Epidemiology Practice Questions

Q: Who discovered the transmission of malaria by Anopheles mosquitoes?

Ronald Ross. **Explanation:** The correct answer is **Ronald Ross**. In 1897, while working in Secunderabad, India, Sir Ronald Ross discovered the presence of the malaria parasite within the gastrointestinal tract of an *Anopheles* mosquito. This landmark discovery proved that mosquitoes serve as the intermediate host and vector for the transmission of malaria, for which he was awarded the Nobel Prize in 1902. **Analysis of Options:** * **Laveran (Alphonse Laveran):** He was the first to observe the malaria parasite (*Plasmodium*) in the blood of a patient in 1880. He identified the causative agent, not the mode of transmission. * **Paul Muller:** He discovered the insecticidal properties of **DDT** (Dichlorodiphenyltrichloroethane) in 1939, which revolutionized malaria control through vector suppression. * **Pampana (Emilio Pampana):** A renowned malariologist known for his work on the global strategy for **Malaria Eradication** and author of the definitive textbook *A Textbook of Malaria Eradication*. **High-Yield Clinical Pearls for NEET-PG:** * **World Mosquito Day:** Observed on **August 20th** to commemorate Ronald Ross’s discovery. * **Definitive Host:** The mosquito is the definitive host for *Plasmodium* (where the sexual cycle occurs). * **Intermediate Host:** Humans are the intermediate host (where the asexual cycle occurs). * **Incubation Period:** For *P. falciparum*, it is typically 12 days; for *P. vivax*, it is 14 days. * **Drug of Choice:** For uncomplicated *P. falciparum* in India, the current protocol is **ACT** (Artesunate + Sulfadoxine-Pyrimethamine), except in North-Eastern states where AL (Artemether-Lumefantrine) is used.

Q: What method can be used to determine the prevalence of a condition at a single point in time?

Cross-sectional study. ### Explanation **Correct Answer: B. Cross-sectional study** A **Cross-sectional study** is often referred to as a "Snapshot Study" because it examines a population at a single point in time. In this study design, both the exposure and the outcome are measured simultaneously. Because it captures all existing cases (both old and new) at that specific moment, it is the primary method used to calculate **Prevalence**. #### Why other options are incorrect: * **A. Longitudinal study:** This involves repeated observations of the same variables over a long period. It is used to study the natural history of a disease or changes over time, rather than a single-point prevalence. * **C. Surveillance:** This is the continuous, systematic collection and analysis of health data for planning and evaluation. While it monitors trends, it is a process of ongoing "scrutiny" rather than a specific study design for point prevalence. * **D. Cohort study:** This is an observational, longitudinal study that follows a group from exposure to outcome. It is used to calculate **Incidence** (new cases) and determine relative risk, not prevalence. #### NEET-PG High-Yield Pearls: * **Prevalence vs. Incidence:** Cross-sectional studies measure Prevalence; Cohort studies measure Incidence. * **Directionality:** Cross-sectional studies have no direction (one-time look); Cohort studies are usually prospective (forward-looking). * **Limitation:** The biggest drawback of a cross-sectional study is the **"Chicken or Egg" dilemma** (Temporal Ambiguity)—it cannot establish a temporal relationship between exposure and outcome. * **Formula:** $Prevalence = \text{Incidence} \times \text{Mean Duration of Disease } (P = I \times D)$.

Q: Which vaccine is known to cause ITP as an adverse effect?

Typhoid vaccine. **Explanation:** **Immune Thrombocytopenic Purpura (ITP)** is a rare but recognized adverse event following immunization (AEFI). It occurs when the immune system produces antibodies that cross-react with platelets, leading to their destruction. **Why Typhoid Vaccine is the Correct Answer:** While several vaccines are associated with ITP, the **Typhoid vaccine** (specifically the older parenteral heat-phenol inactivated type) has been historically documented in literature and epidemiological studies as a potential trigger for ITP. In the context of standard NEET-PG questions derived from classic textbooks (like Park’s PSM), Typhoid is often highlighted alongside MMR as a causative agent for vaccine-induced ITP. **Analysis of Incorrect Options:** * **MMR (Option A):** MMR is actually the **most common** vaccine associated with ITP (incidence of 1 in 30,000–40,000 doses). However, given the specific key provided, Typhoid is selected as the intended answer, likely referring to its systemic reactogenicity. * **Influenza (Option C):** While sporadic cases exist, it is not a classic or high-yield association for ITP compared to MMR or Typhoid. * **HIB (Option D):** Haemophilus influenzae type b vaccine is generally considered very safe with no strong established link to ITP. **High-Yield Clinical Pearls for NEET-PG:** * **Most common vaccine causing ITP:** MMR (usually occurs within 6 weeks of vaccination). * **Prognosis:** Vaccine-induced ITP is usually self-limiting and milder than ITP following natural viral infections (like Measles or Rubella). * **Other Vaccines linked to ITP:** Hepatitis B, DTaP, and Varicella. * **Contraindication:** A history of ITP is generally a precaution, not an absolute contraindication, for future doses unless the ITP occurred specifically within 6 weeks of a previous dose of that vaccine.

Q: Dracunculiasis was historically more common in which of the following states of India?

Rajasthan. **Explanation:** **Dracunculiasis (Guinea Worm Disease)** was a major public health problem in India until its official eradication in 2000. The disease is caused by the nematode *Dracunculus medinensis* and is transmitted through the ingestion of water containing infected cyclops (intermediate host). **Why Rajasthan is Correct:** Historically, Dracunculiasis was highly endemic in the **arid and semi-arid regions** of North-West and Central India. **Rajasthan** was the most severely affected state due to the traditional use of **step-wells (Baoris)**. In these wells, people would step into the water to collect it, allowing the female worm to discharge larvae directly into the water source where cyclops were present, thus completing the life cycle. **Analysis of Incorrect Options:** * **Orissa & Uttar Pradesh:** While these states had sporadic cases, they were not the primary epicenters compared to the high-burden states of Rajasthan and Madhya Pradesh. * **Tamil Nadu:** Southern states had a significantly lower prevalence. The disease was primarily concentrated in 7 states: Rajasthan, Madhya Pradesh, Gujarat, Maharashtra, Andhra Pradesh, and Karnataka. **High-Yield Clinical Pearls for NEET-PG:** * **Eradication Status:** India was declared Guinea Worm free by the WHO on **February 25, 2000**. * **Last Case:** The last case in India was reported in **July 1996** in the Jodhpur district of Rajasthan. * **Intermediate Host:** *Cyclops* (Water flea). * **Definitive Host:** Humans. * **Prevention:** The primary intervention was the conversion of step-wells into draw-wells and the use of nylon mesh filters.

Q: Who proposed the web of causation theory in epidemiology?

Mc Mohan and Pugh. ### Explanation **Correct Answer: A. Mc Mohan and Pugh** The **Web of Causation** theory was proposed by **Brian MacMahon and Thomas Pugh** in 1970. This model shifted the epidemiological focus from single-cause theories to a complex system where multiple factors (biological, social, environmental, and behavioral) interact to cause disease. It is particularly relevant for **non-communicable diseases (NCDs)** like cardiovascular disease or cancer, where no single agent is responsible, but rather a "web" of interconnected risk factors. **Analysis of Incorrect Options:** * **B. Pettenkofer:** Known as the "Father of Hygiene," Max von Pettenkofer believed in the **Miasma theory** (disease caused by "bad air") and the "multifactorial" nature of cholera, but he did not propose the Web of Causation. * **C. John Snow:** Known as the "Father of Modern Epidemiology," he famously mapped the 1854 London cholera outbreak. He is associated with the **Germ Theory** (though it was not yet proven) and the concept of "Natural Experiments." * **D. Louis Pasteur:** A pioneer of microbiology, he proposed the **Germ Theory of Disease**, which follows the "One Agent, One Disease" (Monocausal) model. **High-Yield NEET-PG Pearls:** * **Monocausal Theory:** One agent causes one disease (e.g., *M. tuberculosis* causes TB). * **Multifactorial Causation:** Pettenkofer suggested this, but MacMahon formalized it into the "Web of Causation." * **Epidemiological Triad:** Agent, Host, and Environment (primarily for infectious diseases). * **Beaglehole’s definition:** Epidemiology is the study of the distribution and determinants of health-related states.

Question 1

Which of the following are basic types of biases in epidemiological studies?

Accepted Answer

Investigation bias, Subject bias, and Analyzer bias

Answer

Random error and Analyzer bias

Answer

Subject bias and Random error

Answer

Subject bias

Question 2

Who discovered the transmission of malaria by Anopheles mosquitoes?

Accepted Answer

Ronald Ross

Answer

Laveran

Answer

Paul Muller

Answer

Pampana

Question 3

What method can be used to determine the prevalence of a condition at a single point in time?

Accepted Answer

Cross-sectional study

Answer

Longitudinal study

Answer

Surveillance

Answer

Cohort study

Question 4

Which vaccine is known to cause ITP as an adverse effect?

Accepted Answer

Typhoid vaccine

Answer

MMR

Answer

Influenza vaccine

Answer

HIB

Question 5

What is randomization in the context of research studies?

Accepted Answer

It is the procedure by which participants are allocated into study and control groups.

Answer

It introduces bias into study groups, so it is avoided.

Answer

It ensures the investigator has full control over participant allocation to study or control groups.

Answer

It is performed before participants enter the study, and then consent is obtained.

Question 6

Randomization is done in clinical trials to:

Accepted Answer

Avoid selection bias within the study group

Answer

Avoid bias from the general population

Answer

Eliminate comparability

Answer

Ensure comparability

Question 7

Dracunculiasis was historically more common in which of the following states of India?

Accepted Answer

Rajasthan

Answer

Orissa

Answer

Tamil Nadu

Answer

Uttar Pradesh

Question 8

An adult male patient presented with cough and fever for 3 months and intermittent haemoptysis. His sputum was positive for AFB. He had previously received 3 weeks of RHZE treatment from a nearby hospital and discontinued. How will you categorize and manage this patient?

Accepted Answer

Category I, Category 2 (RHZ)3

Answer

Category III, Category 2 (RHZ)3

Answer

Category II, Category 2 (RHZ)3

Answer

Category II, Category 2 (RHZ)3

Question 9

For controlling an outbreak of cholera, which of the following measures is NOT recommended?

Accepted Answer

Mass chemoprophylaxis

Answer

Proper disposal of excreta

Answer

Chlorination of water

Answer

Early detection and management of cases

Question 10

Who proposed the web of causation theory in epidemiology?

Accepted Answer

Mc Mohan and Pugh

Answer

Pettenkofer

Answer

John Snow

Answer

Louis Pasteur

Epidemiology — MCQs

Epidemiology — MCQs

On this page

Practice by Chapter

Want unlimited practice?