Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 131: What is the risk of mother-to-child HIV transmission during delivery and after delivery in a non-breastfeeding woman?

A. 5-10%
B. 15-30% (Correct Answer)
C. 10-15%
D. More than 50%

Explanation: ### Explanation **1. Why Option B (15-30%) is Correct:** In the absence of any medical intervention (Antiretroviral Therapy or ART), the risk of Mother-to-Child Transmission (MTCT) of HIV is approximately **15-30%** in non-breastfeeding women. This transmission occurs primarily during two phases: **In-utero** (5-10%) and **Intrapartum/During delivery** (10-20%). The intrapartum period carries a higher risk due to the infant's exposure to infected maternal blood and vaginal secretions during labor. **2. Analysis of Incorrect Options:** * **Option A (5-10%):** This represents the risk of transmission specifically during the *antenatal* period (in-utero) only. It does not account for the significant risk during delivery. * **Option C (10-15%):** This is the additional risk attributed specifically to *breastfeeding* if the mother continues it for up to 24 months. If a woman breastfeeds, the total cumulative risk rises from 15-30% to approximately 35-45%. * **Option D (>50%):** This is incorrectly high. Even without intervention, more than half of the children born to HIV-positive mothers will not contract the virus. **3. High-Yield Clinical Pearls for NEET-PG:** * **Total Risk (No Intervention):** 15-30% (Non-breastfeeding) vs. 35-45% (Breastfeeding). * **Impact of ART:** With effective ART and undetectable viral load, the risk of MTCT can be reduced to **less than 1%**. * **PPTCT Protocol (India):** All pregnant women are screened for HIV. If positive, the mother is started on a lifelong **TLD regimen** (Tenofovir + Lamivudine + Dolutegravir) regardless of CD4 count. * **Infant Prophylaxis:** Nevirapine syrup is given to the infant for 6 weeks (can be extended to 12 weeks in high-risk cases). * **Diagnosis in Infants:** HIV DNA PCR is the gold standard (at 6 weeks); antibody tests (ELISA) are unreliable before 18 months due to persisting maternal antibodies.

Question 132: Which of the following is NOT transmitted by soft ticks?

A. Kyasanur Forest Disease (KFD)
B. Tularemia (Correct Answer)
C. Q fever
D. Relapsing fever

Explanation: **Explanation:** The core concept here is distinguishing between diseases transmitted by **Hard Ticks (Ixodidae)** versus **Soft Ticks (Argasidae)**. **Why Tularemia is the correct answer:** Tularemia (caused by *Francisella tularensis*) is primarily transmitted by **Hard Ticks** (such as *Dermacentor* and *Amblyomma* species), biting flies, or direct contact with infected animals like rabbits. It is **not** transmitted by soft ticks. **Analysis of other options:** * **Relapsing Fever (Endemic):** This is the classic disease associated with **Soft Ticks** (specifically the *Ornithodoros* genus). It is caused by *Borrelia* species. * **Kyasanur Forest Disease (KFD):** While KFD is primarily transmitted by Hard Ticks (*Haemaphysalis spinigera*), the question asks which is *not* transmitted by soft ticks. In complex entomology, some sources note rare soft tick associations, but more importantly, **Q Fever** and **Tularemia** are the primary distractors here. * **Q Fever:** Caused by *Coxiella burnetii*, it is primarily an airborne infection (inhalation of dust), but it can be transmitted by **both** hard and soft ticks in sylvatic cycles. **Note on Question Ambiguity:** In many standard textbooks, KFD and Tularemia are strictly Hard Tick-borne. However, in the context of NEET-PG, Tularemia is frequently categorized under Hard Ticks/Flies, while Relapsing Fever is the "gold standard" for Soft Tick transmission. **High-Yield Clinical Pearls for NEET-PG:** * **Soft Ticks (Argasidae):** Remember the mnemonic **"L-O-R"** — **L**ouse-borne relapsing fever (Lice), **O**rnithodoros (Soft Tick), **R**elapsing fever (Endemic). * **Hard Ticks (Ixodidae):** Transmit KFD, Indian Tick Typhus, Tularemia, Rocky Mountain Spotted Fever, and Babesiosis. * **KFD (Monkey Fever):** High-yield for India; vector is *Haemaphysalis spinigera*; reservoir is monkeys/rodents. * **Q Fever:** Most common route is **inhalation** (not tick bite), often associated with livestock/parturition products.

Question 133: What is the best method for immunoprophylaxis of leprosy?

A. MMR vaccine
B. Killed ICRC bacillus (Correct Answer)
C. Plague bacillus vaccine
D. Anthrax bacillus vaccine

Explanation: **Explanation:** The immunoprophylaxis of Leprosy involves the use of specific mycobacterial vaccines to stimulate cell-mediated immunity (CMI) against *Mycobacterium leprae*. **Why Killed ICRC Bacillus is Correct:** The **ICRC vaccine** (Indian Cancer Research Centre) is a first-generation vaccine derived from a cultivable mycobacterium belonging to the *M. avium-intracellulare* group, isolated from human lepromata. It shares significant antigenic determinants with *M. leprae*. Clinical trials in India have demonstrated that it provides significant protection and induces lepromin conversion in lepromatous leprosy patients and their contacts. Other vaccines used in leprosy include the **Mycobacterium w (Mw)** vaccine (now known as Leprovac) and the BCG vaccine (which offers variable protection). **Analysis of Incorrect Options:** * **A. MMR vaccine:** This is a live attenuated vaccine used for Measles, Mumps, and Rubella. It has no antigenic similarity to mycobacteria and provides no protection against leprosy. * **C. Plague bacillus vaccine:** This is used for *Yersinia pestis*. It is a killed vaccine (though newer versions exist) and is unrelated to leprosy prophylaxis. * **D. Anthrax bacillus vaccine:** This is used for *Bacillus anthracis*, primarily for high-risk individuals (veterinarians/military). It has no role in mycobacterial immunity. **High-Yield Pearls for NEET-PG:** * **BCG Vaccine:** While primarily for TB, BCG offers 20-40% protection against leprosy. Adding killed *M. leprae* to BCG increases its efficacy. * **Mycobacterium w (Mw):** Developed in India by Dr. G.P. Talwar; it is used as an immunotherapeutic adjunct to MDT. * **Chemoprophylaxis:** The current WHO recommendation for contacts of leprosy patients is a **Single Dose of Rifampicin (SDR)**. * **Most common site of leprosy:** Skin and peripheral nerves.

Question 134: Which marker(s) indicate(s) acute Hepatitis B infection?

A. HBsAg
B. HBeAg (Correct Answer)
C. Anti HBc
D. Anti HBs

Explanation: In Hepatitis B serology, understanding the timeline of markers is crucial for NEET-PG. **Why HBeAg is the correct answer:** **HBeAg (Hepatitis B e-Antigen)** is a marker of **active viral replication** and high infectivity. It appears shortly after HBsAg during the early phase of acute infection. Its presence signifies that the virus is actively multiplying, making it a hallmark of the **acute stage** and a key indicator of a patient's ability to transmit the virus. **Analysis of Incorrect Options:** * **HBsAg (Hepatitis B Surface Antigen):** While it is the first marker to appear in acute infection, its presence alone does not distinguish between acute and chronic states (as it persists beyond 6 months in chronic cases). * **Anti-HBc (Antibody to Core Antigen):** This is a "bridge" marker. **IgM anti-HBc** is the specific marker for acute infection (and is the only marker present during the 'window period'), whereas **IgG anti-HBc** indicates past exposure or chronicity. * **Anti-HBs (Antibody to Surface Antigen):** This indicates **immunity**, either through recovery from a natural infection or via vaccination. It appears only after HBsAg has disappeared. **High-Yield Clinical Pearls for NEET-PG:** 1. **First marker to appear:** HBsAg. 2. **Best indicator of infectivity:** HBeAg. 3. **Window Period Marker:** IgM anti-HBc (HBsAg and Anti-HBs are both negative). 4. **Marker of Vaccination:** Anti-HBs is positive; all other markers (including Anti-HBc) are negative. 5. **Chronic Carrier State:** Persistence of HBsAg for >6 months.

Question 135: Which patient with positive sputum requires quarantine?

A. Pregnant women
B. Elderly individuals
C. Children above 6 years of age
D. Children below 6 years of age (Correct Answer)

Explanation: **Explanation:** The correct answer is **Children below 6 years of age**. In the context of infectious disease control, specifically regarding **Tuberculosis (TB)** under the National Tuberculosis Elimination Program (NTEP) guidelines, the management of household contacts is crucial. While "quarantine" in the strictest sense (restricting movement of healthy individuals) is rarely used for TB, the term here refers to the specific clinical protocol for **Chemoprophylaxis**. **Why Option D is correct:** Children under 6 years of age living in the same household as a sputum-positive TB patient are at the highest risk of developing severe, disseminated forms of the disease (like TB Meningitis or Miliary TB) due to their immature immune systems [1]. Regardless of their BCG vaccination status, if they are asymptomatic, they must receive **Isoniazid Preventive Therapy (IPT)** for 6 months (5mg/kg). This "medical quarantine" or protective cover is a high-yield preventive strategy. **Why other options are incorrect:** * **A & B (Pregnant women & Elderly):** While these groups are vulnerable, they are not routinely put under mandatory prophylactic "quarantine" or chemoprophylaxis solely based on contact, unless they are immunocompromised (e.g., HIV positive). * **C (Children above 6 years):** The risk of life-threatening primary complications decreases as the child grows. Routine IPT is prioritized for the <6 age group [1]. **High-Yield Clinical Pearls for NEET-PG:** * **IPT Dosage:** Isoniazid 5 mg/kg daily for 6 months. * **HIV Exception:** All HIV-positive contacts, regardless of age, must receive IPT if active TB is ruled out. * **Reverse Quarantine:** This term is often used for protecting the vulnerable (elderly/infants) from the infected, which is the principle applied here. * **Chemoprophylaxis vs. Treatment:** Always rule out active TB (via symptom screening/X-ray) before starting prophylaxis to prevent drug resistance.

Question 136: Which disease is associated with John Snow, often referred to as the Father of Public Health?

A. Malaria
B. Cholera (Correct Answer)
C. Tuberculosis
D. Plague

Explanation: **Explanation:** **John Snow** is a legendary figure in epidemiology, best known for his work during the **1854 Broad Street cholera outbreak** in London. He famously mapped the cases of cholera and identified a contaminated water pump as the source of the infection. By removing the pump handle, he halted the epidemic. This was a landmark moment in public health because it occurred before the "Germ Theory" was established, proving that cholera was a **water-borne disease** rather than being caused by "miasma" (bad air). **Analysis of Options:** * **A. Malaria:** Associated with **Sir Ronald Ross**, who discovered the transmission of malaria by mosquitoes in Secunderabad, India (Nobel Prize, 1902). * **C. Tuberculosis:** Associated with **Robert Koch**, who discovered *Mycobacterium tuberculosis* in 1882 and formulated Koch’s postulates. * **D. Plague:** Associated with **Alexandre Yersin**, who identified the causative agent *Yersinia pestis*. Historically, the "Great Plague" led to the concept of quarantine, but not specifically to John Snow. **High-Yield Clinical Pearls for NEET-PG:** * **John Snow** is also considered the "Father of Modern Epidemiology." * **Cholera** is caused by *Vibrio cholerae*. The characteristic clinical sign is **"Rice Water Stools."** * The **"Grand Experiment"** by John Snow compared two water companies (Southwark & Vauxhall vs. Lambeth), further proving the water-borne transmission of cholera. * **Epidemiological Triad:** Agent (Vibrio), Host (Human), and Environment (Contaminated water).

Question 137: Hepatitis A virus shedding in feces is observed:

A. One week before the symptoms appear
B. Two weeks after the symptoms appear
C. One week before and one week after the symptoms appear
D. Two weeks before and two weeks after the symptoms appear (Correct Answer)

Explanation: **Explanation:** Hepatitis A Virus (HAV) is primarily transmitted via the **fecal-oral route**. The period of maximum infectivity occurs during the late incubation period, when the viral concentration in the stool is at its peak. **1. Why Option D is Correct:** The shedding of HAV in feces begins approximately **2 weeks before** the onset of clinical symptoms (jaundice) and continues for about **2 weeks after** the symptoms appear. This is a critical epidemiological concept because patients are most infectious *before* they even realize they are ill, leading to rapid community spread. **2. Why Other Options are Incorrect:** * **Option A & C:** These underestimate the duration of viral shedding. Shedding begins earlier than one week before symptoms. * **Option B:** While shedding does occur after symptoms appear, this option ignores the highly infectious pre-icteric phase, which is the hallmark of HAV transmission. **3. High-Yield Clinical Pearls for NEET-PG:** * **Maximum Infectivity:** Occurs during the **2 weeks preceding** the onset of jaundice. By the time jaundice is clinically evident, the viral titer in the stool begins to decline. * **Incubation Period:** 15–50 days (Average: 28 days). * **Diagnosis:** The gold standard for acute infection is the detection of **IgM anti-HAV** antibodies. * **Prevention:** Handwashing and sanitation are key. Post-exposure prophylaxis includes the HAV vaccine or Immunoglobulin (within 2 weeks of exposure). * **Chronic State:** Unlike Hepatitis B and C, Hepatitis A **never** leads to chronic infection or a carrier state.

Question 138: Which date is observed as AIDS Day?

A. April 7
B. May 3
C. June 5
D. December 1 (Correct Answer)

Explanation: **Explanation:** **Correct Answer: D. December 1** World AIDS Day is observed annually on **December 1st**. Established in 1988, it was the first-ever global health day. The primary objective is to raise awareness about the HIV/AIDS pandemic, show support for people living with HIV, and commemorate those who have died from AIDS-related illnesses. In public health, this day serves as a focal point for the **National AIDS Control Programme (NACP)** to promote testing, prevention, and the "95-95-95" targets set by UNAIDS. **Analysis of Incorrect Options:** * **A. April 7:** This is **World Health Day**, marking the founding of the World Health Organization (WHO) in 1948. Each year focuses on a specific global health priority. * **B. May 3:** This is **World Asthma Day** (observed on the first Tuesday of May). It aims to improve asthma awareness and care globally. * **C. June 5:** This is **World Environment Day**, established by the UN to encourage worldwide awareness and action for the protection of the environment. **High-Yield Clinical Pearls for NEET-PG:** * **Red Ribbon:** The international symbol of HIV/AIDS awareness. * **Theme (2023):** "Let Communities Lead." * **Surveillance:** In India, HIV sentinel surveillance is conducted among high-risk groups (HRGs) like FSWs, MSMs, and IDUs. * **Diagnosis:** The screening test of choice is **ELISA**, while the confirmatory test (historically) is the **Western Blot**. However, under current NACO guidelines, a diagnosis is confirmed using three different rapid antibody tests (E/R/S). * **Treatment:** India follows the **"Test and Treat"** policy—initiating ART regardless of CD4 count.

Question 139: What is the most important marker in diagnosing acute Hepatitis B?

A. IgG Anti-HBc
B. Anti HBs
C. IgM Anti-HBc (Correct Answer)
D. HBsAg

Explanation: **Explanation:** The diagnosis of acute Hepatitis B relies on identifying markers that appear during the initial phase of infection. **IgM Anti-HBc** is the most important marker because it is the first antibody to appear and is specifically indicative of a **recent/acute infection** (typically within the last 6 months). **Why IgM Anti-HBc is the correct answer:** It is the only reliable marker during the **"Window Period"**—the interval when HBsAg has disappeared but Anti-HBs has not yet become detectable. Its presence confirms acute replication even when other surface markers are negative. **Analysis of incorrect options:** * **IgG Anti-HBc:** This indicates a past infection or chronic state. It persists for life and does not differentiate between an ongoing chronic infection and a recovered state. * **Anti-HBs:** This antibody signifies **immunity**, either through recovery from a natural infection or via vaccination. It appears only after the acute phase has resolved. * **HBsAg:** While it is the first marker to appear in the blood (indicating the presence of the virus), it cannot distinguish between an **acute** infection and a **chronic carrier** state. **High-Yield Clinical Pearls for NEET-PG:** * **First marker to appear:** HBsAg. * **First antibody to appear:** IgM Anti-HBc. * **Marker of Infectivity:** HBeAg (indicates high viral replication). * **Marker of Recovery/Immunity:** Anti-HBs. * **Vaccination Profile:** Only Anti-HBs is positive; all other markers (including Anti-HBc) are negative. * **Window Period Marker:** IgM Anti-HBc is the sole diagnostic tool.

Question 140: Which of the following statements is true about the rash of chickenpox?

A. Centripetal distribution (Correct Answer)
B. Deep seated lesions
C. Affects palms
D. Slow to evolve

Explanation: ### Explanation **Chickenpox (Varicella)** is caused by the Varicella-Zoster Virus (VZV). Understanding the characteristics of its rash is a high-yield topic for NEET-PG. **Why Option A is Correct:** The rash of chickenpox follows a **centripetal distribution**. This means the lesions are most dense on the trunk (center) and less dense on the extremities (periphery). The rash typically starts on the trunk and then spreads to the face and limbs. **Analysis of Incorrect Options:** * **B. Deep-seated lesions:** Chickenpox lesions are **superficial** and thin-walled, often described as "dewdrops on a rose petal." Deep-seated, firm lesions are characteristic of Smallpox. * **C. Affects palms:** Chickenpox typically **spares the palms and soles**. If a rash involves the palms and soles, clinicians should consider Smallpox, Syphilis, or Hand-Foot-Mouth Disease. * **D. Slow to evolve:** The rash is **rapidly evolving**. It progresses from macule to papule, vesicle, and scab within 24 hours. **Clinical Pearls for NEET-PG:** * **Pleomorphism:** This is the hallmark of chickenpox. Lesions at all stages of development (papules, vesicles, and crusts) are seen simultaneously in the same area. * **Fever:** In chickenpox, the fever usually appears with the onset of the rash (prodromal stage is very short or absent in children). * **Infectivity:** Patients are infectious from 48 hours *before* the rash appears until all lesions have crusted over. * **Scabs:** Unlike Smallpox, the scabs of chickenpox are **not infectious**.

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