Epidemiology Practice Questions

Q: A person's father had colon cancer. He had bloody stool. So, he just came for a check-up. Before he had not undergone any screening. He was recommended to do a colonoscopy for screening. Screening is which level of prevention?

Secondary. ***Secondary***- **Secondary prevention** involves measures like **screening** and early diagnosis to detect disease (e.g., **colorectal cancer**) in its earliest stages, allowing for timely intervention and reducing the burden of the disease. - A screening colonoscopy fits this definition perfectly, as it aims to identify **precancerous polyps** or early-stage asymptomatic cancer in an at-risk individual who has not yet been formally diagnosed. *Primordial*- **Primordial prevention** targets the underlying determinants of health and aims to prevent the establishment of risk factors themselves in the population (e.g., strict regulations on advertising unhealthy foods). - It operates at a societal level, preceding primary prevention, and is not applicable to an individual undergoing a specific medical screening test. *Primary*- **Primary prevention** aims to prevent disease onset by reducing risk factors or increasing protection *before* the disease process begins (e.g., **vaccination**, lifestyle modification, chemoprophylaxis). - Since this patient is already at high risk (family history) and presenting with an alarming symptom (**bloody stool**), the action is beyond preventing the initial exposure or onset. *Tertiary*- **Tertiary prevention** focuses on managing existing, established disease to prevent complications, reduce disability, and improve the quality of life (e.g., rehabilitation after a stroke, palliative care, or chemotherapy after a cancer diagnosis). - Screening is about early detection, whereas tertiary prevention is focused on minimizing the long-term impact of a disease that is already clinically apparent or diagnosed.

Q: A total of 60 patients were diagnosed with COVID-19. Out of which, 12 deaths were reported. Calculate the Case Fatality Rate?

20%. ***20%*** - The **Case Fatality Rate (CFR)** is calculated by dividing the number of deaths from a specific disease by the total number of confirmed cases of that disease, multiplied by **100** to get the percentage. - Based on the data: (12 deaths / 60 cases) * 100 = **0.20** * 100 = **20%**. *30%* - This result is incorrect; it would correspond to **18 deaths** out of 60 cases, not the reported 12 deaths. - A calculation error yielding **30%** does not align with the standard formula for CFR using the given figures. *40%* - This percentage represents a CFR where **24 deaths** were reported among 60 cases, which is double the actual number of fatalities. - Such a high error suggests a significant misapplication of the **CFR formula**. *10%* - This value is incorrect; **10%** CFR would be obtained if only **6 deaths** occurred (6/60 * 100). - This result significantly underestimates the **Case Fatality Rate** as it is half of the calculated actual rate.

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

Question 1

A person's father had colon cancer. He had bloody stool. So, he just came for a check-up. Before he had not undergone any screening. He was recommended to do a colonoscopy for screening. Screening is which level of prevention?

Accepted Answer

Secondary

Answer

Tertiary

Answer

Primary

Answer

Primordial

Question 2

A total of 60 patients were diagnosed with COVID-19. Out of which, 12 deaths were reported. Calculate the Case Fatality Rate?

Accepted Answer

20%

Answer

40%

Answer

10%

Answer

30%

Question 3

Under IDSP, which diseases are included under sentinel surveillance?

Accepted Answer

HIV + HBV

Answer

Measles + Diphtheria

Answer

Malaria + Dengue

Answer

HIV + TB

Question 4

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 5

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 6

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 7

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 8

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 9

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

Accepted Answer

Primary prevention

Answer

Secondary prevention

Answer

Tertiary prevention

Answer

Primordial prevention

Question 10

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

Epidemiology — MCQs

Epidemiology — MCQs

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