Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 121: All of the following are zoonotic infections, except?

A. Plague
B. Japanese Encephalitis
C. HIV (Correct Answer)
D. Tuberculosis

Explanation: ### Explanation **Correct Answer: C. HIV** **Concept:** A **Zoonosis** is defined by the WHO as an infection or infectious disease transmissible under natural conditions from vertebrate animals to humans. While HIV-1 and HIV-2 originated from cross-species transmission of Simian Immunodeficiency Viruses (SIV) from primates to humans decades ago (a process called *zoonotic spillover*), HIV is now classified as a **human-only infection**. It is maintained in the population through human-to-human transmission (sexual, parenteral, or vertical) and does not require an animal reservoir for its current life cycle. **Analysis of Incorrect Options:** * **A. Plague:** A classic zoonosis caused by *Yersinia pestis*. Its natural reservoir is wild rodents (e.g., Tatera indica), and it is transmitted to humans via the bite of infected rat fleas (*Xenopsylla cheopis*). * **B. Japanese Encephalitis (JE):** An obligate zoonosis. The virus is maintained in an **Enzootic cycle** involving pigs (amplifier hosts) and water birds (ardied birds/reservoirs). Humans are "dead-end hosts." * **D. Tuberculosis:** While *M. tuberculosis* is primarily human, *Mycobacterium bovis* (Bovine TB) is a significant zoonotic pathogen transmitted to humans via unpasteurized milk or direct contact with infected cattle. Therefore, TB is traditionally included in the list of zoonotic infections. **NEET-PG High-Yield Pearls:** * **Dead-end hosts:** Humans are dead-end hosts for JE, Rabies, and Hydatid disease (transmission stops at the human). * **Cyclozoonosis:** Requires more than one vertebrate host to complete the life cycle (e.g., Echinococcosis, Taeniasis). * **Anthropozoonosis:** Infections transmitted from animals to humans (e.g., Rabies, Anthrax). * **Zooanthroponosis:** Infections transmitted from humans to animals (e.g., Human TB to cattle).

Question 122: What is the primary concern of the District TB Control Programme?

A. Finding out new cases
B. Finding out resistant cases (Correct Answer)
C. Detecting cases and ensuring treatment
D. All of the above

Explanation: **Explanation:** The primary concern of the District TB Control Programme (now integrated under the **National TB Elimination Programme - NTEP**) has evolved from simple case detection to addressing the most significant threat to TB control: **Drug Resistance**. **1. Why "Finding out resistant cases" is correct:** While the program aims to eliminate TB, the emergence of Multi-Drug Resistant (MDR-TB) and Extensively Drug-Resistant (XDR-TB) cases poses the greatest public health challenge. Resistant cases act as a reservoir for transmission of difficult-to-treat strains, leading to higher mortality and treatment failure rates. Identifying these cases early through **Universal Drug Susceptibility Testing (UDST)** is the top priority to prevent a "man-made" epidemic of incurable TB. **2. Why other options are incorrect:** * **Option A & C:** Finding new cases and ensuring treatment are fundamental *objectives* of the program. However, in the context of "primary concern" (the most critical challenge or priority), the focus shifts to the quality of the cure and preventing the spread of resistant strains. Simple case detection without addressing resistance leads to poor outcomes. * **Option D:** While all are goals, the specific "concern" or bottleneck in modern TB control is the rising trend of resistance. **High-Yield Clinical Pearls for NEET-PG:** * **NTEP Goal:** To achieve a "TB Free India" by **2025** (5 years ahead of the Global SDG target of 2030). * **UDST:** Under NTEP, every diagnosed TB patient must undergo Drug Susceptibility Testing at the time of diagnosis to rule out Rifampicin resistance. * **Diagnostic Tool of Choice:** **CBNAAT** (GeneXpert) or **Truenat** are now the preferred initial tests over sputum microscopy to identify resistance early. * **Nikshay:** The web-based portal used for monitoring TB patients and resistance patterns in India.

Question 123: Which of the following statements about chickenpox is false?

A. The causative agent is varicella-zoster virus.
B. The incubation period is typically 14-16 days.
C. The secondary attack rate is approximately 60%. (Correct Answer)
D. The rash typically spares the palms and soles.

Explanation: **Explanation:** The correct answer is **C** because the statement is factually incorrect. Chickenpox is highly contagious, and its **Secondary Attack Rate (SAR)** in household contacts is approximately **90%**, not 60%. A SAR of 90% indicates that nearly every susceptible individual in a household will contract the disease following exposure to a primary case. **Analysis of other options:** * **Option A (True):** Chickenpox is caused by the **Varicella-Zoster Virus (VZV)**, a DNA virus belonging to the Herpesviridae family (Human Herpesvirus 3). * **Option B (True):** The incubation period typically ranges from 10 to 21 days, with **14–16 days** being the most common average. * **Option D (True):** The rash of chickenpox is **centripetal** in distribution (more on the trunk, less on the limbs) and characteristically **spares the palms and soles**. This is a key clinical differentiator from Smallpox, where the rash is centrifugal and involves the palms and soles. **High-Yield Clinical Pearls for NEET-PG:** * **Period of Communicability:** From 1–2 days *before* the appearance of the rash until all lesions have crusted (usually 6 days after onset). * **Pleomorphism:** This is the hallmark of chickenpox, where all stages of the rash (papules, vesicles, and crusts) are visible simultaneously in the same area. * **Dew-drop on a rose petal:** Classic description of the clear, thin-walled vesicles. * **Congenital Varicella Syndrome:** Highest risk occurs if the mother is infected between 8–20 weeks of gestation. * **Shingles (Herpes Zoster):** Represents the reactivation of the latent VZV in the dorsal root ganglia.

Question 124: What is the best step for malaria control in an environment with high temperature?

A. Remove breeding places (Correct Answer)
B. Wear full-sleeve clothing
C. Use indoor insecticides
D. Provide early treatment

Explanation: **Explanation:** The core principle of malaria control is the **Integrated Vector Management (IVM)** strategy. In environments with **high temperatures**, the life cycle of the *Anopheles* mosquito (sporogony) is significantly accelerated, leading to rapid multiplication and higher vector density. **1. Why "Remove breeding places" is the best step:** This is a form of **Environmental Modification**, which is the most effective and permanent method of "Source Reduction." By eliminating stagnant water (breeding sites), you disrupt the mosquito life cycle at the larval stage. In high-temperature zones, where mosquitoes breed faster, preventing the birth of the vector is more sustainable and cost-effective than attempting to kill adult mosquitoes or treating an overwhelmed population. **2. Analysis of Incorrect Options:** * **B. Wear full-sleeve clothing:** This is a "Personal Prophylaxis" measure. While helpful for individual protection, it does not reduce the vector population or control the disease at a community level. * **C. Use indoor insecticides:** High temperatures can sometimes reduce the residual efficacy of certain insecticides on walls. Furthermore, chemical control is a temporary measure and is secondary to environmental management. * **D. Provide early treatment:** This is a "Secondary Prevention" measure (Early Diagnosis and Prompt Treatment - EDPT). While crucial for reducing the parasite reservoir in humans, it does not stop the transmission cycle as effectively as source reduction in a high-risk environment. **High-Yield Clinical Pearls for NEET-PG:** * **Source Reduction** is the "Permanent" method of malaria control. * **Gambusia affinis** and **Poecilia reticulata** (Guppy) are biological control agents used for larval control. * **Paris Green** is a larvicide used specifically for *Anopheles* (surface feeders). * The **extrinsic incubation period** of malaria parasites shortens as temperature increases (optimal 25-30°C), making rapid environmental intervention critical.

Question 125: What is/are true regarding the management of a rat bite?

A. Vaccinate with antirabies vaccine
B. Give tetanus toxoid
C. Rarely need rabies immunoglobulin (Correct Answer)
D. Wash with soap and use antiseptic cream

Explanation: **Explanation:** The management of rat bites is a frequent point of confusion in medical exams. The core concept to understand is that **small rodents (rats, mice, squirrels, hamsters) are not known to transmit rabies to humans.** **1. Why Option C is Correct:** According to the **WHO and National Guidelines on Rabies Prophylaxis**, small rodents are generally considered "low-risk" or "no-risk" for rabies. While they can theoretically be infected, they usually die from the predator's bite before they can transmit the virus. Therefore, **Post-Exposure Prophylaxis (PEP), including Rabies Immunoglobulin (RIG) and the Rabies Vaccine, is not routinely recommended** for rat bites. RIG is "rarely" needed unless the animal was confirmed to be rabid or showed highly unusual behavior in an endemic area. **2. Why Other Options are Incorrect:** * **Option A:** Routine vaccination with ARV is not indicated for rat bites for the reasons mentioned above. * **Option B:** While Tetanus Toxoid (TT) is part of general wound management, it is not the *defining* or most specific management priority unique to the clinical dilemma of "rabies vs. no rabies" in rat bites. * **Option D:** Washing with soap and water is standard for any wound, but in the context of this specific question, the examiner is testing your knowledge of rabies protocol. **High-Yield Clinical Pearls for NEET-PG:** * **Rat-Bite Fever:** The primary concern in rat bites is not rabies, but infections caused by *Streptobacillus moniliformis* or *Spirillum minus*. * **Rabies-Free Animals:** Bites from rabbits, hares, and small rodents do **not** require rabies PEP. * **Treatment of Choice:** For Rat-Bite Fever, the drug of choice is **Penicillin G**. * **Category III Bites:** For high-risk animals (dogs, cats, monkeys), RIG is mandatory for all Category III exposures. For rats, it is omitted.

Question 126: Which of the following has the least chance of transmitting HIV infection?

A. Heterosexual intercourse (Correct Answer)
B. Blood transfusion
C. Vertical transmission
D. IV drug abuse

Explanation: ### Explanation The risk of HIV transmission varies significantly depending on the route of exposure and the viral load of the source. This question asks for the **least** efficient mode of transmission among the given options. **1. Why Heterosexual Intercourse is the Correct Answer:** While heterosexual intercourse is the most common mode of transmission globally due to the sheer frequency of the act, it has the **lowest per-act risk** (approximately 0.04% to 0.1% for females and 0.04% for males). The low efficiency is due to the mucosal barrier and the relatively low concentration of the virus in vaginal or seminal fluids compared to whole blood. **2. Analysis of Incorrect Options:** * **Blood Transfusion:** This is the **most efficient** mode of transmission. A single unit of HIV-infected blood carries a transmission risk of approximately **90-95%**. * **Vertical Transmission:** Without intervention, the risk of mother-to-child transmission (MTCT) is about **20-45%**. With modern ART and PMTCT protocols, this can be reduced to <1%. * **IV Drug Abuse:** Sharing needles involves direct vascular access with contaminated blood. The per-act risk is approximately **0.63% to 0.8%**, which is significantly higher than a single act of heterosexual intercourse. **3. NEET-PG High-Yield Pearls:** * **Efficiency Order:** Blood Transfusion (90%) > Vertical (30%) > Needle prick (0.3%) > Receptive Anal Sex (1.38%) > Receptive Vaginal Sex (0.08%). * **Most Common Route:** Globally and in India, **Heterosexual transmission** is the most common route. * **Window Period:** Usually 2–12 weeks; the best screening test is **4th Gen ELISA** (detects p24 antigen + antibodies). * **Post-Exposure Prophylaxis (PEP):** Must be started within **72 hours** (ideally within 2 hours) and continued for **28 days**.

Question 127: Which of the following is excluded from the National Vector Borne Disease Control Programme (NVBDCP)?

A. Malaria
B. Filariasis
C. Kala-azar
D. Kyasanur Forest Disease (KFD) (Correct Answer)

Explanation: **Explanation:** The **National Vector Borne Disease Control Programme (NVBDCP)**, now subsumed under the National Center for Vector Borne Diseases Control (NCVBDC), is an umbrella programme in India targeting specific vector-borne diseases of public health importance. **Why Kyasanur Forest Disease (KFD) is the correct answer:** KFD, also known as "Monkey Fever," is a tick-borne viral hemorrhagic fever primarily localized to specific districts in Karnataka and neighboring states. While it is a vector-borne disease, it is **not** included under the NVBDCP. It is instead monitored under the Integrated Disease Surveillance Programme (IDSP) due to its localized geographical distribution. **Analysis of Incorrect Options:** The NVBDCP currently covers **six** specific diseases: * **A. Malaria:** Transmitted by the *Anopheles* mosquito; it is the primary focus of the programme. * **B. Filariasis:** Transmitted by *Culex* mosquitoes; the programme aims for elimination through Mass Drug Administration (MDA). * **C. Kala-azar (Visceral Leishmaniasis):** Transmitted by the Sandfly (*Phlebotomus argentipes*); targeted for elimination in endemic states (Bihar, Jharkhand, UP, West Bengal). * *Note: The remaining three diseases under NVBDCP are **Dengue, Chikungunya, and Japanese Encephalitis.*** **High-Yield Clinical Pearls for NEET-PG:** * **The "Big 6":** Remember the mnemonic **"MD-KFC-J"** (Malaria, Dengue, Kala-azar, Filariasis, Chikungunya, Japanese Encephalitis). * **Elimination Targets:** India aims to eliminate Malaria by 2030 and Lymphatic Filariasis/Kala-azar in the near future. * **KFD Vector:** The principal vector for KFD is the hard tick (*Haemaphysalis spinigera*). * **KFD Vaccine:** Unlike most NVBDCP diseases, a formal killed vaccine exists for KFD (though its efficacy is debated).

Question 128: Under the Enhanced Malaria Control Programme (EMCP) launched in 1997, which of the following was NOT a criterion for the selection of Primary Health Centres (PHCs)?

A. API greater than 2 for the last 3 years
B. Plasmodium falciparum comprising more than 30% of total malaria cases
C. The area has been reporting deaths
D. The area has been reporting epidemics (Correct Answer)

Explanation: ### Explanation The **Enhanced Malaria Control Project (EMCP)** was launched in 1997 with support from the World Bank to intensify malaria control in high-burden areas. The selection of Primary Health Centres (PHCs) for this program was based on specific epidemiological criteria aimed at targeting endemicity rather than sporadic outbreaks. **Why Option D is the Correct Answer:** Reporting **epidemics** was **NOT** a criterion for selection under EMCP. The program focused on areas with stable, high-intensity transmission (endemicity) rather than unstable areas prone to sudden epidemics. Epidemic-prone areas were managed under different surveillance protocols of the National Anti-Malaria Programme (NAMP). **Analysis of Incorrect Options (Criteria for EMCP):** * **Option A (API > 2):** An Annual Parasite Incidence (API) of more than 2 for the previous three years was a primary criterion, indicating a sustained high burden of disease. * **Option B (Pf % > 30%):** Areas where *Plasmodium falciparum* accounted for more than 30% of total cases were prioritized due to the higher risk of severe malaria and drug resistance. * **Option C (Reporting Deaths):** Any area reporting deaths due to malaria was automatically considered high-risk and included to reduce mortality. * *Note: Additional criteria included areas with a high proportion of tribal populations.* ### High-Yield Clinical Pearls for NEET-PG * **EMCP Timeline:** Launched in 1997; later integrated into the **National Vector Borne Disease Control Programme (NVBDCP)** in 2003-04. * **API Formula:** (Total confirmed cases in a year / Total population under surveillance) × 1000. * **ABER (Annual Blood Examination Rate):** A key indicator of surveillance quality; it should ideally be **>10%**. * **Current Strategy:** India is currently following the **National Framework for Malaria Elimination (2016-2030)**, aiming for a malaria-free India by 2030.

Question 129: What is the minimum period required for post-exposure chemoprophylaxis for HIV?

A. 4 weeks (Correct Answer)
B. 6 weeks
C. 8 weeks
D. 12 weeks

Explanation: **Explanation:** The correct answer is **4 weeks (28 days)**. Post-exposure prophylaxis (PEP) for HIV is a medical emergency aimed at preventing viral replication and systemic dissemination following potential exposure (e.g., needle-stick injury or sexual assault). **Why 4 weeks is correct:** According to the National AIDS Control Organization (NACO) and WHO guidelines, the standard duration for PEP is **28 days**. This timeframe is based on the biological rationale that it takes approximately 4 weeks of continuous antiretroviral therapy to effectively inhibit the virus from establishing a permanent infection in the host's lymphoid tissues after the initial inoculation. **Analysis of Incorrect Options:** * **6 weeks & 8 weeks:** These durations are unnecessarily long. Extending the regimen beyond 28 days does not provide additional protection but significantly increases the risk of drug toxicity and poor patient compliance. * **12 weeks:** This is often the timeframe used for **follow-up antibody testing** to confirm seroconversion status, but it is not the duration for medication intake. **High-Yield Clinical Pearls for NEET-PG:** * **The "Golden Period":** PEP should ideally be started within **2 hours**, and no later than **72 hours** post-exposure. It is not recommended after 72 hours. * **Preferred Regimen (NACO):** A 3-drug regimen is now standard, typically consisting of **Tenofovir (300mg) + Lamivudine (300mg) + Dolutegravir (50mg)** as a once-daily fixed-dose combination. * **Follow-up Schedule:** Testing for HIV antibodies should be done at baseline, 6 weeks, and 3 months (12 weeks) post-exposure.

Question 130: When planning home care for a client with hepatitis A, which preventive measure should be emphasized to protect the client’s family?

A. Keeping the client in complete isolation
B. Using good sanitation with dishes and shared bathrooms (Correct Answer)
C. Avoiding contact with blood-soiled clothing or dressings
D. Forbidding the sharing of needles or syringes

Explanation: **Explanation:** **1. Why Option B is Correct:** Hepatitis A Virus (HAV) is primarily transmitted via the **fecal-oral route**. In a home setting, the virus is shed in the feces of the infected individual. Transmission occurs through contaminated food, water, or fomites (shared objects). Therefore, the cornerstone of prevention is breaking the chain of transmission through **stringent personal hygiene and sanitation**. This includes meticulous handwashing, disinfecting shared bathrooms, and ensuring dishes are thoroughly cleaned to prevent cross-contamination among family members. **2. Why Other Options are Incorrect:** * **Option A:** Complete isolation is unnecessary. Standard enteric precautions are sufficient. Once jaundice appears, the period of peak infectivity has usually passed. * **Option C & D:** These measures are specific to **Hepatitis B, C, and D**, which are transmitted via parenteral (blood-borne) and sexual routes. While general hygiene is good practice, HAV is not typically spread through blood or needle sharing. **3. NEET-PG High-Yield Pearls:** * **Incubation Period:** 15–45 days (Average: 28 days). * **Infectivity:** Maximum during the late incubation period (2 weeks before the onset of jaundice) and decreases rapidly after jaundice appears. * **Diagnosis:** **Anti-HAV IgM** is the gold standard for acute infection; **Anti-HAV IgG** indicates past infection or immunity. * **Prophylaxis:** * **Active:** Inactivated HAV vaccine (2 doses, 6–12 months apart). * **Passive:** Immunoglobulin (0.02 mL/kg) given within 2 weeks of exposure. * **Complication:** HAV never leads to chronic hepatitis or a carrier state, unlike HBV or HCV. It can, however, rarely cause Fulminant Hepatic Failure.

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Communicable Disease Control Principles

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Water-Borne Diseases

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Air-Borne Diseases

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HIV/AIDS Control Program

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Tuberculosis Control

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Leprosy Elimination

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Emerging and Re-emerging Infections

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Hospital-Acquired Infections

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Integrated Disease Surveillance Project

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