Epidemiology Practice Questions

Q: Which vaccine is most sensitive to heat?

OPV. **Explanation:** The thermal stability of vaccines is a critical concept in the maintenance of the **Cold Chain**. Vaccines are biological products that lose potency when exposed to temperatures outside their recommended range. **1. Why OPV is the Correct Answer:** Oral Polio Vaccine (OPV) is the **most heat-sensitive vaccine** in the entire immunization program. It is highly thermolabile and requires storage at **-20°C** (deep freezer) for long-term potency. Even at the peripheral level (ILR), it must be kept in the coldest part of the equipment. To monitor its heat exposure, the **Vaccine Vial Monitor (VVM)** was first introduced specifically for OPV. **2. Analysis of Incorrect Options:** * **Measles (A):** While Measles is also highly heat-sensitive (especially after reconstitution), it is relatively more stable than OPV in its lyophilized (freeze-dried) form. * **DPT (C) and Hepatitis B (B):** These are **heat-stable** but **freeze-sensitive** vaccines. They lose potency if frozen (due to the aluminum adjuvant). On the heat-sensitivity spectrum, they are at the opposite end compared to OPV. **3. High-Yield Clinical Pearls for NEET-PG:** * **Order of Heat Sensitivity (Most to Least):** OPV > Measles > BCG > DPT > DT > TT > Hepatitis B. (Mnemonic: **O**nly **M**y **B**est **D**octor **T**reats **H**epatitis). * **Most Heat Resistant:** Hepatitis B (followed closely by TT). * **Freeze-Sensitive Vaccines:** All "T" series (TT, DT, DPT), Hepatitis B, and Hib. These should never be stored in the freezer. * **Shake Test:** Used to check if a freeze-sensitive vaccine (like DPT) has been damaged by sub-zero temperatures. It is **not** applicable to OPV or Measles.

Q: In a suspected TB patient, two boxes are given for sputum sample collection. They are labeled as:

a, b. **Explanation:** Under the **National Tuberculosis Elimination Program (NTEP)** guidelines (formerly RNTCP), the protocol for diagnosing pulmonary tuberculosis involves the collection of two sputum samples. According to the standardized laboratory guidelines and the **Nikshay** portal documentation, these two samples are specifically labeled as **'a'** and **'b'**. * **Sample 'a':** This is the **Spot Sample**, collected when the patient first visits the health facility. * **Sample 'b':** This is the **Morning Sample**, collected by the patient at home the following morning (which has a higher concentration of bacilli) and brought back to the facility. **Analysis of Options:** * **Option A (a, b):** This is the correct nomenclature used in the NTEP laboratory registers and on the sputum containers to maintain uniformity across the national program. * **Options B, C, and D:** While 'A/B', '1/2', or 'Y/Z' might seem like logical sequencing, they are not the official designations recognized by the program. Using non-standard labels can lead to administrative errors in the Nikshay tracking system. **High-Yield Clinical Pearls for NEET-PG:** * **Shift in Strategy:** Previously, the program required three samples. It is now **two samples** (Spot + Morning). * **Diagnostic Tool:** The preferred first investigation is now the **NAAT (CBNAAT/Truenat)** rather than traditional smear microscopy, where feasible. * **Sputum Volume:** An ideal sputum sample should be **3–5 ml** in quantity. * **Container Type:** Samples must be collected in translucent, leak-proof, wide-mouthed, sterile plastic containers.

Q: The morbidity and mortality of which of the following infections is assessed by Chandler's index?

Ancylostoma duodenale. **Explanation:** **Chandler’s Index** is a specific epidemiological tool used to measure the **average egg count per gram of feces** in a community. It is primarily used to assess the prevalence, intensity of infection, and the resulting morbidity and mortality associated with **Hookworm** (*Ancylostoma duodenale* and *Necator americanus*). 1. **Why Ancylostoma duodenale is correct:** The index provides a quantitative estimate of the worm burden. Since the severity of iron-deficiency anemia (the primary cause of morbidity in hookworm) is directly proportional to the number of adult worms in the intestine, Chandler’s Index serves as a reliable predictor of the public health impact of the disease in a specific population. * **Index 250:** High intensity (significant anemia and mortality risk). 2. **Why other options are incorrect:** * **Ascaris lumbricoides (Roundworm):** While egg counts are used to measure intensity, they are not categorized under "Chandler’s Index." * **Strongyloides & Trichuris trichiura:** These soil-transmitted helminths are measured using different quantitative techniques (like the Kato-Katz technique), but Chandler’s Index is historically and specifically synonymous with Hookworm surveys. **High-Yield Clinical Pearls for NEET-PG:** * **Hookworm & Anemia:** *Ancylostoma duodenale* causes more blood loss (~0.15–0.2 ml/day) compared to *Necator americanus* (~0.03 ml/day). * **Kato-Katz Technique:** The gold standard for field diagnosis and quantifying eggs for all soil-transmitted helminths. * **Drug of Choice:** Albendazole (400 mg single dose) is the treatment of choice for mass drug administration (MDA) programs.

Q: Which disease is transmitted by lice?

Epidemic typhus. **Explanation:** The correct answer is **Epidemic typhus**. This disease is caused by the bacterium *Rickettsia prowazekii* and is transmitted to humans by the **human body louse** (*Pediculus humanus corporis*). Transmission occurs when louse feces containing the pathogen are rubbed into bite wounds or mucous membranes. **Analysis of Options:** * **Epidemic Typhus (A):** Transmitted by **lice**. It is historically associated with overcrowded conditions, wars, and famine. A hallmark of this disease is its potential for recrudescence years later, known as **Brill-Zinsser disease**. * **Endemic Typhus / Murine Typhus (B & C):** These terms are synonymous. Both are caused by *Rickettsia typhi* and are transmitted by the **rat flea** (*Xenopsylla cheopis*). * **Rickettsial Pox (D):** Caused by *Rickettsia akari* and is transmitted by **mites** (specifically the house mouse mite, *Liponyssoides sanguineus*). **High-Yield Clinical Pearls for NEET-PG:** * **Vector Mnemonic:** Remember **"L-E"** (Lice for Epidemic) and **"F-E"** (Fleas for Endemic/Murine). * **Scrub Typhus:** Another common exam topic; it is caused by *Orientia tsutsugamushi* and transmitted by the **trombiculid mite (chigger)**. It presents with a characteristic **eschar**. * **Weil-Felix Test:** A heterophile agglutination test used for diagnosis. Note that it is **negative** in Rickettsial pox. * **Drug of Choice:** Doxycycline remains the gold standard treatment for almost all rickettsial infections.

Q: What does the case fatality rate represent?

The severity of a disease. **Explanation:** **Case Fatality Rate (CFR)** is defined as the proportion of people diagnosed with a specific disease who die from it within a specified period. It is calculated as: $$\text{CFR} = \frac{\text{Total deaths from a disease}}{\text{Total number of diagnosed cases of that disease}} \times 100$$ **Why Option A is Correct:** CFR is the primary indicator of the **virulence** or **killing power** of an infectious agent. It directly reflects the **severity of a disease** because it measures the likelihood of death once the disease is contracted. A high CFR (e.g., Rabies ~100%, Ebola ~50%) indicates a highly severe/lethal disease, whereas a low CFR (e.g., Common Cold) indicates a mild disease. **Why Other Options are Incorrect:** * **Option B (Communicability):** This refers to the ability of a disease to spread from one person to another. It is measured by the **Secondary Attack Rate (SAR)**, not CFR. * **Option C (Burden of Disease):** This represents the overall impact of a health problem in a population, including morbidity and mortality. It is typically measured using **DALYs (Disability-Adjusted Life Years)** or **Prevalence**. **High-Yield Clinical Pearls for NEET-PG:** * **CFR vs. Mortality Rate:** While CFR measures the risk of dying *among those who have the disease*, the **Cause-Specific Mortality Rate** measures the risk of dying from the disease *among the entire population*. * **Complement of CFR:** The survival rate is the complement of CFR (Survival Rate = 100 – CFR). * **Time Sensitivity:** CFR is most useful for acute infectious diseases; it is less useful for chronic diseases where the duration of illness is long. * **Rabies** has the highest CFR (nearly 100%) among infectious diseases.

Q: What is the target year for the elimination of lymphatic filariasis?

2015. **Explanation:** The correct answer is **2015**. This question refers to the specific target set by the **National Health Policy (NHP) 2002** for the elimination of Lymphatic Filariasis in India. **1. Why 2015 is Correct:** Under the National Health Policy 2002, India set a goal to eliminate Lymphatic Filariasis by 2015. In the context of Filariasis, "elimination" is defined as achieving a microfilaria rate of **less than 1%** in the community. The primary strategy used to achieve this was **Mass Drug Administration (MDA)** using a single dose of DEC (Diethylcarbamazine), later supplemented with Albendazole. **2. Analysis of Incorrect Options:** * **2010 (Option A):** This was the original global target set by the World Health Assembly in 1997, which India initially aimed for but later revised in the NHP 2002. * **2020 (Option C):** This is the **Global Target** set by the WHO (Global Programme to Eliminate Lymphatic Filariasis - GPELF). India’s national target was more ambitious than the global one. * **2012 (Option D):** This was the target year for the elimination of **Kala-azar** as per the NHP 2002 (later revised). **3. NEET-PG High-Yield Clinical Pearls:** * **Current Status:** Since the 2015 deadline was missed, the current target for Filariasis elimination in India is aligned with the global goal of **2030**, though the government recently accelerated this to **2027**. * **Drug of Choice:** DEC (6mg/kg). Note that DEC is contraindicated in **Onchocerciasis** (causes Mazzotti reaction). * **IDA Strategy:** India has introduced the **Triple Drug Therapy (IDA)**—Ivermectin, DEC, and Albendazole—in selected endemic districts to accelerate elimination. * **Vector:** *Culex quinquefasciatus* (breeds in dirty/stagnant water). * **Best time for blood collection:** 10 PM to 2 AM (due to nocturnal periodicity).

Question 1

A person is studying the relationship between deafness and mobile phone usage. Data on mobile phone usage was collected from a government source, and data on deafness was collected from district and private clinics. What type of study is this?

Accepted Answer

Ecological study

Answer

Experimental study

Answer

Etiological study

Answer

Cross-sectional study

Question 2

Which vaccine is most sensitive to heat?

Accepted Answer

OPV

Answer

Measles

Answer

Hepatitis B

Answer

DPT

Question 3

In a suspected TB patient, two boxes are given for sputum sample collection. They are labeled as:

Accepted Answer

a, b

Answer

A, B

Answer

1, 2

Answer

Y, Z

Question 4

The morbidity and mortality of which of the following infections is assessed by Chandler's index?

Accepted Answer

Ancylostoma duodenale

Answer

Ascaris lumbricoides

Answer

Strongyloides

Answer

Trichuris trichiura

Question 5

A diagnostic test has a high false positive rate in a community. What does this finding indicate?

Accepted Answer

Low prevalence

Answer

High specificity

Answer

High sensitivity

Answer

High prevalence

Question 6

Which disease is transmitted by lice?

Accepted Answer

Epidemic typhus

Answer

Endemic typhus

Answer

Murine typhus

Answer

Rickettsial pox

Question 7

Which of the following biases can be eliminated by double blinding?

Accepted Answer

Interviewer's bias

Answer

Berksonian bias

Answer

Recall bias

Answer

Selection bias

Question 8

What does the case fatality rate represent?

Accepted Answer

The severity of a disease

Answer

The communicability of a disease

Answer

The burden of a disease

Answer

None of the above

Question 9

What is the most important function of sentinel surveillance?

Accepted Answer

To find the total amount of disease in a population

Answer

To plan effective control measures

Answer

To determine the trend of disease in a population

Answer

To notify disease

Question 10

What is the target year for the elimination of lymphatic filariasis?

Accepted Answer

2015

Answer

2010

Answer

2020

Answer

2012

Epidemiology — MCQs

Epidemiology — MCQs

On this page

Practice by Chapter

Want unlimited practice?