Epidemiology — MCQs
On this page
Leprosy is considered a public health problem if the prevalence of leprosy is more than:
Crude mortality rate is expressed as
What do migration studies primarily focus on regarding health outcomes?
What is the definition of sex ratio?
Which type of epidemiological study uses a population as the unit of study?
What is the simplest and most commonly used measure of mortality?
What is the most common cause of death in children aged 1-4 years in India?
Among the following diseases where chemoprophylaxis is considered for epidemiological control, it is least practical for:
What is the definition of disease rate?
Cheopis index is used for
Epidemiology Indian Medical PG Practice Questions and MCQs
Question 1851: Leprosy is considered a public health problem if the prevalence of leprosy is more than:
- A. 2 per 10,000
- B. 1 per 10,000 (Correct Answer)
- C. 5 per 10,000
- D. 10 per 10,000
Explanation: ***1 per 10,000*** - The World Health Organization (WHO) defines leprosy as a public health problem if its prevalence is one or more cases per **10,000 population**. - This threshold guides global and national strategies for **leprosy elimination** and control efforts. *2 per 10,000* - While this is a concerning prevalence rate, the internationally accepted threshold for defining leprosy as a public health problem is lower, at **1 per 10,000**. - A rate of 2 per 10,000 would already indicate a significant public health burden, meeting and exceeding the WHO criterion. *5 per 10,000* - This prevalence rate is significantly higher than the WHO's established threshold, indicating an advanced stage of leprosy as a public health problem. - Countries reaching this level of prevalence would require **intensive control measures** and urgent intervention. *10 per 10,000* - A prevalence of 10 per 10,000 signifies a very severe public health crisis regarding leprosy, far exceeding the definition of a public health problem. - At this rate, the disease would be **highly endemic**, requiring immediate and comprehensive public health responses.
Question 1852: Crude mortality rate is expressed as
- A. Per 1000 individuals (Correct Answer)
- B. Per 100 individuals
- C. Per 10,000 individuals
- D. Per 100,000 individuals
Explanation: ***Per 1000 individuals*** - The **crude mortality rate** is typically expressed as the number of deaths per 1000 people in a given population over a specified period. - This standard allows for easier comparison of mortality burdens across different populations and enables health authorities to track overall health trends. *Per 100 individuals* - While rates can theoretically be expressed per 100, a **crude mortality rate** is almost universally standardized to 1000 individuals to obtain more manageable and interpretable numbers, especially in larger populations. - Expressing it per 100 might result in very small decimal values, which are less convenient for general reporting. *Per 10,000 individuals* - Rates per **10,000 individuals** are sometimes used for less common events or specific statistical analyses, but not for the standard definition of crude mortality. - The standard denominator for **crude mortality** is 1,000, making it easier to compare with other common epidemiological rates. *Per 100,000 individuals* - Rates per **100,000 individuals** are typically reserved for very rare diseases or specific epidemiological measures like **maternal mortality rates** or **cancer incidence rates**, where the absolute numbers might be too small to be meaningful when expressed per 1,000. - The **crude mortality rate** is a broad measure of population health and uses a smaller denominator for general comparability.
Question 1853: What do migration studies primarily focus on regarding health outcomes?
- A. None of the options
- B. Distinguishing genetic from environmental factors in disease causation (Correct Answer)
- C. Genetic influences on disease prevalence
- D. Socioeconomic factors affecting health outcomes
Explanation: ***Distinguishing genetic from environmental factors in disease causation*** - Migration studies are a **classic epidemiological tool** used to determine whether diseases are primarily due to **genetic/ethnic factors** or **environmental/lifestyle factors** - By comparing disease rates in migrants with rates in their **country of origin** and **host country**, researchers can identify which factors drive disease patterns - **Key principle**: If migrants adopt the disease pattern of the host country, this suggests **environmental causation**; if they retain the pattern of their origin country, this suggests **genetic/ethnic factors** - **Classic examples**: Japanese migrants to Hawaii showing increased CHD rates (environmental), changes in cancer patterns among migrants indicating dietary influences *Health distribution patterns among populations* - While migration studies do examine distribution patterns, this is too **generic and vague** to describe their primary purpose - All epidemiological studies examine health distribution - this doesn't capture what makes migration studies **unique and valuable** - The specific value of migration studies lies in their ability to **disentangle genetic from environmental causation**, not just describe distributions *Genetic influences on disease prevalence* - This is partially correct but **incomplete** - migration studies don't just study genetic influences in isolation - They specifically examine genetic influences **in comparison to environmental factors** to determine relative contributions - The key is the **comparative framework** that allows distinction between these factor types *Socioeconomic factors affecting health outcomes* - Socioeconomic factors are **one component** of the environmental factors examined in migration studies - However, the primary methodological focus is on **distinguishing causation types** (genetic vs environmental), not just studying socioeconomic factors - Socioeconomic studies can be conducted without migration contexts
Question 1854: What is the definition of sex ratio?
- A. Number of live births per year
- B. Number of females per 1000 males
- C. Number of males per 1000 females (Correct Answer)
- D. Crude birth rate
Explanation: **Number of males per 1000 females** ✓ - The **sex ratio** is a demographic measure that expresses the number of males relative to the number of females in a population, typically presented as the number of males per 1000 females. - This ratio provides insight into the **gender distribution** within a population and can vary significantly due to factors like birth rates, mortality rates, and migration. - This is the **standard definition** used in Census data, WHO reports, and epidemiological studies. *Number of live births per year* - This definition refers to the **absolute number of births** occurring within a specific time frame, typically a year. - It is a component of the **birth rate** but not the definition of sex ratio, which specifically compares the numbers of each sex. *Number of females per 1000 males* - While this is a **ratio of sexes**, it is the inverse of the commonly accepted definition of the sex ratio. - The standard convention is to express the number of males per 1000 females, making this an **unconventional expression** of the sex ratio. *Crude birth rate* - The **crude birth rate** is defined as the number of live births per 1,000 people (of both sexes) in a population per year. - This measure reflects the **overall fertility** of a population and does not distinguish between male and female numbers, unlike the sex ratio.
Question 1855: Which type of epidemiological study uses a population as the unit of study?
- A. Ecological study (Correct Answer)
- B. Cohort study
- C. Experimental study
- D. Case-control study
Explanation: ***Correct - Ecological study*** - An **ecological study** examines exposure-outcome relationships by using **data aggregated at the population level**, rather than individual data. - The unit of analysis is a group (e.g., countries, regions, schools), making it ideal for studying population-level trends and associations. *Incorrect - Cohort study* - A **cohort study** follows a group of individuals (the cohort) over time to determine the incidence of a disease or outcome based on their **exposure status**. - The unit of study is the **individual**, observed prospectively or retrospectively. *Incorrect - Case-control study* - A **case-control study** compares individuals with a disease (cases) to individuals without the disease (controls) to identify past **exposures associated with the disease**. - The unit of study is the **individual**, and it is retrospective in nature. *Incorrect - Experimental study* - An **experimental study** (e.g., a randomized controlled trial) involves an **intervention** applied to a group of individuals and compares outcomes with a control group. - The unit of study is typically the **individual** or a small group, with researchers controlling exposure.
Question 1856: What is the simplest and most commonly used measure of mortality?
- A. Crude death rate (Correct Answer)
- B. Case fatality rate
- C. Specific death rate
- D. Proportional mortality rate
Explanation: ***Crude death rate*** - This is the simplest and most commonly used measure because it reflects the **total number of deaths** in a population over a specified period, relative to the mid-period population. - Its calculation requires only the total number of deaths and the total population size, making it easily accessible and widely applicable for **general mortality comparisons**. *Case fatality rate* - This measures the **proportion of individuals diagnosed with a specific disease** who die from that disease, rather than overall mortality in a population. - It is often used to assess the **severity of a disease** and is not a general measure of mortality. *Proportional mortality rate* - This indicates the **proportion of all deaths due to a specific cause** or age group, rather than the overall death rate in the population. - It does not represent the absolute risk of dying and is influenced by the prevalence of other causes of death. *Specific death rate* - This measure calculates the death rate for a **particular subgroup** (e.g., age-specific, cause-specific, or sex-specific), making it more detailed but not the simplest or most commonly used overall measure. - While more precise for specific analyses, it requires more granular data than the crude death rate.
Question 1857: What is the most common cause of death in children aged 1-4 years in India?
- A. Infections (Correct Answer)
- B. Homicide
- C. Congenital anomalies
- D. Accidents/Unintentional injuries
Explanation: ***Infections*** - **Infections**, particularly pneumonia, diarrheal diseases, and other communicable diseases, are the leading cause of death among children aged 1-4 years in India. - According to WHO and national health data, respiratory infections (especially pneumonia) and diarrheal diseases account for the majority of deaths in this age group. - This pattern is characteristic of developing countries where infectious diseases remain a major public health challenge despite improvements in vaccination coverage. *Accidents/Unintentional injuries* - While **unintentional injuries** (drowning, road traffic accidents, burns, falls) are a significant cause of mortality in children aged 1-4 years, they rank lower than infectious diseases in India. - Accidents are the leading cause in developed countries but not in the Indian context. *Homicide* - **Homicide** is not among the leading causes of death in children aged 1-4 years in India. - While child abuse and violence are serious concerns, they account for a much smaller proportion of deaths compared to infections and injuries. *Congenital anomalies* - **Congenital anomalies** are a major cause of mortality in infants (under 1 year), particularly in the neonatal period. - Their contribution to mortality decreases significantly in the 1-4 years age group as most severe anomalies incompatible with life result in early infant death.
Question 1858: Among the following diseases where chemoprophylaxis is considered for epidemiological control, it is least practical for:
- A. Measles
- B. Cholera
- C. Diphtheria
- D. Tuberculosis (Correct Answer)
Explanation: ***Tuberculosis*** - **Chemoprophylaxis exists** for TB (isoniazid, rifampin regimens) but is the **least practical** for population-level epidemiological control due to **prolonged treatment duration** (6-9 months). - Results in **poor adherence**, high dropout rates, and significant risk of **drug resistance** when implemented as mass chemoprophylaxis, making it impractical for large-scale control. *Measles* - Has **no antimicrobial chemoprophylaxis** available - measles is a **viral infection** with no effective prophylactic antibiotics. - Post-exposure **immune globulin** is passive immunization, not chemoprophylaxis, making this option **not applicable** rather than "least practical." *Cholera* - **WHO does not recommend** antibiotic chemoprophylaxis for cholera control due to **ineffectiveness** and **antibiotic resistance** concerns. - Since chemoprophylaxis is **contraindicated** rather than impractical, this option is **not applicable** to the question of practicality. *Diphtheria* - **Chemoprophylaxis is highly practical** with **erythromycin or penicillin** for close contacts over **short duration** (7-10 days). - Demonstrates **good compliance** and effectiveness in **outbreak control**, making it the most practical chemoprophylaxis option among those that actually use it.
Question 1859: What is the definition of disease rate?
- A. Often expressed as a ratio or percentage
- B. Duration of disease occurrence in a specific timeframe
- C. Likelihood of developing a disease
- D. Frequency of disease occurrence in a population per unit of time (Correct Answer)
Explanation: ***Frequency of disease occurrence in a population per unit of time*** - A disease rate quantifies the **frequency** or **speed** at which disease events (new cases or existing cases) occur within a defined population over a specific time period. - It is a **measure of disease occurrence** that includes three essential components: the number of disease events (numerator), the population at risk (denominator), and a specified time period. - Examples include **incidence rate** (new cases per population per time) and **prevalence rate** (existing cases per population at a point in time). - Rates allow comparison of disease frequency across different populations and time periods. *Often expressed as a ratio or percentage* - While this is **technically correct** (rates are indeed ratios with numerator and denominator), this statement describes the **format** of presentation rather than the fundamental epidemiological concept. - This option focuses on **how** a rate is expressed, not **what** it measures or represents. *Duration of disease occurrence in a specific timeframe* - This refers to the **length of time** a disease persists, not the frequency of its occurrence. - **Duration** relates to concepts like disease course or chronicity, whereas a **rate** measures how often disease events happen. *Likelihood of developing a disease* - This defines **risk** or **probability**, which is related but distinct from a rate. - Risk represents the probability that an individual will develop disease over a specified period, while a rate measures the **speed or frequency** of disease occurrence in a population.
Question 1860: Cheopis index is used for
- A. Plague (Correct Answer)
- B. Infectious mononucleosis
- C. Dengue fever
- D. Typhus fever
Explanation: ***Plague*** - The **Cheopis index** is used to measure the **average number of Xenopsylla cheopis (oriental rat fleas)** per rat. - This index is crucial in determining the risk of **epizootic and epidemic plague**, as fleas are the primary vectors of the bacteria *Yersinia pestis*. *Infectious mononucleosis* - This viral infection, caused by the **Epstein-Barr virus**, is primarily transmitted through **saliva** and not through insect vectors. - Diagnosis involves blood tests for **heterophile antibodies** and atypical lymphocytes, not an entomological index. *Dengue fever* - Dengue is a **mosquito-borne viral illness**, primarily transmitted by **Aedes aegypti** and **Aedes albopictus** mosquitoes. - Its epidemiological surveillance focuses on mosquito indices like the **Breteau index** or **House index**, not the Cheopis index. *Typhus fever* - **Epidemic typhus** is caused by *Rickettsia prowazekii* and transmitted by the **human body louse** (*Pediculus humanus corporis*). - While other forms of typhus (e.g., murine typhus) involve fleas, the Cheopis index is specifically associated with **plague surveillance** in relation to rat fleas.
Practice by Chapter
Principles of Epidemiology
Practice Questions
Measures of Disease Frequency
Practice Questions
Epidemiological Study Designs
Practice Questions
Descriptive Epidemiology
Practice Questions
Analytical Epidemiology
Practice Questions
Experimental Epidemiology
Practice Questions
Screening for Disease
Practice Questions
Surveillance Systems
Practice Questions
Investigation of an Epidemic
Practice Questions
Association and Causation
Practice Questions
Modern Epidemiological Methods
Practice Questions
Critical Appraisal of Epidemiological Studies
Practice Questions
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free