Epidemiology Practice Questions

Q: In Africa, vaccination was given in an endemic outbreak area for a specific disease but due to shortage of vaccines, mass chemoprophylaxis treatment was given to people who were not diseased. Which type of prevention is this?

Specific protection. ***Specific protection*** - **Vaccination** directly prevents disease, fitting into the criteria of specific protection. - **Mass chemoprophylaxis** aims to prevent disease in healthy individuals in an endemic area, which is also a form of specific protection. *Rehabilitation* - This involves measures to restore function and well-being after a disease has occurred and caused disability. - It does not involve preventing the initial onset of disease, as described in the scenario. *Health promotion* - Health promotion includes broad interventions like education, lifestyle changes, and environmental modifications to improve overall health and prevent disease indirectly. - It is not as targeted as vaccination or chemoprophylaxis against a specific disease. *Early diagnosis and treatment* - This level of prevention focuses on identifying and treating a disease in its early stages to prevent its progression and complications. - The scenario describes preventing disease in healthy individuals, not treating existing cases.

Q: On republic day, a camp was organized and people were screened for Hypertension by checking BP and for diabetes by checking their BMI and Blood sugar level, which level of prevention is this?

Secondary. ***Secondary*** - This level of prevention focuses on **early detection** and prompt treatment of a disease to halt or slow its progression. - **Screening for hypertension and diabetes** through BP checks, BMI, and blood sugar levels aims to identify these conditions in their early stages before overt symptoms appear. *Tertiary* - This level of prevention involves measures to **reduce the impact** of an established disease, prevent complications, and improve quality of life. - Examples include rehabilitation programs or medications for long-term disease management, which are not described in the scenario. *Primary* - This level of prevention aims to **prevent a disease from occurring** in the first place, typically by addressing risk factors. - Examples include vaccination, health education on healthy eating, or promoting physical activity to prevent the development of hypertension or diabetes. *Primordial* - This is the **earliest level of prevention**, targeting the underlying social, environmental, and economic conditions that contribute to risk factors for disease. - It involves interventions to *prevent the emergence of risk factors* in populations, such as broad public health policies or community-wide initiatives.

Q: What is the incubation period of hepatitis B?

45 - 180 days. ***45 - 180 days*** - The typical incubation period for **Hepatitis B** infection ranges from **45 to 180 days** (approximately 6 weeks to 6 months). - This relatively long incubation period is characteristic of the **Hepadnaviridae family** to which HBV belongs. *1 - 30 days* - This period is generally too short for **Hepatitis B** and is more typical for certain **bacterial or viral respiratory illnesses**. - It does not align with the known epidemiology and viral replication cycle of **HBV**. *2 weeks - 6 months* - While **6 months** falls within the upper range, the lower limit of **2 weeks** (14 days) is generally too short for the typical incubation period of Hepatitis B. - The more precise range starts closer to **6 weeks (42 days)**. *15 - 45 days* - This range is too short for the common incubation period of **Hepatitis B**. - This period is more commonly associated with other viral infections, such as **Hepatitis A**.

Q: In a disease with 100% mortality, what is the relationship between incidence and prevalence?

Prevalence is less than incidence (P < I). ***Prevalence is less than incidence (P < I)*** - In a disease with 100% mortality, all affected individuals will eventually die, meaning their contribution to the **prevalent pool is temporary** or non-existent in the long run. - While new cases (incidence) continue to arise, the rapid removal of cases due to death prevents the buildup of prevalent cases, thus keeping prevalence lower than incidence. *Prevalence equals incidence (P = I)* - This scenario would imply that every new case immediately disappears or that the disease has no duration, which contradicts the concept of **disease progression** and death. - **Prevalence** is influenced by both the incidence rate and the duration of the disease; if duration is effectively zero due to immediate death, the relationship still leans towards prevalence being lower. *There is no relationship between prevalence and incidence* - This statement is incorrect as **incidence and prevalence are fundamentally linked**. Prevalence is a function of incidence and disease duration. - Changes in incidence directly affect **prevalence**, although the extent of this effect is modulated by factors like disease duration, recovery, or mortality. *Prevalence is greater than incidence (P > I)* - Prevalence being greater than incidence typically occurs in **chronic diseases** where individuals live with the condition for a long time, allowing prevalent cases to accumulate. - With **100% mortality**, individuals do not survive long enough to contribute significantly to the prevalent pool, making it impossible for prevalence to exceed incidence in this context.

Q: Base population for a population based cancer registry is:-

1-5 million. ***1-5 million*** - A population-based cancer registry aims to collect data on all cancer cases within a defined geographical area to estimate population-level incidence and mortality rates. To accurately capture these rates and allow for meaningful statistical analysis, the base population needs to be large enough to generate a sufficient number of cases. Most sources recommend a population of **at least 1 million** to achieve stable incidence rates. The upper limit of **5 million** ensures that the registry remains manageable in terms of data collection and quality control, while still providing a robust sample for epidemiological studies. *1-2 million* - While a population of 1-2 million might be adequate for some registries, most established guidelines suggest a broader range up to **5 million** for optimal statistical power and representativeness. - Limiting the upper bound to 2 million might restrict the ability to capture a diverse range of cancer cases and risk factors across a larger population. *2-7 million* - A population range of 2-7 million is generally an acceptable size for a population based cancer registry. However, the most commonly cited and widely accepted range in public health practice for optimal balance between statistical power and logistical feasibility is **1-5 million**. - A population exceeding 5 million can sometimes pose challenges in terms of resource allocation and data management for comprehensive registry operations. *1-3 million* - Similar to 1-2 million, a range of 1-3 million is a reasonable starting point, but the optimal and most widely recognized range extends up to **5 million**. - This narrower range might not fully leverage the benefits of a larger population for more robust epidemiological studies and rare cancer surveillance.

Q: In a village of 100 children, 60% are immunized against measles. One child travelled outside and returned with measles and infected other 26 children. What is the secondary attack rate

67%. ***Correct: 67%*** - The **secondary attack rate** is calculated by: **(Number of Secondary Cases / Number of Susceptible Contacts) × 100** - There are 100 children total, with 60% immunized, meaning **60 children are immune** and **40 children are susceptible** - One child traveled with measles (the **index/primary case**), leaving **39 susceptible contacts** (40 - 1 = 39) - **26 new secondary cases** occurred among the 39 susceptible contacts - Calculation: **(26 / 39) × 100 = 66.67% ≈ 67%** *Incorrect: 65%* - This results from incorrectly including the index case in the denominator: (26/40) × 100 = 65% - The index case is the **primary case**, not a susceptible contact, so should be excluded from the denominator *Incorrect: 80%* - This percentage does not align with the given numbers - Would require either more secondary cases or fewer susceptible contacts than provided in the scenario *Incorrect: 27%* - This significantly underestimates the secondary attack rate - Likely results from using the **total population (100)** as denominator instead of susceptible contacts: (26/100) × 100 = 26%

Q: All of the following are methods of health promotion except:

Immunization. ***Immunization (Correct - This is the EXCEPTION)*** - Immunization is primarily a form of **specific protection** under primary prevention, NOT a health promotion strategy - While essential for **disease prevention**, it targets specific diseases rather than enabling broad lifestyle improvements - Health promotion focuses on **non-specific measures** that enable people to increase control over and improve their overall health *Behavioral changes (Incorrect - This IS health promotion)* - Promoting **positive behavioral changes** (e.g., increased physical activity, smoking cessation) is a **core component of health promotion** - These changes empower individuals to adopt healthier lifestyles and reduce disease risk through non-specific measures *Nutritional education (Incorrect - This IS health promotion)* - **Educating individuals** and communities about healthy eating habits is a **fundamental aspect of health promotion** - It helps prevent diet-related diseases and improves overall well-being through lifestyle modification *Health education (Incorrect - This IS health promotion)* - Providing accessible and understandable **health information** is a **key method of health promotion** - This knowledge empowers individuals to make informed decisions about their health and adopt healthier behaviors

Q: Which of the following is the best parameter to predict virulence of acute infectious illness?

Case fatality rate. ***Case fatality rate*** - The **case fatality rate (CFR)** directly measures the **proportion of individuals diagnosed with a disease who die from it**, reflecting the pathogen's ability to cause death. - A higher CFR indicates greater **virulence** and a more severe disease outcome, making it the most direct predictor of an illness's ability to harm. *Incidence* - **Incidence** measures how often a disease occurs in a population over a specified period, indicating the **risk of contracting the disease**. - It does not provide information about the **severity** or **lethality** of the disease once contracted. *Secondary attack rate* - The **secondary attack rate** quantifies the probability that infection will occur among susceptible individuals within a particular group exposed to a primary case. - While it measures **transmissibility** and the potential for spread within a close group, it does not reflect the **virulence** or severity of the illness itself. *Crude death rate* - The **crude death rate** is the total number of deaths from all causes in a population over a given period, divided by the total population. - This parameter measures **overall mortality** in a population and is not specific to the deaths caused by a particular infectious illness, nor does it solely reflect its virulence.

Q: If a new effective treatment is initiated for a communicable disease and all the other factors remain the same, which of the following is most likely to happen?

Prevalence will change but incidence will not change. ***Prevalence will change but incidence will not change*** - **Incidence** refers to the rate of NEW cases occurring in a population over time - Treatment does NOT prevent new cases from occurring; it only treats existing cases - Therefore, **incidence remains unchanged** when treatment is introduced (assuming all other factors like exposure, transmission, and susceptibility remain constant) - **Prevalence** = Incidence × Duration of disease - Effective treatment **shortens disease duration** by curing patients faster or preventing progression - This directly **reduces the number of existing cases**, thereby **decreasing prevalence** - This is the classic epidemiological principle: **treatment affects prevalence, prevention affects incidence** *Incidence and prevalence both will change* - This would be incorrect for treatment alone - While effective treatment might have secondary effects on transmission in some communicable diseases, the **primary and direct effect is on prevalence only** - To reduce incidence, you need **primary prevention measures** (vaccination, vector control, reducing exposure) not treatment - The question specifically states "all other factors remain the same," meaning transmission dynamics are unchanged *Incidence will not change* - This statement alone is incomplete as it doesn't address prevalence - While correct that incidence won't change, this option fails to indicate what happens to prevalence *Neither incidence nor prevalence will change* - This is completely incorrect - Effective treatment must reduce prevalence by shortening disease duration and curing existing cases - If neither changed, the treatment would be ineffective by definition

Q: The time interval between the receipt of infection by a host and the time when the host becomes infectious is known as–

latent period. ***latent period*** - The **latent period** refers to the time from infection until the individual **first becomes infectious** to others. - During this period, the pathogen replicates within the host but has not yet reached a level where it can be transmitted. - This is distinct from the incubation period, which is the time from infection to onset of symptoms. - An individual may be infectious before, during, or after becoming symptomatic depending on the disease. *serial interval* - The **serial interval** is the duration between the onset of symptoms in a primary case and the onset of symptoms in a secondary case who was infected by the primary case. - It describes the time course of disease transmission from one person to another in a chain of transmission. *quarantine period* - The **quarantine period** is the time during which an individual suspected of being exposed to a communicable disease is isolated to prevent potential transmission. - It aims to monitor for symptoms and ensure that the person does not spread the disease if they become ill. *generation time* - In epidemiology, the **generation time** is the time between infection in a primary case and infection in a secondary case. - This differs from serial interval which measures time between symptom onsets rather than infection times.

Question 1

In Africa, vaccination was given in an endemic outbreak area for a specific disease but due to shortage of vaccines, mass chemoprophylaxis treatment was given to people who were not diseased. Which type of prevention is this?

Accepted Answer

Specific protection

Answer

Rehabilitation

Answer

Health promotion

Answer

Early diagnosis and treatment

Question 2

On republic day, a camp was organized and people were screened for Hypertension by checking BP and for diabetes by checking their BMI and Blood sugar level, which level of prevention is this?

Accepted Answer

Secondary

Answer

Tertiary

Answer

Primary

Answer

Primordial

Question 3

What is the incubation period of hepatitis B?

Accepted Answer

45 - 180 days

Answer

1 - 30 days

Answer

2 weeks - 6 months

Answer

15 - 45 days

Question 4

In a disease with 100% mortality, what is the relationship between incidence and prevalence?

Accepted Answer

Prevalence is less than incidence (P < I)

Answer

Prevalence equals incidence (P = I)

Answer

There is no relationship between prevalence and incidence

Answer

Prevalence is greater than incidence (P > I)

Question 5

Base population for a population based cancer registry is:-

Accepted Answer

1-5 million

Answer

1-2 million

Answer

2-7 million

Answer

1-3 million

Question 6

In a village of 100 children, 60% are immunized against measles. One child travelled outside and returned with measles and infected other 26 children. What is the secondary attack rate

Accepted Answer

67%

Answer

65%

Answer

80%

Answer

27%

Question 7

All of the following are methods of health promotion except:

Accepted Answer

Immunization

Answer

Behavioral changes

Answer

Nutritional education

Answer

Health education

Question 8

Which of the following is the best parameter to predict virulence of acute infectious illness?

Accepted Answer

Case fatality rate

Answer

Incidence

Answer

Secondary attack rate

Answer

Crude death rate

Question 9

If a new effective treatment is initiated for a communicable disease and all the other factors remain the same, which of the following is most likely to happen?

Accepted Answer

Prevalence will change but incidence will not change

Answer

Neither incidence nor prevalence will change

Answer

Incidence will not change

Answer

Incidence and prevalence both will change

Question 10

The time interval between the receipt of infection by a host and the time when the host becomes infectious is known as–

Accepted Answer

latent period

Answer

serial interval

Answer

quarantine period

Answer

generation time

Epidemiology — MCQs

Epidemiology — MCQs

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