Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 31: Presence of an infectious agent on clothes or dressings is termed?

A. Infection
B. Infestation
C. Contamination (Correct Answer)
D. Contagion

Explanation: **Explanation:** The presence of an infectious agent on the surface of a body, or on inanimate objects like clothes, dressings, water, or food, is termed **Contamination**. 1. **Why Contamination is Correct:** Contamination refers to the mere presence of pathogens on an external surface (fomites or skin) without the agent necessarily entering the tissues or multiplying. In this case, clothes and dressings act as **fomites**, serving as vehicles for potential transmission. 2. **Why the other options are incorrect:** * **Infection:** This is the entry, development, and multiplication of an infectious agent in the body of a human or animal. Unlike contamination, infection implies a biological interaction with the host's tissues. * **Infestation:** This term is specifically used for the lodgment, development, and reproduction of **arthropods** (e.g., lice, mites, ticks) on the surface of the body or in clothing (e.g., Pediculosis, Scabies). * **Contagion:** This is an older, less technical term referring to the transmission of disease by direct or indirect contact. It does not specifically define the presence of an agent on an object. **High-Yield Clinical Pearls for NEET-PG:** * **Pollution:** The presence of offensive but not necessarily infectious matter in the environment (e.g., chemicals in water). * **Host Defenses:** Contamination does not always lead to infection; the "Infectious Dose" and host immunity determine if the agent will successfully invade. * **Fomites:** Inanimate objects (like the clothes/dressings mentioned) that can transfer pathogens are classic examples of indirect transmission. * **Ectoparasites:** Always associate "Infestation" with ectoparasites like *Sarcoptes scabiei*.

Question 32: Which of the following definitions corresponds to a generalized HIV epidemic?

A. Prevalence in pregnant women greater than 0.5%
B. Prevalence in a population greater than 0.5%
C. Prevalence in pregnant women greater than 1% (Correct Answer)
D. Prevalence in a population greater than 1%

Explanation: ### Explanation The classification of HIV epidemics is based on the prevalence of the infection within specific subgroups, as defined by **WHO and UNAIDS**. This categorization helps public health officials determine the intensity of the epidemic and the necessary scale of intervention. **1. Why Option C is Correct:** A **Generalized Epidemic** is defined as an epidemic where HIV is firmly established in the general population. The technical threshold for this is a **prevalence of >1% in pregnant women** attending antenatal clinics (ANC). Pregnant women are used as a proxy for the general sexually active population because they are easily accessible for screening and represent heterosexual transmission patterns. In this stage, sexual networking in the general population is sufficient to sustain the epidemic independent of sub-populations at higher risk. **2. Analysis of Incorrect Options:** * **Options A & B:** The 0.5% threshold is not a standard WHO/UNAIDS metric for defining epidemic states. * **Option D:** While a prevalence of >1% in the "general population" is conceptually similar, the specific epidemiological indicator used for global monitoring and classification is specifically **pregnant women** (ANC data). **3. High-Yield Clinical Pearls for NEET-PG:** * **Low-level Epidemic:** HIV prevalence has not consistently exceeded 5% in any defined sub-population (e.g., FSW, MSM, IDU). * **Concentrated Epidemic:** HIV prevalence is consistently **>5% in at least one defined high-risk sub-population** (e.g., FSW, IDU, MSM) but remains **<1% in pregnant women** in urban areas. * **Sentinel Surveillance:** In India, the National AIDS Control Organisation (NACO) uses sentinel surveillance sites to monitor these trends, primarily focusing on ANC attendees and High-Risk Groups (HRGs).

Question 33: Following bleeding from a wound after a dog bite, what is the recommended treatment?

A. Wound cleansing only
B. Antirabies vaccine only
C. Antirabies vaccine and wound cleansing
D. Wound cleansing, antirabies vaccine, and rabies immunoglobulin (Correct Answer)

Explanation: ### Explanation The management of a dog bite depends on the **WHO Category of Exposure**. The question describes a wound with **bleeding**, which classifies it as a **Category III exposure** (transdermal bites or scratches, licks on broken skin, or contamination of mucous membranes with saliva). **Why Option D is Correct:** According to the WHO and National Guidelines for Rabies Prophylaxis, Category III exposures require a three-pronged approach: 1. **Wound Cleansing:** Immediate flushing of the wound with soap and running water for at least 15 minutes to mechanically remove the virus. 2. **Anti-Rabies Vaccine (ARV):** To stimulate active immunity. 3. **Rabies Immunoglobulin (RIG):** To provide immediate passive immunity by neutralizing the virus at the site before the vaccine-induced antibodies develop (which takes about 7–14 days). **Why Other Options are Incorrect:** * **Option A & B:** These are incomplete treatments. Relying solely on cleansing or vaccination in a Category III bite carries a high risk of treatment failure, as the virus may reach the peripheral nerves before active immunity is established. * **Option C:** This is the protocol for **Category II** exposure (minor scratches without bleeding). Since bleeding is present, RIG is mandatory. **High-Yield Clinical Pearls for NEET-PG:** * **Wound Care:** Avoid suturing rabies-prone wounds. If suturing is unavoidable, it should be done 24–48 hours later under the cover of RIG. * **RIG Administration:** The entire calculated dose of RIG should be infiltrated **into and around the wound**. Any remainder should be injected IM at a site distant from the vaccine. * **Vaccination Schedules:** * **Intramuscular (Essen):** 0, 3, 7, 14, 28 days. * **Intradermal (Updated Thai Red Cross):** 0, 3, 7, 28 days (2-2-2-0-2 regimen). * **Re-exposure:** If a previously immunized person is bitten, only two booster doses of ARV (Days 0 and 3) are needed; **RIG is not required.**

Question 34: "Nikshay" is a central government software used for tracking which of the following?

A. Tuberculosis (Correct Answer)
B. High-risk pregnancies
C. High-risk newborns
D. Malaria

Explanation: **Explanation:** **Nikshay** is the web-based surveillance and case management system for the **National Tuberculosis Elimination Program (NTEP)** in India. The name is derived from "Ni" (End) and "Kshay" (Tuberculosis). It serves as a unified ICT platform for monitoring TB patients, notification by private and public providers, and managing treatment adherence. * **Why Tuberculosis is Correct:** Nikshay is the backbone of TB surveillance in India. It facilitates the **Direct Benefit Transfer (DBT)** under the *Nikshay Poshan Yojana*, providing ₹500/month for nutritional support to TB patients. It also tracks drug-resistant TB (DR-TB) and ensures real-time reporting, which is crucial for the goal of eliminating TB by 2025. * **Why Other Options are Incorrect:** * **High-risk pregnancies & High-risk newborns:** These are tracked via the **RCH (Reproductive and Child Health) portal** or the **ANMOL** (ANM Online) app. The **Kilkari** service is also used for providing health messages to pregnant women and mothers. * **Malaria:** Surveillance for Malaria and other vector-borne diseases is primarily integrated into the **IHIP (Integrated Health Information Platform)** and the National Center for Vector Borne Diseases Control (NCVBDC) reporting systems. **High-Yield Clinical Pearls for NEET-PG:** * **Nikshay Poshan Yojana:** Financial incentive for TB patients (₹500/month). * **Nikshay Mitra:** A component of the *Pradhan Mantri TB Mukt Bharat Abhiyaan* where individuals/organizations can "adopt" TB patients to provide nutritional and vocational support. * **Notification:** TB is a **notifiable disease** in India since 2012; failure to notify via Nikshay can lead to legal action under Section 269/270 of the IPC.

Question 35: What is the incubation period of pertussis?

A. 7 days
B. 7-14 days (Correct Answer)
C. 14-28 days
D. 28 days

Explanation: **Explanation:** **Pertussis (Whooping Cough)** is a highly contagious respiratory infection caused by the bacterium *Bordetella pertussis*. **1. Why Option B is Correct:** The incubation period (IP) for pertussis is typically **7 to 14 days**, with an upper limit of 21 days. During this period, the bacteria colonize the ciliated epithelium of the respiratory tract, but the patient remains asymptomatic. Understanding this timeframe is crucial for post-exposure prophylaxis and determining the period of surveillance for contacts. **2. Why Other Options are Incorrect:** * **Option A (7 days):** While the IP can be as short as 7 days, this option represents only the lower limit and does not cover the standard clinical range. * **Option C & D (14-28 days / 28 days):** These are too long. An IP exceeding 21 days is rare for pertussis. Such long durations are more characteristic of diseases like Typhoid (10-14 days) or Hepatitis A (15-45 days). **3. High-Yield Clinical Pearls for NEET-PG:** * **Infectivity:** The patient is most infectious during the **catarrhal stage** (the first 1-2 weeks), which mimics a common cold. * **Secondary Attack Rate:** Very high, approximately **80-90%** among susceptible household contacts. * **Drug of Choice:** **Erythromycin** (or other Macrolides like Azithromycin) is the treatment of choice. It reduces communicability but is most effective if started in the catarrhal stage. * **Vaccination:** Part of the National Immunization Schedule (Pentavalent/DPT). The "acellular" vaccine (aP) has fewer side effects than the "whole-cell" (wP) vaccine. * **Diagnosis:** **Nasopharyngeal swab** is the gold standard; culture is done on **Regan-Lowe** or **Bordet-Gengou medium**.

Question 36: Which of the following influenza strains led to an outbreak in China in 2013?

A. H7N9 (Correct Answer)
B. H3N2
C. H1N1
D. H2N2

Explanation: **Explanation:** The correct answer is **H7N9**. In March 2013, the World Health Organization (WHO) reported the first human infections with a novel **Avian Influenza A (H7N9)** virus in Eastern China. This outbreak was significant because it marked the first time this specific low-pathogenic avian virus crossed the species barrier to infect humans, causing severe pneumonia and high mortality rates. **Analysis of Options:** * **H3N2 (Option B):** This strain was responsible for the **"Hong Kong Flu" pandemic of 1968**. It remains a common cause of seasonal influenza today but was not the novel strain of the 2013 China outbreak. * **H1N1 (Option C):** This strain caused the **"Spanish Flu" (1918)** and the **"Swine Flu" pandemic (2009)**. While H1N1 is endemic globally, it was not the specific emerging strain identified in the 2013 avian outbreak. * **H2N2 (Option D):** This strain caused the **"Asian Flu" pandemic of 1957**. It disappeared from human circulation around 1968, replaced by H3N2. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Shift vs. Drift:** Shift (major change/reassortment) leads to **Pandemics**; Drift (minor point mutations) leads to **Epidemics**. * **H5N1:** Known as "Bird Flu," first human outbreak occurred in Hong Kong (1997). * **Drug of Choice:** Oseltamivir (Neuraminidase inhibitor) is the standard treatment for severe influenza strains, including H7N9. * **Reservoir:** Wild aquatic birds are the natural reservoirs for all Influenza A viruses.

Question 37: What is the standard dose of Tuberculin used in the Mantoux test?

A. 1 TU in 1 ml
B. 1 TU in 0.1 ml (Correct Answer)
C. 0.1 TU in 1 ml
D. 0.1 TU in 0.1 ml

Explanation: ### Explanation **1. Understanding the Correct Answer (B):** The Mantoux test (Tuberculin Skin Test) is the standard method for identifying latent *Mycobacterium tuberculosis* infection. The standard dose recommended by the WHO and used in India (RNTCP/NTEP guidelines) is **1 TU (Tuberculin Unit) of PPD RT23**. This dose is contained in a volume of **0.1 ml**, which is injected **intradermally** on the volar aspect of the forearm using a tuberculin syringe. This specific volume is chosen because it creates a discrete 6–10 mm wheal, allowing for the standardized delivery of the antigen to the dermis. **2. Analysis of Incorrect Options:** * **Option A (1 TU in 1 ml):** This is incorrect because 1 ml is a very large volume for an intradermal injection; it would cause significant tissue trauma and would not allow for the localized delayed-type hypersensitivity reaction required for the test. * **Option C (0.1 TU in 1 ml):** This is incorrect as the dosage is too low (sub-therapeutic for a reaction) and the volume is too high. * **Option D (0.1 TU in 0.1 ml):** While the volume is correct, the concentration is insufficient. 0.1 TU is not potent enough to elicit a reliable diagnostic response in most individuals. **3. High-Yield Clinical Pearls for NEET-PG:** * **Standard Antigen:** PPD RT23 with Tween 80 (stabilizer) is most commonly used. * **Reading the Test:** Results must be read **48 to 72 hours** after injection. * **Measurement:** Only the **induration** (palpable hardening) is measured, not the erythema (redness). * **Interpretation:** In India, an induration of **≥10 mm** is generally considered positive. In HIV-positive individuals, **≥5 mm** is considered positive. * **False Negative:** Can occur in miliary TB, malnutrition, sarcoidosis, or recent viral infections (e.g., Measles). * **False Positive:** Can occur due to prior BCG vaccination or infection with Non-Tuberculous Mycobacteria (NTM).

Question 38: The SAPEL initiative is associated with which disease?

A. Smallpox
B. Plague
C. Leprosy (Correct Answer)
D. Malaria

Explanation: **Explanation:** The **SAPEL** initiative stands for **Special Action Projects for the Elimination of Leprosy**. It was launched by the World Health Organization (WHO) to address a specific challenge in leprosy control: reaching underserved and marginalized populations living in remote or inaccessible areas where routine Multi-Drug Therapy (MDT) services are difficult to implement. **Why Leprosy is correct:** SAPEL focuses on "equity" in healthcare. It targets pockets of high endemicity or geographically isolated communities (e.g., hilly terrains, deep forests, or nomadic groups) to ensure that no leprosy case remains untreated, thereby breaking the chain of transmission and preventing disability. **Why other options are incorrect:** * **Smallpox:** Associated with the "Global Smallpox Eradication Programme" and the "Target Zero" strategy. It was declared eradicated in 1980. * **Plague:** Managed under the International Health Regulations (IHR). Control focuses on flea control (insecticides) and rodent management, not SAPEL. * **Malaria:** Associated with initiatives like "Roll Back Malaria," "MACEPA," and the "High Burden to High Impact" (HBHI) strategy. **High-Yield NEET-PG Pearls for Leprosy:** * **LEC (Leprosy Elimination Campaigns):** Short-term intensive activities to detect hidden cases in the community. * **MDDT (Accompanied MDT):** Providing a patient with the full course of treatment at once if frequent clinic visits are impossible. * **Milestone:** India achieved the goal of "Elimination of Leprosy as a Public Health Problem" (defined as <1 case per 10,000 population) at the national level in December 2005. * **Current Strategy:** The National Strategic Plan (2023-2027) aims for **"Mukti"** (Zero Transmission) by 2027.

Question 39: In which year did the WHO declare that smallpox has been eradicated?

A. 1992
B. 2000
C. 1980 (Correct Answer)
D. 1985

Explanation: **Explanation:** Smallpox (caused by the Variola virus) holds the distinction of being the first human infectious disease to be eradicated globally. The correct answer is **1980**, as the 33rd World Health Assembly officially declared the world free of smallpox on **May 8, 1980**, following the success of the Intensified Smallpox Eradication Programme. **Analysis of Options:** * **1980 (Correct):** This marks the official WHO certification of global eradication. The last naturally occurring case of *Variola major* was recorded in Bangladesh (1975), and the last case of *Variola minor* was in Somalia (1977). * **1992:** This year is irrelevant to smallpox; however, in India, 1992 marked the launch of the Child Survival and Safe Motherhood (CSSM) programme. * **2000:** While a popular target year for many "Health for All" goals, it does not correlate with smallpox eradication. * **1985:** This year is significant for the launch of the Universal Immunization Programme (UIP) in India, but not for smallpox. **High-Yield Clinical Pearls for NEET-PG:** * **Last Case in India:** May 24, 1975 (Bhanu Bibi, Bihar). * **India Declared Smallpox Free:** April 1977. * **Last Case in the World (Natural):** Ali Maow Maalin (Somalia, 1977). * **Last Case Overall (Laboratory Accident):** Janet Parker (UK, 1978). * **Vaccine:** Developed by **Edward Jenner** (1796), it was a live vaccine using the Vaccinia virus. * **Key Strategy:** The "Search and Surveillance" strategy and "Ring Vaccination" were pivotal in its eradication.

Question 40: Which test is done for tuberculosis screening?

A. Sputum microscopy
B. Sputum culture
C. Tuberculin test (Correct Answer)
D. Lymph node biopsy

Explanation: **Explanation:** The correct answer is **C. Tuberculin test (Mantoux test)**. In epidemiology and community medicine, a **screening test** is used to identify asymptomatic individuals who may have a disease or infection within a large population. The Tuberculin Skin Test (TST) measures the delayed-type hypersensitivity reaction to Purified Protein Derivative (PPD). It is the standard tool for screening because it identifies "latent tuberculosis infection" (LTBI), even when no clinical disease is present. **Analysis of Incorrect Options:** * **A. Sputum microscopy:** This is a **diagnostic test** used to confirm active pulmonary tuberculosis in symptomatic patients (Presumptive TB). It is the primary tool for the National TB Elimination Program (NTEP) but is not used for screening the general asymptomatic population. * **B. Sputum culture:** This is the **"Gold Standard" for diagnosis**. It is highly specific and sensitive but takes 2–8 weeks for results, making it impractical for mass screening. * **C. Lymph node biopsy:** This is a diagnostic procedure used specifically for **Extrapulmonary TB** (Tubercular Lymphadenitis) to look for caseating granulomas. **High-Yield Clinical Pearls for NEET-PG:** * **Interpretation:** An induration of **≥10 mm** after 48–72 hours is generally considered positive in India. * **BCG Effect:** A prior BCG vaccination can cause a false-positive TST, though the reaction usually diminishes over time. * **Anergy:** False negatives can occur in immunocompromised states (HIV, malnutrition, miliary TB, or recent viral infections like Measles). * **IGRA:** Interferon-Gamma Release Assays (like QuantiFERON-TB Gold) are newer screening alternatives that do not cross-react with the BCG vaccine.

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