Epidemiology Practice Questions

Q: Under IDSP, which diseases are included under sentinel surveillance?

HIV + HBV. ***HIV + HBV***- **Sentinel surveillance** under IDSP is utilized for diseases where continuous monitoring of specific, defined sites (sentinel sites) provides crucial incidence or prevalence trends, such as **HIV** and **Hepatitis B Virus (HBV)**.- This method is essential for monitoring these diseases as it provides reliable data on prevalence and long-term trends, often focusing on high-risk or specific population groups.*HIV + TB*- While **HIV** is included in sentinel surveillance, **Tuberculosis (TB)** is primarily monitored through **passive surveillance** using mandatory case notification to track incidence and treatment outcomes.- TB is a reportable disease utilizing a robust notification system (e.g., Nikshay portal in India), which differs from the specialized, site-specific sampling used for sentinel surveillance.*Malaria + Dengue*- **Malaria** and **Dengue** are typically included in **syndromic and presumptive surveillance** streams under IDSP due to their potential for rapid outbreaks and the need for immediate, widespread reporting.- Monitoring for these vector-borne diseases focuses on early detection of outbreaks involving fever in defined geographical areas, rather than long-term prevalence trends at specialized sentinel sites.*Measles + Diphtheria*- These diseases are **vaccine-preventable diseases** and are monitored using **enhanced surveillance** protocols to achieve elimination/eradication targets.- Enhanced surveillance requires immediate investigation and reporting of every suspected case to track coverage gaps and initiate immediate public health measures, differing from the sentinel approach.

Q: In a class of 100 students, 80% students were immunised with measles, 12 were affected. What is the primary attack rate?

60%. ***60%*** - The **Primary Attack Rate** measures the number of new cases among the susceptible population during an outbreak; the susceptible population must first be determined by excluding the immunized students. - Calculation: The total susceptible population is 100 students - 80 immunized students = **20 susceptible contacts**. Primary Attack Rate = (12 affected / 20 susceptible) × 100 = **60%**. *80%* - This figure represents the percentage of students in the class who were **immunised** (80 out of 100), not the attack rate among the susceptible population. - Using 80 as the denominator would incorrectly calculate the rate among the protected group (12/80 = 15%). *70%* - This option is mathematically incorrect and does not result from the standard calculation of **Primary Attack Rate** using the given data (12 cases among 20 susceptible individuals). - It is likely derived from an incorrect calculation or failure to correctly identify the **susceptible population** for the denominator. *50%* - This value is incorrect, as the observed number of affected students (12) leads to a higher rate than 50% when calculated against the susceptible population (20). - A **Primary Attack Rate** of 50% would only account for 10 affected students (50% of 20 susceptible individuals).

Q: A study was conducted in 3 communities (across 3 states) to measure the mean blood pressure in each community. Health workers were assigned to visit each house in the 3 communities. The mean blood pressure of each community was then compared. What is the study design called?

Cross-sectional. ***Cross-sectional***- This design takes a **snapshot** of the population (the 3 communities) at a specific time, simultaneously assessing the current status of the outcome (mean **blood pressure**) in each house.- The goal is to determine the **prevalence** of a characteristic (mean blood pressure) within the defined population by studying individuals (each house) within them.*Case-control*- This design requires comparing individuals who have the outcome (**cases**) to those who do not (**controls**) by looking **retrospectively** for past exposure differences.- The current study does not involve selecting groups based on outcome status (e.g., high BP vs. normal BP) to investigate an antecedent exposure.*Cohort*- A **cohort** study follows groups based on their **exposure status** over a period of time to calculate the **incidence** (rate of new cases) of a specific outcome.- This study measures current blood pressure status in a single visit; it does not track individuals longitudinally to see who develops hypertension later.*Ecological study*- This type of study correlates aggregate data (mean outcomes) across different population groups (e.g., states or countries), where the units of analysis are **populations**, not individuals.- Although the final comparison involves community means (ecological data), the design phase involving detailed collection of individual BP data by visiting **each house** is characteristic of a primary **cross-sectional** survey.

Q: In the context of a new onset of a morbid disease, how does the change in incidence affect the prevalence of the disease?

Incidence and prevalence will increase. ***Incidence and prevalence will increase*** - **Incidence** is the rate of new cases arising in a population; a "new onset" inherently implies that the occurrence of **new cases** is rising or starting. - Since **prevalence** is the total number of existing cases (P ≈ I × D, where D is duration), a rise in new cases (**incidence**) directly contributes to and increases the total existing burden of the disease. *Prevalence is not related to incidence* - This is incorrect because **incidence** (the inflow of new cases) is the primary determinant, along with duration and mortality/cure, of the overall total number of existing cases (**prevalence**). - Prevalence is mathematically linked to incidence; if incidence rises, prevalence typically rises, and if incidence approaches zero, prevalence will eventually fall (assuming cases are cleared). *Incidence will increase, and prevalence will decrease* - When **incidence** increases (more new cases), it leads to an increased rate of accumulation of cases, which consequently increases **prevalence**. - Prevalence only decreases despite increasing incidence if the removal rate (due to death or cure) drastically exceeds the rate of new cases, which is highly unlikely in a scenario described as a "new onset" morbid disease. *Prevalence will increase with a decrease in the incidence* - A decrease in **incidence** (fewer new cases) leads to a decrease in **prevalence** over time, assuming the duration of the disease remains stable. - Prevalence can increase with decreasing incidence only if the **duration** of the disease or survival time increases significantly (e.g., effective palliative treatment without cure), trapping existing cases in the prevalent pool.

Q: Which of the following is true regarding the single exposure point source epidemic?

Explosive in nature. ***Correct: Explosive in nature*** - A **single exposure point source epidemic** involves simultaneous exposure of individuals to a common source over a brief timeframe. - This synchronous exposure results in a rapid, steep rise in the number of cases, giving the outbreak an **explosive onset**. *Incorrect: Has more than one incubation period* - Cases usually cluster within one **incubation period** following the single exposure event, as all infections result from the same limited exposure opportunity. - Having cases spread over multiple incubation periods suggests either a **propagated epidemic** or a sustained common source exposure. *Incorrect: Has multiple peaks* - The defining feature of a point source epidemic is a single, sharp peak corresponding to the time when most exposed individuals develop symptoms within the incubation window. - **Multiple peaks** are characteristic of a **propagated epidemic** where secondary and tertiary cases lead to subsequent waves of infection. *Incorrect: Slow rise and fall* - The graph of a single point source epidemic shows a **rapid rise and fall** because the exposure is terminated quickly and all cases appear almost simultaneously. - A **slow rise and fall** is typical of prolonged exposure (continuous common source) or serial transmission (**propagated epidemics**).

Q: Hand washing during COVID-19 is what level of prevention?

Primary prevention. ***Primary prevention***- Hand washing is a crucial public health measure that provides **specific protection** by removing SARS-CoV-2 from the skin surface, thereby preventing the entry and establishment of the disease.- This level of prevention focuses on actions taken *before* the onset of disease to reduce the incidence of infection, aligning with efforts like **vaccination** and health education.*Primordial prevention*- This is the earliest stage, aimed at preventing the emergence and establishment of **environmental or social conditions** that may lead to the development of risk factors (e.g., discouraging unhealthy lifestyle trends globally).- It addresses pre-existing **underlying determinants** of health, whereas hand washing directly targets an infectious agent.*Secondary prevention*- This level involves actions aimed at early diagnosis and prompt treatment of an existing condition to halt progression (e.g., large-scale **testing/screening** of asymptomatic cases for COVID-19).- Actions taken at this stage occur *after* the infection has begun but before significant symptoms or complications arise.*Tertiary prevention*- This level focuses on measures taken when the disease has already fully developed, aiming to reduce the severity of **complications**, limit disability, and provide **rehabilitation** (e.g., physical therapy for post-COVID syndrome).- It deals with the management and recuperation phase of established illness, which is not applicable to preventive hygiene practices.

Q: A government plans to outline tobacco control laws. What is the level of prevention here?

Primordial prevention. ***Primordial prevention*** - Tobacco control laws represent **primordial prevention** as they are **policy-level interventions** aimed at preventing the emergence of risk factors in the population - This involves creating conditions that minimize hazards to health through **legislative and regulatory measures** - By outlining tobacco control laws, the government prevents the establishment of patterns of tobacco use at the **population level** before individual exposure occurs *Primary prevention* - Refers to interventions targeting individuals who are at risk but haven't developed disease (e.g., smoking cessation programs, health education campaigns) - Operates at the **individual level** rather than policy level *Secondary prevention* - Involves early detection and treatment of disease in asymptomatic individuals (e.g., screening programs) - Not applicable to legislative measures *Tertiary prevention* - Focuses on reducing complications and disability in those already diagnosed with disease (e.g., rehabilitation programs) - Not related to policy formulation

Q: Highest birth rate is seen in which stage of the demographic cycle?

Stage I. ***Stage I***- This stage, also known as the **High Stationary** phase, is characterized by a **high birth rate** and a high death rate.- The high birth rate is maintained due to factors like **traditional societal norms**, lack of family planning, and high infant mortality necessitating more children for survival.*Stage II*- In this stage (**Early Expanding**), the **death rate begins to fall sharply** due to improvements in sanitation, nutrition, and healthcare.- While the birth rate remains high, leading to the maximum population growth, it is typically equivalent to or slightly lower than the birth rate seen in Stage I.*Stage III*- This stage (**Late Expanding**) is defined by a **sharp decrease** in the **birth rate** due to urbanization, increased education, and adoption of family planning measures.- Both the birth rate and death rate are falling, meaning the birth rate is significantly lower than that observed in Stage I.*Stage IV*- This stage (**Low Stationary**) is characterized by both a **low birth rate** and a **low death rate**, resulting in very slow or zero population growth.- This stage reflects fully developed countries where fertility rates are close to or below the replacement level.

Q: What is the denominator in infant mortality rate?

1000. ***Correct: 1000*** - The **Infant Mortality Rate (IMR)** is standardly calculated as the number of deaths of infants under one year of age per **1000 live births** in a given population and time period - This denominator (per **1000 live births**) is the international standard adopted by organizations like the **WHO** for standardized calculation and comparison of vital rates - IMR is expressed as deaths per 1000 live births, making it directly comparable across different populations and time periods *Incorrect: 100* - A denominator of **100** is used when expressing a rate as a **percentage**, which is not the conventional methodology for reporting IMR - Using 100 as the denominator would convert the IMR into a percentage, which is not conducive to reliable international comparisons - Standard vital statistics use 1000 as the base denominator *Incorrect: 10,000* - A denominator of **10,000** is occasionally used for reporting rates of very specific, **less common** public health events or diseases - It is **not** the traditional choice for IMR; standard indices of mortality (like Crude Death Rate, Birth Rate, IMR) rely on a base of **1000** *Incorrect: 1,00,000* - A denominator of **1,00,000** (one lakh) is primarily used when calculating incidence or prevalence of extremely **rare diseases** or specific morbidity rates in large populations - While it provides larger whole numbers, it violates the conventional rule that major vital statistics rates (like IMR) use **1000** as the denominator

Question 1

Under IDSP, which diseases are included under sentinel surveillance?

Accepted Answer

HIV + HBV

Answer

Measles + Diphtheria

Answer

Malaria + Dengue

Answer

HIV + TB

Question 2

In a class of 100 students, 80% students were immunised with measles, 12 were affected. What is the primary attack rate?

Accepted Answer

60%

Answer

80%

Answer

70%

Answer

50%

Question 3

A study was conducted in 3 communities (across 3 states) to measure the mean blood pressure in each community. Health workers were assigned to visit each house in the 3 communities. The mean blood pressure of each community was then compared. What is the study design called?

Accepted Answer

Cross-sectional

Answer

Case-control

Answer

Ecological study

Answer

Cohort

Question 4

A gym owner observes that individuals who drink iced tea during their workouts tend to lose more weight. What is the nature of this relationship?

Accepted Answer

Indirect

Answer

Direct

Answer

Spurious

Answer

Relative

Question 5

In the context of a new onset of a morbid disease, how does the change in incidence affect the prevalence of the disease?

Accepted Answer

Incidence and prevalence will increase

Answer

Prevalence is not related to incidence

Answer

Incidence will increase, and prevalence will decrease

Answer

Prevalence will increase with a decrease in the incidence

Question 6

Which of the following is true regarding the single exposure point source epidemic?

Accepted Answer

Explosive in nature

Answer

Has more than one incubation period

Answer

Has multiple peaks

Answer

Slow rise and fall

Question 7

Hand washing during COVID-19 is what level of prevention?

Accepted Answer

Primary prevention

Answer

Secondary prevention

Answer

Tertiary prevention

Answer

Primordial prevention

Question 8

A government plans to outline tobacco control laws. What is the level of prevention here?

Accepted Answer

Primordial prevention

Answer

Secondary prevention

Answer

Tertiary prevention

Answer

Primary prevention

Question 9

Highest birth rate is seen in which stage of the demographic cycle?

Accepted Answer

Stage I

Answer

Stage II

Answer

Stage III

Answer

Stage IV

Question 10

What is the denominator in infant mortality rate?

Accepted Answer

1000

Answer

100

Answer

10,000

Answer

1,00,000

Epidemiology — MCQs

Epidemiology — MCQs

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