception of infection and maximum infectivity of the host is known as-

A. Median incubation period
B. Generation time
C. Serial interval
D. Latent period (Correct Answer)

Explanation: ***Latent period*** - This is the time from **infection to infectiousness**, meaning the period until the host can transmit the pathogen to another susceptible host. - The highest infectivity typically occurs during this period or shortly after its completion, making it a critical measure for understanding disease transmission. *Median incubation period* - The **incubation period** is the time from exposure to a pathogen until the first appearance of symptoms. - The median incubation period represents the **midpoint** of this time frame across an infected population. *Generation time* - **Generation time** is defined as the interval between the onset of infectiousness in a primary case and the onset of infectiousness in a secondary case infected by the primary case. - It measures the **time between successive generations of infection**, not the time to maximum infectivity within a single host. *Serial interval* - The **serial interval** is the time from symptom onset in a primary case to symptom onset in a secondary case infected by the primary case. - It is a measure related to the **spread of symptomatic illness**, and while often correlated with generation time, it is not specifically about the host's infectivity level.

Question 1604: WER stands for

A. Weekly epidemiological record (Correct Answer)
B. World epidemic record
C. Weekly environmental record
D. World epidemiological record

Explanation: ***Weekly epidemiological record*** - The **Weekly Epidemiological Record (WER)** is a key publication of the **World Health Organization (WHO)**. - It serves as an essential instrument for the rapid dissemination of **epidemiological information** on cases and outbreaks of diseases under the **International Health Regulations**. *World epidemic record* - This option is incorrect because while the WER deals with **epidemics**, the full and correct name emphasizes the **weekly publication schedule** and broader "epidemiological" scope, not just "epidemic." - Using "World epidemic record" is not the accepted or official nomenclature for the publication. *Weekly environmental record* - This option is incorrect as the **WER** focuses specifically on **disease surveillance** and **epidemiology**, not environmental data. - While environmental factors can influence disease, the primary scope of the WER is on disease prevalence, incidence, and outbreaks. *World epidemiological record* - This option is incorrect because the official publication is called the **"Weekly" Epidemiological Record**, highlighting its regular, week-by-week updates. - Omission of "Weekly" changes the accuracy of the title.

Question 1605: Disease highly transmitted during incubation period is -

A. Pertussis
B. Cholera
C. Measles
D. Brucellosis
E. Chickenpox (Correct Answer)

Explanation: ***Chickenpox (Varicella)*** - Chickenpox is **highly contagious during the late incubation period**, specifically **1-2 days before the rash appears**. - The incubation period is 10-21 days (usually 14-16 days), and transmission begins **before any clinical symptoms** are evident. - This makes chickenpox unique as it spreads efficiently during the true incubation period (asymptomatic phase). - Transmission continues until **all lesions have crusted over** (usually 5-7 days after rash onset). *Measles* - While measles is highly contagious, it is most infectious during the **prodromal phase** (fever, cough, coryza, conjunctivitis) and early rash phase. - The prodromal phase occurs **after the incubation period ends** (incubation is 10-14 days of asymptomatic infection). - Some transmission may occur in the last 1-2 days of incubation, but peak infectivity is during the symptomatic prodromal phase. *Pertussis* - Pertussis is most contagious during the **catarrhal stage**, which follows the incubation period. - The catarrhal stage is characterized by runny nose, low-grade fever, and mild cough (symptomatic phase). - Infectivity decreases significantly after 3 weeks of illness or after 5 days of appropriate antibiotic therapy. *Cholera* - Cholera is transmitted via the **fecal-oral route** through contaminated water or food. - While some bacterial shedding occurs during incubation, peak transmission happens during the **symptomatic phase** with severe diarrhea causing massive bacterial shedding. - Most transmission occurs from symptomatic or recently symptomatic individuals.

Question 1606: Population of a village on 1st January is 16,500. Since 1st January, 22 new cases of TB were detected during the year. Total registered cases were 220. What is the incidence of TB?

A. 100 per 100,000
B. 133 per 100,000 (Correct Answer)
C. 121 per 100,000
D. 111 per 100,000

Explanation: ***133 per 100,000*** - The **incidence rate** calculates the frequency of new occurrences of a disease in a population over a specified time period. - It is calculated as (Number of new cases / Population at risk) * 100,000. Here, (22 / 16,500) * 100,000 = **133.33 per 100,000**. *100 per 100,000* - This value would be obtained if the number of new cases was 16.5 (16.5 / 16,500 * 100,000). - This calculation does not reflect the given number of **new cases (22)**. *121 per 100,000* - This value would be obtained if the number of new cases was 20 (20 / 16,500 * 100,000) or if the **population was different**. - This option does not match the actual data provided for the new cases and population. *111 per 100,000* - This value would be obtained if the number of new cases was approximately 18.3 (18.3 / 16,500 * 100,000). - It does not correctly reflect the **incidence calculation** based on the given number of 22 new cases.

Question 1607: "Tracking" of blood pressure means:

A. Controlling high BP with nifedipine
B. High blood pressures in children tend to perpetuate in adults (Correct Answer)
C. Pictorial representation of serial blood pressures of an individual
D. None of the options

Explanation: ***High blood pressures in children tend to perpetuate in adults*** - **Blood pressure tracking** refers to the phenomenon where an individual's blood pressure percentile rank in childhood tends to be maintained into adulthood. - This means that children with higher blood pressure readings are more likely to have higher blood pressure as adults, increasing their risk for **hypertension** and cardiovascular disease. - This is the **correct definition** of blood pressure tracking in epidemiology. *Controlling high BP with nifedipine* - This describes a **pharmacological intervention** for hypertension, specifically using a calcium channel blocker like nifedipine. - It does not relate to the concept of **blood pressure "tracking,"** which is an epidemiological observation of blood pressure trends over time, not a treatment method. *Pictorial representation of serial blood pressures of an individual* - This describes **blood pressure monitoring** or charting, which is a method of recording and visualizing blood pressure data over time. - While helpful for managing individual blood pressure, it is not the definition of **blood pressure "tracking,"** which refers to the long-term persistence of blood pressure percentile levels from childhood into adulthood. *None of the options* - This option is incorrect because **"High blood pressures in children tend to perpetuate in adults"** accurately defines the concept of blood pressure tracking.

Question 1608: In the International death certificate one of the following is not true -

A. Part I of the certificate deals with the immediate cause and also the underlying cause
B. Part I of the certificate deals with the immediate cause only (Correct Answer)
C. Part II records significantly associated diseases
D. The certificate has been recommended by the WHO for international comparability

Explanation: ***Part I of the certificate deals with the immediate cause only*** - This statement is **incorrect** and is the answer to this "NOT true" question. Part I of the International Death Certificate is designed to capture the **sequence of events leading directly to death**, not just the immediate cause. - It specifically records the **immediate cause of death** (line a), followed by **antecedent conditions** (intermediate causes on lines b and c), and finally the **underlying cause of death** (the disease or injury that initiated the chain of events). - The underlying cause is the most important for mortality statistics and public health surveillance. *Part I of the certificate deals with the immediate cause and also the underlying cause* - This statement is **true**. Part I is structured to record both the **immediate cause** and the **underlying cause**, along with any intervening conditions in the causal chain. - The format typically has lines a, b, c, and d, where line a is the immediate cause and the lowest used line represents the underlying cause. *The certificate has been recommended by the WHO for international comparability* - This statement is **true**. The **International Death Certificate** (also called the Medical Certificate of Cause of Death) has been recommended by the **WHO** for standardizing death certification globally. - Its purpose is to ensure **international comparability of mortality statistics**, enabling consistent data collection for epidemiological surveillance, public health planning, and research across countries. *Part II records significantly associated diseases* - This statement is **true**. Part II of the International Death Certificate records other **significant conditions** that contributed to death but were **not part of the direct causal sequence** recorded in Part I. - These are conditions that may have **influenced the outcome** or were important to the overall clinical picture but did not directly cause death.

Question 1609: What happens in disease elimination:

A. Interruption of disease transmission from large geographical areas (Correct Answer)
B. Global eradication of disease agent
C. Incidence is reduced by 10%
D. Prevalence is reduced by 10%

Explanation: ***Interruption of disease transmission from large geographical areas*** - **Disease elimination** refers to the sustained absence of **disease transmission** in a defined geographical area, even though the causative agent may still exist elsewhere. - This typically involves **successful implementation of control measures** that prevent new cases from arising within that region. *Global eradication of disease agent* - **Eradication** signifies the **permanent reduction to zero of the worldwide incidence** of infection caused by a specific agent. - This is a more ambitious goal than elimination, requiring the destruction of all reservoirs of the pathogen. *Incidence is reduced by 10%* - A **10% reduction in incidence** is a measure of **disease control**, indicating a decrease in the rate of new cases. - While a positive outcome, it does not necessarily imply the interruption of disease transmission or elimination. *Prevalence is reduced by 10%* - A **10% reduction in prevalence** indicates that the **total number of existing cases** in the population has decreased. - Similar to incidence reduction, this is a measure of **disease control** but does not equate to the absence of transmission or elimination of the disease.

Question 1610: An influenza pandemic is defined as:

A. A worldwide epidemic of influenza caused by a new virus strain (Correct Answer)
B. A localized outbreak of seasonal influenza
C. An annual recurrence of influenza in winter months
D. A gradual increase in influenza cases over several years

Explanation: ***A worldwide epidemic of influenza caused by a new virus strain*** - An influenza pandemic is defined as the **global spread of a novel influenza virus** to which the human population has **little or no immunity**. - According to WHO, a pandemic occurs when a new influenza virus emerges that is capable of **sustained human-to-human transmission** across **multiple countries and continents**. - The key defining features are: **worldwide geographic spread**, **novel virus strain**, and **lack of population immunity** leading to widespread illness. *A gradual increase in influenza cases over several years* - This is **incorrect** - pandemics can develop **rapidly**, not necessarily gradually over years. - Examples: the 2009 H1N1 pandemic spread globally within **weeks to months**, not years. - A gradual increase could describe endemic disease patterns, not the sudden emergence characteristic of pandemics. *A localized outbreak of seasonal influenza* - This describes a **local epidemic or outbreak**, not a pandemic. - The term "localized" is the opposite of pandemic, which requires **widespread geographic distribution**. - **Seasonal influenza** involves circulating strains with existing population immunity, unlike pandemic strains. *An annual recurrence of influenza in winter months* - This describes **seasonal/endemic influenza**, which occurs predictably with established viral strains. - Pandemics involve **novel strains** causing unexpected, widespread disease, not predictable annual patterns. - Seasonal flu is limited in severity due to existing immunity from prior exposure or vaccination.

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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