Epidemiology — MCQs

Epidemiology Indian Medical PG Practice Questions and MCQs

Question 1631: Which of the following diseases is not under surveillance in the Integrated Disease Surveillance Project (P-Form)?

A. Snake bite (Correct Answer)
B. Acute respiratory tract infections
C. Tuberculosis
D. Leptospirosis

Explanation: ***Snake bite*** - While a public health concern, **snake bites** are generally not included in the list of diseases under routine surveillance by the Integrated Disease Surveillance Project (IDSP) P-Form, which focuses on infectious diseases with epidemic potential. - The IDSP primarily monitors for **communicable diseases**, outbreaks, and other public health threats requiring rapid detection and response. *Acute respiratory tract infections* - **Acute respiratory tract infections (ARIs)**, including severe acute respiratory infections (SARIs), are a major focus of IDSP surveillance due to their high transmissibility and potential for large-scale outbreaks. - Surveillance helps in detecting trends, identifying new pathogens, and implementing timely control measures. *Tuberculosis* - **Tuberculosis (TB)** is a priority disease for surveillance under the IDSP due to its high prevalence, chronic nature, and the need for continuous monitoring of incidence, prevalence, and treatment outcomes. - The IDSP plays a role in tracking TB cases and drug resistance patterns to inform national control programs. *Leptospirosis* - **Leptospirosis** is an emerging infectious disease with epidemic potential, especially in areas with poor sanitation and during floods, making it a crucial disease for IDSP surveillance. - Surveillance helps in early detection of outbreaks and implementation of control measures to prevent spread.

Question 1632: Most common nosocomial infection is

A. Gastrointestinal tract infection
B. Respiratory tract infection
C. Throat infection
D. Urinary tract infection (Correct Answer)

Explanation: ***Urinary tract infection*** - **Urinary tract infections (UTIs)** are the most prevalent type of Healthcare-Associated Infections (HAIs) due to the frequent use of **urinary catheters** in hospitalized patients. - Catheterization provides a direct route for bacteria to enter the bladder and ascend to the kidneys, increasing the risk of infection. *Gastrointestinal tract infection* - While **gastrointestinal infections** can be nosocomial, often due to organisms like *Clostridioides difficile*, they are not the most common overall. - **Diarrhea outbreaks** are significant but less frequent than UTIs across all hospital settings. *Respiratory tract infection* - **Respiratory tract infections**, such as **hospital-acquired pneumonia (HAP)**, are serious but rank second or third in prevalence among HAIs. - Risk factors often include mechanical ventilation and compromised lung function. *Throat infection* - **Throat infections** (pharyngitis) are rarely a primary nosocomial infection type. - They are more common as community-acquired infections and less significant in overall HAI statistics.

Question 1633: According to Hill's criteria, which of the following is NOT a criterion for establishing causality in noncommunicable diseases?

A. Strength of association
B. Absence of temporal sequence (Correct Answer)
C. Dose response relationship
D. Specificity of association

Explanation: ***Absence of temporal sequence*** - A crucial criterion for establishing causality is the **presence of a temporal sequence**, meaning the exposure must precede the outcome. - The **absence of a temporal sequence** would argue directly against causality, as the cause cannot come after the effect. *Strength of association* - This criterion suggests that a **stronger statistical association** between an exposure and an outcome makes a causal relationship more likely. - A large **relative risk** or **odds ratio** indicates a strong association. *Dose response relationship* - This criterion implies that as the **amount or duration of exposure increases**, the **risk or severity of the outcome also increases**. - This **dose-response gradient** strengthens the argument for a causal link. *Specificity of association* - This criterion suggests that a single exposure leads to a **specific effect**, and not a wide range of unrelated effects. - While helpful, **lack of specificity does not rule out causality**, as many exposures can have multiple effects.

Question 1634: Time interval between invasion of the infectious agent and appearance of the first sign or symptom?

A. Serial interval
B. Incubation period (Correct Answer)
C. Quarantine
D. Period of infectivity

Explanation: ***Incubation period*** - This is the definition of the **incubation period**: the time between exposure to an infectious agent and the onset of the first signs or symptoms of the disease. - During this period, the pathogen is **multiplying within the host** but has not yet reached a critical mass or caused enough damage to manifest clinically. *Serial interval* - The **serial interval** is the time between the onset of symptoms in a primary case and the onset of symptoms in a secondary case infected by the primary case. - It is a measure related to disease transmission dynamics, not an individual's progression from infection to symptoms. *Quarantine* - **Quarantine** is a restriction on the movement of people or goods which is intended to prevent the spread of disease or pests. - It is a public health intervention, not a temporal period describing disease progression within an individual. *Period of infectivity* - The **period of infectivity** refers to the time during which an infected individual is capable of transmitting the infectious agent to others. - This period can overlap with the incubation period, symptomatic phase, or even occur during convalescence, but it is distinct from the time to symptom onset.

Question 1635: What is the chance of HIV infection after needle prick injury?

A. 1/300 (Correct Answer)
B. 1/100
C. 1/10000
D. 1 in 1 Lakh

Explanation: ***1/300*** - The risk of **HIV transmission** from a percutaneous exposure (e.g., needlestick) from an HIV-infected source is estimated to be approximately **0.3%**, or **1 in 300** - This is the **established standard risk** based on CDC and WHO occupational safety guidelines - Risk factors that may increase transmission include **deeper injury**, **larger blood volume**, **hollow-bore needle**, **visible blood on device**, and **high viral load** in the source patient *1/100* - This represents a **higher risk (1%)** than typically observed for occupational HIV needlestick injuries - The 1/100 risk is more commonly associated with **Hepatitis C virus (HCV)** transmission after percutaneous exposure, which has significantly higher infectivity than HIV *1/10000* - This represents a **significantly lower risk (0.01%)** than the established average for HIV transmission via needlestick injury - This underestimates the actual occupational risk and could lead to inadequate post-exposure prophylaxis measures *1 in 1 Lakh (1/100,000)* - This represents an **extremely low probability (0.001%)** of transmission, far below the known risk of HIV infection via needlestick - Such a remote risk would be more appropriate for **mucocutaneous exposures** or **intact skin contact**, not percutaneous injuries

Question 1636: Healthy carriers are seen in all except ?

A. Cholera
B. Measles (Correct Answer)
C. Meningococci
D. Polio

Explanation: ***Measles (Correct Answer)*** - Measles does **NOT** have a healthy carrier state, making it the correct answer to this EXCEPT question. - Individuals are infectious during the **prodromal phase** and **rash stage**, but the virus is **completely eliminated** from the body after recovery. - Recovery confers **lifelong immunity** with no asymptomatic carriage. *Cholera (Incorrect)* - Individuals infected with *Vibrio cholerae* can become **asymptomatic carriers** and continue to shed bacteria in their feces for weeks after symptomatic recovery. - These carriers play a significant role in the **transmission and persistence of cholera outbreaks**. *Meningococci (Incorrect)* - A substantial proportion of the population (5-10%) can carry *Neisseria meningitidis* asymptomatically in the **nasopharynx** without developing disease. - These **healthy carriers** are a common source of infection for susceptible individuals. *Polio (Incorrect)* - Many individuals infected with poliovirus experience only mild or asymptomatic illness but can still **shed the virus in their stools** for weeks. - These **asymptomatic carriers** can transmit polio, making eradication efforts challenging.

Question 1637: Denominator in crude death rate is

A. Mid-year married females 15-44 years
B. Mid-year population (Correct Answer)
C. Mid-year males 15-44 years
D. Mid-year females 15-44 years

Explanation: ***Mid-year population*** - The **crude death rate** is a measure of the overall mortality in a population, calculated as the total number of deaths in a given period divided by the estimated **mid-year population** for that same period. - The **mid-year population** is used as the denominator to represent the population at risk of dying during the entire year, accounting for population changes due to births, deaths, and migration. *Mid-year married females 15-44 years* - This specific demographic group would be the denominator for rates related to **maternal mortality** or **fertility rates**. - It is too specific to represent the entire population at risk needed for the **crude death rate**. *Mid-year males 15-44 years* - This is a **sex- and age-specific population group** and would be used as the denominator for **age- and sex-specific death rates**. - It does not represent the total population at risk of death across all ages and sexes. *Mid-year females 15-44 years* - Similar to the male-specific group, this is an **age- and sex-specific population group**. - While relevant for certain demographic studies, it is not the appropriate denominator for the **crude death rate**, which considers the entire population.

Question 1638: Which of the following vectors has a habit of frequent vomiting?

A. House fly (Correct Answer)
B. Mite
C. Sand flea
D. Mosquito

Explanation: ***House fly*** - The **house fly** (Musca domestica) is known for its habit of **regurgitating** its gut contents (vomiting) onto food before ingesting it, as part of a regurgitative feeding strategy. - This behavior aids in the external digestion of solid food particles into a liquid form that the fly can then suck up. *Mite* - **Mites** are typically **arachnids** and do not feed by vomiting; their feeding habits vary greatly depending on the species, but typically involve piercing and sucking fluids. - They lack the organ systems for regurgitative feeding similar to that of a house fly. *Sand flea* - **Sand fleas** (Tunga penetrans) are ectoparasites that **burrow into the skin** of their hosts, where they feed and lay eggs. - Their feeding mechanism involves piercing the host's skin to feed on blood or tissue, and they do not exhibit vomiting behavior. *Mosquito* - **Mosquitoes** are known for their **sucking mouthparts**, which they use to feed on blood or plant nectar. - While they can regurgitate saliva during feeding, this is distinct from the frequent, digestive vomiting habit of a house fly.

Question 1639: All the following are true about nosocomial infections except -

A. May develop after discharge of patient from the hospital
B. May already present at the time of admission (Correct Answer)
C. Denote a new condition which is unrelated to the patient's primary conditions
D. May manifest 48 hours or more after admission

Explanation: ***May already present at the time of admission*** - This statement is **incorrect** because a **nosocomial infection** is defined as an infection acquired in a hospital or healthcare setting, meaning it was **not present** or incubating at the time of admission. - If an infection is present upon admission, it is considered a **community-acquired infection**, not nosocomial. *May develop after discharge of patient from the hospital* - Nosocomial infections can indeed **manifest after discharge**, especially for infections with longer incubation periods or those related to procedures or devices. - For example, a surgical site infection might not become apparent until several days or weeks after discharge (within 30 days for most infections, or up to 90 days for certain surgical site infections). *May manifest 48 hours or more after admission* - An infection is considered nosocomial if it appears **48 hours or more** after hospital admission. - This is the standard criterion to differentiate hospital-acquired infections from community-acquired infections that were incubating at the time of admission. *Denote a new condition which is unrelated to the patient's primary conditions* - Nosocomial infections are **new infections** that arise during the hospital stay and are not directly related to the patient's existing primary diagnosis. - While a patient's underlying condition might make them **more susceptible**, the infection itself is distinct and newly acquired from the healthcare environment.

Question 1640: An infectious disease shows iceberg phenomenon. That means it has -

A. More complications
B. More case fatality rate
C. More subclinical cases (Correct Answer)
D. More SAR

Explanation: ***More subclinical cases*** - The **iceberg phenomenon** illustrates that for many diseases, especially infectious ones, the majority of cases are **subclinical** or undiagnosed. - Only a small fraction of cases present with **clinical symptoms** and are thus observed ("the tip of the iceberg"). *More complications* - While some infectious diseases develop complications, the **iceberg phenomenon** specifically refers to the disparity between apparent cases and the larger pool of unapparent infections, not primarily the severity of complications. - The presence of complications usually falls within the "tip" of the iceberg, representing clinically apparent disease. *More case fatality rate* - The **case fatality rate (CFR)** is the proportion of individuals diagnosed with a disease who die from it. - The **iceberg phenomenon** does not directly comment on mortality rates but rather on the prevalence of unapparent infections. *More SAR* - **SAR** stands for **secondary attack rate**, which is the probability that infection occurs among susceptible individuals after exposure to an infected primary case. - The **iceberg phenomenon** describes the overall distribution of clinical versus subclinical cases in a population and is not directly related to the rate of secondary infections.

Practice by Chapter

Principles of Epidemiology

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Measures of Disease Frequency

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Epidemiological Study Designs

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Descriptive Epidemiology

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Analytical Epidemiology

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Experimental Epidemiology

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Screening for Disease

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Surveillance Systems

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Investigation of an Epidemic

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Association and Causation

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Modern Epidemiological Methods

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Critical Appraisal of Epidemiological Studies

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