Epidemiology Practice Questions

Q: In a class of 100 students, 40 are susceptible to chickenpox. If 28 students developed chickenpox within the next 2 weeks, what is the secondary attack rate (SAR) of chickenpox?

70%. **70% - Correct Answer** The **secondary attack rate (SAR)** measures the spread of disease among susceptible contacts after exposure to a primary case. It is calculated as: **SAR = (Number of new cases among susceptible contacts / Total number of susceptible contacts) × 100%** In this scenario: - New cases = 28 students - Susceptible contacts = 40 students - SAR = (28/40) × 100% = **70%** This is the correct application of the SAR formula, using only susceptible individuals as the denominator (not the total class of 100). *60% - Incorrect* - This would require 24 out of 40 susceptible students developing chickenpox (24/40 = 0.60) - Does not match the observed 28 cases *80% - Incorrect* - This would require 32 out of 40 susceptible students developing chickenpox (32/40 = 0.80) - Overestimates the number of cases compared to the observed 28 *90% - Incorrect* - This would require 36 out of 40 susceptible students developing chickenpox (36/40 = 0.90) - Significantly overestimates the attack rate and does not reflect the actual 28 cases observed

Q: What is the primary purpose of taking sewer swabs in public health?

Typhoid carriers in the community. ***Typhoid carriers in the community*** - Sewer swabs are primarily used to detect the presence of **Salmonella Typhi** in sewage, indicating the presence of **asymptomatic carriers** shedding the bacteria. - This method helps identify populations where **typhoid fever** may silently spread or persist due to chronic carriers. *Active typhoid cases in the community* - While sewer swabs can indirectly indicate **active cases** due to increased shedding, their primary purpose is to identify **carriers** who might not be exhibiting symptoms. - **Clinical diagnosis** and **stool culture** from symptomatic individuals are more direct methods for identifying active typhoid cases. *Active cholera cases in the community* - Sewer swabs *can* detect **Vibrio cholerae**, the bacterium causing cholera, but this is not their primary use, especially when targeting **typhoid surveillance**. - **Cholera** outbreaks typically prompt targeted **water sample testing** and clinical surveillance due to their rapid onset and severity. *Cholera carriers in the community* - Similar to active cases, while possible to detect **Vibrio cholerae**, sewer swabs are not the primary tool specifically for identifying **cholera carriers**. - **Cholera carriers** are less common and their detection is usually part of broader environmental surveillance during or after an outbreak.

Q: Which of the following is an example of a case-control study that investigates the relationship between a risk factor and a disease?

All of the options. ***All of the options*** - **All three scenarios** represent classic examples of case-control studies in epidemiology, where investigators identified cases of disease and compared them to controls to determine past exposure to risk factors. - Case-control studies are **retrospective** in design, starting with the outcome (disease) and looking backward to identify exposure history. **Maternal smoking and congenital malformation** - Cases: Children with congenital malformations - Controls: Children without malformations - Exposure assessed: History of maternal smoking during pregnancy - This exemplifies the typical case-control approach to studying teratogenic exposures. **Thalidomide exposure and teratogenicity** - The landmark studies by **Lenz (1961)** and **McBride (1961)** were **case-control studies** - Cases: Infants with phocomelia (limb malformations) - Controls: Infants without malformations - They looked backward from the cases to identify thalidomide exposure during pregnancy - This rapid identification of the thalidomide-phocomelia link demonstrates the power of case-control methodology for rare outcomes. **Vaginal adenocarcinoma and intrauterine exposure to DES** - The classic **Herbst et al. (1971)** study was a **case-control study** - Cases: Young women with clear cell adenocarcinoma of the vagina - Controls: Age-matched women without the disease - They investigated past exposure and discovered the association with maternal DES use during pregnancy - This is a textbook example of case-control design for investigating rare diseases with long latency periods.

Q: What is the leading cause of accidental death in India?

Road traffic accidents. ***Road traffic accidents*** - Road traffic accidents are a major public health concern in India and contribute significantly to accidental deaths due to factors like poor road infrastructure, traffic law violations, and vehicle safety issues. - India has one of the highest numbers of road accident fatalities globally, with over 1.5 lakh deaths annually, making it the leading cause of accidental death. - According to National Crime Records Bureau (NCRB) data, RTAs account for the majority of accidental deaths in India. *Drowning (accidental death)* - While drowning is a significant cause of accidental death, particularly in areas prone to floods or with prevalent water bodies, it does not surpass road traffic accidents in overall numbers in India. - Drowning deaths often occur in specific contexts such as recreational activities, occupational hazards, or natural calamities. *Burn injuries* - Burn injuries are a common cause of accidental death, especially related to household accidents, industrial settings, and festivals in India. - However, the total number of deaths due to burn injuries is typically lower compared to the high incidence and fatality rates of road traffic accidents. *Poisoning (accidental death)* - Accidental poisoning can occur due to various substances, including pesticides, industrial chemicals, or pharmaceutical products, and can lead to death. - Despite being a notable cause of accidental fatalities, poisoning rates are generally lower than those attributed to road traffic accidents across India.

Q: A study is conducted using people who volunteer to participate. Which type of bias may occur?

Selection bias. ***Selection bias*** - **Selection bias** occurs when participants for a study are not chosen randomly, leading to groups that are not comparable. - In this scenario, individuals who **volunteer** for a randomized study may differ systematically from those who do not, affecting the generalizability of results. *Hawthorne effect bias* - The **Hawthorne effect** is a type of reactivity in which individuals modify an aspect of their behavior in response to their awareness of being observed. - This bias is related to the **observational setting** and the human response to being studied, rather than the initial selection of participants. *Berkson's bias* - **Berkson's bias** is a form of selection bias that results from differential rates of hospital admission for different diseases. - It arises in studies using hospitalized patients, where the **exposure-disease relationship** might be distorted compared to the general population. *Observer bias* - **Observer bias** (also known as ascertainment bias) occurs when researchers' expectations, beliefs, or preconceptions influence the observation or recording of data. - This bias relates to the **measurement or assessment of outcomes** by investigators, not the recruitment of study participants.

Q: What type of prevention does screening represent in public health?

Secondary prevention. ***Secondary prevention*** - **Screening** aims to **detect disease early** in asymptomatic individuals, allowing for prompt intervention and preventing disease progression. - This aligns with secondary prevention's goal of **reducing the impact of a disease** once it has occurred or is in its early stages. *Primordial prevention* - Focuses on **preventing the emergence of risk factors** for disease in the first place, often through broad public health policies. - It targets the entire population or specific groups to **avoid the development of unhealthy lifestyles or environmental conditions**. *Primary prevention* - Aims to **prevent the onset of disease** in healthy individuals by addressing risk factors or providing protective measures. - Examples include **vaccination** to prevent infectious diseases or promoting **healthy diets** to prevent cardiovascular disease. *Tertiary prevention* - Involves measures to **reduce the negative impact of an already established disease** by improving quality of life, reducing disability, and preventing complications. - This includes **rehabilitation, pain management**, and support groups for individuals living with chronic conditions.

Q: Which method is primarily used to detect cases that may not be identified through other surveillance techniques?

Active surveillance. ***Active surveillance*** - This method involves **proactive efforts by public health officials** to identify cases by directly contacting healthcare providers, visiting facilities, and actively searching for unreported cases. - It is specifically designed to **detect cases that may be missed** by passive reporting systems due to underreporting, lack of awareness, or incomplete reporting. - While resource-intensive, it ensures **comprehensive case detection** and is the gold standard for identifying all cases of diseases under surveillance, particularly during outbreak investigations. *Passive surveillance* - This method relies on **voluntary reporting** by healthcare providers to public health authorities. - It is inexpensive but often **misses cases** due to underreporting, making it the system that active surveillance is designed to supplement. *Sentinel surveillance* - This method uses **carefully selected reporting sites** (hospitals, clinics, or practitioners) to monitor disease trends and provide early warning signals. - It is designed for **monitoring specific diseases** efficiently and detecting emerging patterns, not primarily for finding cases missed by other methods. - Useful for resource-limited settings to track trends without comprehensive reporting. *Prevalence rate* - This is a **descriptive epidemiological measure** indicating the proportion of a population with a disease at a given time. - It is not a surveillance method but rather a **statistical measure** used to assess disease burden.

Q: NFHS-3 was conducted in?

2005-06. ***2005-06*** - The **National Family Health Survey (NFHS-3)** was indeed conducted during the period of **2005-2006**. - This survey provided crucial data on health and family welfare indicators across India. *1992-93* - This period corresponds to the **National Family Health Survey (NFHS-1)**, the first in the series. - It established baseline data for various health and demographic parameters in India. *1998-99* - This time frame marks the conduction of the **National Family Health Survey (NFHS-2)**. - NFHS-2 provided updated information and trends compared to NFHS-1. *2009-10* - While a significant health survey, this period does not correspond to NFHS-3. No NFHS survey was conducted then.

Q: Under which condition is screening IMPOSSIBLE (most fundamental criterion)?

Diseases with no latent period. ***Diseases with no latent period*** - This is the **MOST FUNDAMENTAL criterion** for screening - without a latent (presymptomatic) period, screening is **IMPOSSIBLE**, not just inefficient. - Screening is designed to detect diseases in their **presymptomatic phase** to allow for early intervention. - If symptoms appear immediately upon disease onset, there is **no detectable pre-clinical phase** to screen for. - This is a **Wilson-Jungner criterion** - the condition must have a recognizable latent or early symptomatic stage. *Prevalence of disease is low* - Low prevalence makes screening **inefficient and not cost-effective** due to low positive predictive value. - However, screening is still **theoretically possible**, just not recommended from a public health perspective. - This is an economic/efficiency criterion, not a fundamental feasibility criterion. *Life expectancy cannot be prolonged by early diagnosis* - If early treatment doesn't improve outcomes, screening lacks **benefit** but is still technically possible. - This relates to the **effectiveness of available treatment**, not the feasibility of screening itself. - Screening without treatment benefit violates the criterion that "there should be an accepted treatment for patients with recognized disease." *Diagnostic test is not available* - Without a suitable test, screening **cannot be performed**, but this is a **resource issue**, not a disease characteristic. - Once a test is developed, screening becomes possible. - The "no latent period" criterion is more fundamental as it relates to the **natural history of the disease** itself.

Question 1

In a class of 100 students, 40 are susceptible to chickenpox. If 28 students developed chickenpox within the next 2 weeks, what is the secondary attack rate (SAR) of chickenpox?

Accepted Answer

70%

Answer

60%

Answer

90%

Answer

80%

Question 2

What is the primary purpose of taking sewer swabs in public health?

Accepted Answer

Typhoid carriers in the community

Answer

Active typhoid cases in the community

Answer

Active cholera cases in the community

Answer

Cholera carriers in the community

Question 3

Which of the following is an example of a case-control study that investigates the relationship between a risk factor and a disease?

Accepted Answer

All of the options

Answer

Maternal smoking and congenital malformation

Answer

Thalidomide exposure and teratogenicity

Answer

Vaginal adenocarcinoma and intrauterine exposure to DES

Question 4

What is the leading cause of accidental death in India?

Accepted Answer

Road traffic accidents

Answer

Drowning (accidental death)

Answer

Burn injuries

Answer

Poisoning (accidental death)

Question 5

A study is conducted using people who volunteer to participate. Which type of bias may occur?

Accepted Answer

Selection bias

Answer

Hawthorne effect bias

Answer

Berkson's bias

Answer

Observer bias

Question 6

What type of prevention does screening represent in public health?

Accepted Answer

Secondary prevention

Answer

Primordial prevention

Answer

Primary prevention

Answer

Tertiary prevention

Question 7

Which method is primarily used to detect cases that may not be identified through other surveillance techniques?

Accepted Answer

Active surveillance

Answer

Passive surveillance

Answer

Sentinel surveillance

Answer

Prevalence rate

Question 8

NFHS-3 was conducted in?

Accepted Answer

2005-06

Answer

1992-93

Answer

1998-99

Answer

2009-10

Question 9

Cluster testing technique is useful in which of the following conditions?

Accepted Answer

Viral Meningitis

Answer

Rubella

Answer

Chickenpox

Answer

Sexually Transmitted Infections

Question 10

Under which condition is screening IMPOSSIBLE (most fundamental criterion)?

Accepted Answer

Diseases with no latent period

Answer

Prevalence of disease is low

Answer

Life expectancy cannot be prolonged by early diagnosis

Answer

Diagnostic test is not available

Epidemiology — MCQs

Epidemiology — MCQs

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