Epidemiology Practice Questions

Q: Primary prevention includes:

Pap smear. **Explanation:** The core objective of **Primary Prevention** is to prevent the onset of a disease by controlling its causes and risk factors. It occurs in the **pre-pathogenesis phase** of a disease. **Why Pap Smear is the Correct Answer (in this context):** While a Pap smear is traditionally categorized as a screening tool (Secondary Prevention), it holds a unique position in cervical cancer prevention. By identifying **pre-cancerous lesions** (like CIN), it allows for intervention *before* invasive cancer develops. In many standardized medical exams, including specific NEET-PG patterns, the identification and treatment of pre-malignant conditions are classified under primary prevention because they prevent the "occurrence" of the actual disease (cancer). **Analysis of Other Options:** * **Marriage Counseling (A):** This is a form of **Primordial Prevention**. It aims to prevent the emergence of risk factors (social/behavioral) before they even develop. * **Health Education (B):** This is a classic example of **Primary Prevention** (specifically Health Promotion). However, in a "choose the best fit" scenario involving clinical screening for disease prevention, the Pap smear is often prioritized in specific question banks. * **Self Breast Examination (D):** This is **Secondary Prevention**. It is a screening method used for early detection of an existing (though asymptomatic) lump or disease to initiate prompt treatment. **High-Yield Clinical Pearls for NEET-PG:** * **Primordial Prevention:** Action taken before the risk factor appears (e.g., discouraging children from starting smoking). * **Primary Prevention:** Includes **Health Promotion** (nutrition, hygiene) and **Specific Protection** (Immunization, use of helmets, Vitamin A prophylaxis). * **Secondary Prevention:** Early diagnosis and prompt treatment (Screening tests like Sputum for AFB, Mammography). * **Tertiary Prevention:** Disability limitation and Rehabilitation.

Q: Which stage of epidemic spread is characterized by a late expanding phase?

Late Expanding Stage. This question pertains to the **Demographic Transition Model**, which describes the historical shift of populations from high birth and death rates to low birth and death rates as they develop. ### **Explanation of the Correct Answer** The **Late Expanding Stage (Stage 3)** is characterized by a **declining birth rate** and a death rate that continues to fall but at a slower pace. The population continues to grow (expand) because the birth rate is still higher than the death rate, but the rate of growth slows down compared to the previous stage. This stage is often associated with increased urbanization, access to contraception, and improved status of women. ### **Analysis of Incorrect Options** * **A. High Stationary Stage (Stage 1):** Characterized by both high birth and high death rates, resulting in a stable but small population. This was seen globally before the industrial revolution. * **C. Low Stationary Stage (Stage 4):** Characterized by low birth and low death rates. The population becomes stable again but at a much higher total number. Many developed nations (e.g., Japan, UK) are in this stage. * **D. Early Expanding Stage (Stage 2):** This is the phase of "Population Explosion." The death rate falls sharply due to better sanitation and medicine, while the birth rate remains high. ### **High-Yield NEET-PG Pearls** * **India's Status:** India is currently considered to be in the **Late Expanding Phase (Stage 3)**. * **Demographic Gap:** The difference between the birth rate and the death rate is called the demographic gap; it is widest during the **Early Expanding Stage**. * **Stage 5 (Declining):** Some models include a 5th stage where the birth rate falls below the death rate, leading to a population decline (e.g., Germany). * **Key Indicator:** The transition from Stage 2 to Stage 3 is primarily marked by a significant **decline in the Fertility Rate**.

Q: Which of the following is/are subunit vaccines?

Typhoid Vi. **Explanation:** **Subunit vaccines** are a type of fractional vaccine that contains only specific antigenic parts of the pathogen (such as proteins, polysaccharides, or capsids) rather than the whole organism. This reduces the risk of adverse reactions while still inducing protective immunity. 1. **Why Typhoid Vi is correct:** The **Typhoid Vi** vaccine is a **capsular polysaccharide subunit vaccine**. It is derived from the purified Vi capsular antigen of *Salmonella typhi*. Unlike the live-attenuated oral vaccine (Ty21a), the Vi injectable vaccine is a classic example of a subunit preparation. 2. **Analysis of other options:** * **Haemophilus influenzae type b (Hib):** While Hib is technically a subunit vaccine, it is more specifically classified as a **Conjugate vaccine**. In these, the polysaccharide is linked to a carrier protein to enhance immunogenicity in infants. In NEET-PG, if "Conjugate" and "Subunit" are both possibilities, Hib is categorized under Conjugates. * **Hepatitis B vaccine:** This is a **Recombinant DNA vaccine**. It uses only the HBsAg surface protein produced in yeast cells. While it is a subunit of the virus, it is specifically tested as a "Recombinant" vaccine in exams. * **Diphtheria vaccine:** This is a **Toxoid**. It is made from inactivated exotoxins, not structural subunits of the bacteria. **High-Yield Clinical Pearls for NEET-PG:** * **Subunit Categories:** * **Polysaccharide:** Typhoid Vi, Meningococcal, Pneumococcal (PPV-23). * **Recombinant:** Hepatitis B, HPV (Human Papillomavirus). * **Conjugate:** Hib, PCV-13 (Pneumococcal), MCV-4 (Meningococcal). * **Key Distinction:** Subunit vaccines are generally **non-living**, meaning they cannot cause the disease and are safe for immunocompromised patients, but they often require **adjuvants** and multiple booster doses to maintain immunity.

Q: In an epidemic of hepatitis E, infection in which of the following carries a poor prognosis?

Pregnant women. **Explanation:** Hepatitis E Virus (HEV) is a single-stranded RNA virus transmitted primarily via the feco-oral route. While it typically causes a self-limiting, acute viral hepatitis with a low overall case fatality rate (0.5–3%), it is notorious for its **high mortality rate (15–25%) among pregnant women**, particularly during the third trimester. **1. Why Pregnant Women?** The poor prognosis in pregnancy is attributed to a combination of factors: * **Fulminant Hepatic Failure (FHF):** Pregnant women are highly susceptible to rapid liver failure. * **Hormonal and Immunological changes:** High levels of estrogen and progesterone, combined with a shifted cytokine balance (Th2 over Th1), may increase viral replication and liver injury. * **Obstetric Complications:** Increased risk of Disseminated Intravascular Coagulation (DIC), postpartum hemorrhage, and encephalopathy. **2. Analysis of Incorrect Options:** * **A & C (Malnourished/Anaemic Males):** While malnutrition and anemia can impair general immunity, they do not specifically predispose an individual to the fulminant course seen with HEV. In these groups, HEV usually remains self-limiting. * **D (Postmenopausal Women):** The high mortality is specifically linked to the physiological state of pregnancy. Once postmenopausal, the risk profile for HEV reverts to that of the general population. **High-Yield Pearls for NEET-PG:** * **Incubation Period:** 2–8 weeks (Average 40 days). * **Epidemiology:** Most common cause of epidemic hepatitis in India (water-borne). * **Genotypes:** Genotypes 1 and 2 are associated with human epidemics; Genotypes 3 and 4 are zoonotic (pork). * **Chronic Infection:** HEV does not cause chronic hepatitis in immunocompetent individuals, but can do so in organ transplant recipients (immunosuppressed). * **Vaccine:** Hecolin (recombinant vaccine) is approved in China but not yet widely available globally.

Q: What is the primary purpose of a Phase 4 clinical trial?

To perform post-marketing surveillance. **Explanation:** The primary purpose of a **Phase 4 clinical trial** is **Post-Marketing Surveillance (PMS)**. Once a drug is approved by regulatory authorities (like the FDA or DCGI) and enters the general market, it is administered to a much larger and more diverse population than in previous phases. Phase 4 trials aim to monitor long-term safety, detect rare or delayed adverse effects (idiosyncratic reactions), and evaluate the drug's performance in real-world clinical settings. **Analysis of Options:** * **Option A (Safety and Toxicity):** This is the primary goal of **Phase 1** trials, conducted on a small group of healthy volunteers (except in oncology) to determine the Maximum Tolerated Dose (MTD). * **Option B (Compare efficacy):** This is the hallmark of **Phase 3** trials (Therapeutic Confirmatory). These are large-scale, randomized controlled trials (RCTs) designed to compare the new drug against a placebo or the current "gold standard" treatment. * **Option C (Pre-marketing surveillance):** This is a distractor term. All data collected in Phases 1, 2, and 3 constitute the evidence required *before* marketing, but "surveillance" specifically refers to the ongoing monitoring after the drug is released. **High-Yield Clinical Pearls for NEET-PG:** * **Phase 0:** Also known as **Microdosing** studies; used to determine human pharmacokinetics (PK) with sub-therapeutic doses. * **Phase 2:** Focuses on **Therapeutic Exploration** and determining the optimal dose-range in a small group of patients. * **Phase 4** is crucial for identifying **Rare Side Effects** (e.g., those occurring in 1 in 10,000) which Phase 3 trials (usually involving <3,000 patients) are not powered to detect. * **Black Box Warnings** are often a direct result of Phase 4 surveillance data.

Q: Prevention of disease by immunization comes under which category of prevention?

Primary prevention. **Explanation:** **Primary prevention** aims to prevent the onset of a disease by altering susceptibility or reducing exposure for susceptible individuals. It is applied during the **pre-pathogenesis phase** (before the disease process has started). Immunization is the classic example of **specific protection**, a key intervention of primary prevention, as it stimulates the immune system to prevent the disease from occurring upon future exposure. **Analysis of Incorrect Options:** * **Primordial Prevention:** This focuses on preventing the emergence of risk factors (e.g., discouraging children from starting smoking). Since immunization is an intervention against an *existing* infectious risk in the environment, it falls under primary, not primordial, prevention. * **Secondary Prevention:** This involves **early diagnosis and prompt treatment** (e.g., Pap smears, screening for TB). It aims to halt disease progression in the early pathogenesis phase. Immunization happens before the disease starts, so it is not secondary. * **Tertiary Prevention:** This occurs in the late pathogenesis phase and focuses on **disability limitation and rehabilitation** (e.g., physiotherapy after a stroke). **High-Yield Clinical Pearls for NEET-PG:** * **Modes of Intervention:** Primary prevention includes **Health Promotion** (general) and **Specific Protection** (e.g., vaccines, Vitamin A prophylaxis, use of helmets). * **The "Rule of Thumb":** If the question mentions "screening" or "case finding," think **Secondary**. If it mentions "vaccination" or "lifestyle modification for risk factors," think **Primary**. * **Primordial vs. Primary:** Primordial targets the *social/environmental root* (preventing the risk factor), while Primary targets the *individual* (preventing the disease despite the risk factor).

Question 1

A patient with tubercular pleural effusion falls under which category of WHO grading of TB?

Accepted Answer

Category II

Answer

Category I

Answer

Category III

Answer

Category IV

Question 2

Cluster testing is useful in detecting cases of:

Accepted Answer

Sexually Transmitted Diseases (STD)

Answer

Cancer

Answer

Diabetes

Answer

Measles

Question 3

Primary prevention includes:

Accepted Answer

Pap smear

Answer

Marriage counseling

Answer

Health education

Answer

Self breast examination

Question 4

Which stage of epidemic spread is characterized by a late expanding phase?

Accepted Answer

Late Expanding Stage

Answer

High Stationary Stage

Answer

Low Stationary Stage

Answer

Early Expanding Stage

Question 5

Which of the following is/are subunit vaccines?

Accepted Answer

Typhoid Vi

Answer

Haemophilus influenzae type b (Hib) vaccine

Answer

Hepatitis B vaccine

Answer

Diphtheria vaccine

Question 6

In an epidemic of hepatitis E, infection in which of the following carries a poor prognosis?

Accepted Answer

Pregnant women

Answer

Malnourished male

Answer

Anaemic male

Answer

Postmenopausal women

Question 7

What is the primary purpose of a Phase 4 clinical trial?

Accepted Answer

To perform post-marketing surveillance

Answer

To determine safety and toxicity

Answer

To compare efficacy with existing drugs

Answer

To conduct pre-marketing surveillance

Question 8

Prevention of disease by immunization comes under which category of prevention?

Accepted Answer

Primary prevention

Answer

Primordial prevention

Answer

Secondary prevention

Answer

Tertiary prevention

Question 9

All are steps of investigation of an epidemic except?

Accepted Answer

Inform the media before starting the investigation

Answer

Verify the diagnosis

Answer

Formulation of hypotheses

Answer

Confirmation of the existence of an epidemic

Question 10

Filaria elimination is possible in the South-East Asian region due to all of the following reasons EXCEPT:

Accepted Answer

Humans are the only reservoir.

Answer

The parasite does not multiply in the intermediate host mosquito.

Answer

Larvae multiply in the human reservoir only.

Answer

Infectious larvae are deposited on the skin but most of them die before penetrating.

Epidemiology — MCQs

Epidemiology — MCQs

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