Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 81: A 30-year-old female has sputum-positive tuberculosis. Her child is 3 years old. What is the recommended chemoprophylaxis for the child?

A. Isoniazid 3 mg/kg for 3 months
B. Isoniazid 5 mg/kg for 3 months
C. Isoniazid 3 mg/kg for 6 months
D. Isoniazid 5 mg/kg for 6 months (Correct Answer)

Explanation: **Explanation:** The correct answer is **D. Isoniazid 5 mg/kg for 6 months.** **1. Underlying Medical Concept:** In the context of the National Tuberculosis Elimination Program (NTEP) in India, chemoprophylaxis (Preventive Treatment) is mandatory for "high-risk" contacts of a sputum-positive pulmonary TB patient. Children under 5 years of age are particularly vulnerable to progressing from infection to active disease (including severe forms like TB meningitis). The standard protocol for Isoniazid Preventive Therapy (IPT) is the administration of **Isoniazid (INH)** at a dose of **5 mg/kg daily for a duration of 6 months**, regardless of their BCG vaccination status, provided active TB has been ruled out. **2. Why Incorrect Options are Wrong:** * **Options A & C (3 mg/kg):** This is a sub-therapeutic dose for prophylaxis. The established dose for INH prophylaxis in children is 5 mg/kg (up to a maximum of 300 mg/day). * **Option B (3 months):** While some newer shorter regimens (like 3 months of weekly Rifapentine + INH) exist in global guidelines, the standard traditional IPT under NTEP for pediatric contacts remains 6 months. A 3-month duration of INH alone is insufficient to ensure sterilization of latent bacilli. **3. High-Yield Clinical Pearls for NEET-PG:** * **Target Group:** All household contacts <5 years of age and all HIV-positive individuals must receive IPT after ruling out active TB. * **Pyridoxine Supplementation:** To prevent peripheral neuropathy, Pyridoxine (10 mg/day) should be co-administered with INH, especially in malnourished children. * **Exclusion:** Before starting IPT, always rule out active TB using the "4S" screening (Cough, Fever, Weight loss, Night sweats) and a chest X-ray if necessary. * **Newer Regimen:** Note that NTEP is transitioning towards **3HP** (3 months of weekly Isoniazid and Rifapentine) for TB Preventive Treatment (TPT), but 6H (6 months of INH) remains a standard exam-favorite answer.

Question 82: Which of the following are considered risk factors for tuberculosis?

A. HIV
B. Type 1 diabetes mellitus
C. Chronic renal failure
D. All of the above (Correct Answer)

Explanation: **Explanation:** The correct answer is **D. All of the above.** The underlying medical concept is **Immunosuppression.** Tuberculosis (TB) is an opportunistic infection; any condition that impairs the body’s cell-mediated immunity (specifically T-cell function) increases the risk of progressing from latent TB infection to active disease. * **HIV (Option A):** This is the most potent risk factor for TB. HIV depletes CD4+ T-lymphocytes, which are essential for forming granulomas to contain *Mycobacterium tuberculosis*. An HIV-positive individual has a 20–30 times higher risk of developing active TB compared to someone HIV-negative. * **Type 1 Diabetes Mellitus (Option B):** Hyperglycemia impairs chemotaxis, phagocytosis, and the bactericidal activity of macrophages and neutrophils. Both Type 1 and Type 2 DM are significant risk factors, increasing the risk of TB by approximately 3-fold. * **Chronic Renal Failure (Option C):** Patients with CRF or those on hemodialysis have impaired cellular immunity and uremia-induced immune dysfunction, making them highly susceptible to reactivation of latent TB. **Clinical Pearls for NEET-PG:** * **Most common opportunistic infection in HIV:** Tuberculosis (in India). * **Other high-yield risk factors:** Silicosis (increases risk by 30x), prolonged corticosteroid use, malnutrition (low BMI), and TNF-alpha inhibitors. * **Social factors:** Overcrowding, poor ventilation, and low socioeconomic status are key environmental determinants. * **Screening:** In high-risk groups (like HIV), the Tuberculin Skin Test (TST) is considered positive at an induration of **≥5 mm**.

Question 83: Regarding Schick's test, which of the following is false?

A. An erythematous reaction in both arms indicates hypersensitivity.
B. A positive test means that the person is immune to Diphtheria. (Correct Answer)
C. Diphtheria toxin is given intradermally.
D. The test is done to find out the immune status against diphtheria.

Explanation: ### Explanation **1. Why the Correct Answer is Right:** The **Schick test** is used to determine **susceptibility** to Diphtheria, not immunity. A **Positive Test** (characterized by erythema and swelling at the toxin injection site) indicates that the individual lacks sufficient circulating antitoxin to neutralize the toxin. Therefore, a positive test means the person is **susceptible** (non-immune) to Diphtheria. Conversely, a negative test indicates that the person has enough antibodies to neutralize the toxin and is immune. **2. Analysis of Incorrect Options:** * **Option A (True statement):** If both arms (test arm with toxin and control arm with toxoid) show a reaction that fades quickly, it is a **False Reaction**, indicating **hypersensitivity** to the bacterial proteins rather than a lack of immunity. * **Option C (True statement):** The test involves the **intradermal** injection of 0.1 ml of Schick test toxin into the forearm. * **Option D (True statement):** The primary clinical purpose of the Schick test is to assess the **immune status** of an individual or a population against *Corynebacterium diphtheriae*. **3. NEET-PG High-Yield Pearls:** * **The Control:** The control arm receives **heat-inactivated toxin** (toxoid) to distinguish between a true positive reaction and hypersensitivity. * **Interpretation Summary:** * **Positive:** Reaction only on the test arm (Susceptible). * **Negative:** No reaction on either arm (Immune). * **Pseudo-reaction:** Erythema on both arms, disappearing by the 4th day (Immune but hypersensitive). * **Combined:** Reaction on both arms, but the test arm reaction persists longer (Susceptible and hypersensitive). * **Current Relevance:** The Schick test is largely obsolete in clinical practice today, replaced by more accurate serological assays for antitoxin titers.

Question 84: A patient has been recently put on the DOTS Plus regimen. Which of the following drug combinations is included in the treatment of this patient?

A. 2 months of Isoniazid, Rifampicin, Ethambutol + 4 months of Isoniazid, Rifampicin
B. 2 months of Isoniazid, Rifampicin, Pyrazinamide, Ethambutol, Streptomycin + 6 months of Isoniazid, Rifampicin, Ethambutol
C. 6 months of Isoniazid, Rifampicin, Kanamycin, Ofloxacin + 18 months of Ofloxacin, Kanamycin
D. 6 months of Kanamycin, Ofloxacin, Ethionamide, Cycloserine, Pyrazinamide, Ethambutol + 18 months of Ofloxacin, Ethionamide, Cycloserine, Ethambutol (Correct Answer)

Explanation: ### Explanation **Concept Overview:** The **DOTS Plus** regimen is specifically designed for the management of **Multi-Drug Resistant Tuberculosis (MDR-TB)**, defined as resistance to at least Isoniazid and Rifampicin. Unlike the standard DOTS for drug-sensitive TB, DOTS Plus utilizes second-line drugs and involves a significantly longer treatment duration (24 months). **Why Option D is Correct:** The conventional MDR-TB regimen under RNTCP (now NTEP) consists of two phases: 1. **Intensive Phase (IP):** 6 to 9 months of six drugs: **K**anamycin (Injectable), **O**floxacin (Fluoroquinolone), **E**thionamide, **C**ycloserine, **P**yrazinamide, and **E**thambutol. 2. **Continuation Phase (CP):** 18 months of four drugs: **O**floxacin, **E**thionamide, **C**ycloserine, and **E**thambutol. (Injectables and Pyrazinamide are stopped). **Analysis of Incorrect Options:** * **Option A:** This is the standard **6-month Short Course Chemotherapy** for drug-sensitive TB (New cases). * **Option B:** This represents the old **Category II regimen** (8 months) previously used for "Retreatment" cases, which has now been phased out in favor of Universal Drug Susceptibility Testing (UDST). * **Option C:** While it includes some second-line drugs, the duration and drug combinations do not match the standardized RNTCP protocol for MDR-TB. **High-Yield Clinical Pearls for NEET-PG:** * **MDR-TB Definition:** Resistance to **Isoniazid (H) + Rifampicin (R)**. * **XDR-TB Definition:** MDR-TB + resistance to any **Fluoroquinolone** + at least one **second-line injectable** (Kanamycin, Capreomycin, or Amikacin). * **Current Update:** India is moving towards **all-oral H-mono/poly resistance regimens** and shorter MDR-TB regimens (9–11 months) containing **Bedaquiline**, but the conventional 24-month DOTS Plus regimen remains a classic exam favorite. * **Pyrazinamide** is used throughout the Intensive Phase of MDR-TB treatment because of its unique ability to kill dormant bacilli in acidic environments.

Question 85: According to the modified plan of operation, endemic areas were classified based on what parameter?

A. Annual Parasite Index (API) (Correct Answer)
B. Age-Breakdown of Residuals (ABER)
C. Slide positivity rate
D. Slide falciparum rate

Explanation: ### Explanation The **Modified Plan of Operation (MPO)** was launched in **1977** under the National Malaria Eradication Programme (NMEP) to tackle the rising incidence of malaria and the emergence of insecticide resistance. **1. Why API is the Correct Answer:** The Annual Parasite Index (API) is the most critical indicator used to measure the incidence of malaria in a community. Under the MPO, areas were classified based on their API to determine the strategy for intervention: * **API > 2:** High-risk areas requiring intensive **Indoor Residual Spraying (IRS)** with insecticides. * **API < 2:** Low-risk areas where the focus shifted to surveillance and focal spray if outbreaks occurred. The API is calculated as: *(Total number of positive slides / Total population) × 1000*. **2. Why Other Options are Incorrect:** * **B. ABER (Annual Blood Examination Rate):** This measures the **operational efficiency** of the surveillance system (target is >10%), not the endemicity of the disease. * **C. Slide Positivity Rate (SPR):** While it indicates the prevalence of malaria among symptomatic patients, it was not the primary metric for classification under MPO. * **D. Slide Falciparum Rate (SFR):** This measures the proportion of *P. falciparum* cases, used to monitor the severity and risk of cerebral malaria, but not for general area classification. **Clinical Pearls for NEET-PG:** * **MPO Goal:** To prevent deaths and reduce morbidity; it shifted the focus from "eradication" to "effective control." * **API vs. ABER:** Remember, **API** measures the **disease burden**, while **ABER** measures the **program's performance**. * **Current Strategy:** India currently follows the National Framework for Malaria Elimination (2016–2030), categorizing states into Category 0 (Elimination) to Category 3 (High Burden) based on API.

Question 86: Which of the following should be injected in and around the wound in a class III rabies bite?

A. Tetanus toxoid
B. Antibiotic solution
C. Anti-rabies serum (Correct Answer)
D. None of the above

Explanation: **Explanation:** The management of a Category III rabies bite (single or multiple transdermal bites, scratches, or contamination of mucous membranes with saliva) requires immediate local wound treatment, active immunization (vaccine), and passive immunization. **1. Why Anti-rabies Serum (RIG) is correct:** The primary goal in Category III bites is to neutralize the virus at the site of entry before it can invade the peripheral nerves. **Rabies Immunoglobulin (RIG)** or Anti-rabies serum provides immediate, pre-formed antibodies. According to WHO and National guidelines, as much of the calculated dose of RIG as anatomically feasible must be **infiltrated in and around the wound(s)**. This creates a "protective barrier" of antibodies at the exact site of viral inoculation. **2. Why other options are incorrect:** * **Tetanus toxoid:** While tetanus prophylaxis is part of wound management, it is administered intramuscularly (usually in the deltoid), not infiltrated into the bite wound. * **Antibiotic solution:** Routine infiltration of antibiotics into a bite wound is not recommended. Systemic antibiotics may be prescribed orally if the wound appears infected or is deep, but they do not prevent rabies. **Clinical Pearls for NEET-PG:** * **Dosage:** Human RIG (HRIG) is 20 IU/kg; Equine RIG (ERIG) is 40 IU/kg. * **Site:** If any serum remains after infiltration, it should be injected IM at a site distant from the vaccine injection site. * **Timing:** RIG should be administered as soon as possible (Day 0). It is not recommended beyond 7 days after the first dose of the vaccine, as the body begins producing its own antibodies by then. * **Wound Suturing:** Should be avoided. If necessary, it must be done only after infiltrating RIG and delayed by a few hours.

Question 87: Measles is infective for how many days before the onset of rash?

A. 10 days
B. 4 days (Correct Answer)
C. 1 day
D. On the same day

Explanation: ### Explanation **Correct Option: B (4 days)** The period of communicability for Measles (Rubeola) is defined as **4 days before to 5 days after** the appearance of the rash. This period coincides with the peak of viral shedding from the respiratory tract. The infectivity is highest during the **prodromal stage** (pre-eruptive phase), characterized by the "3 Cs" (Cough, Coryza, Conjunctivitis) and Koplik spots, even before the characteristic maculopapular rash appears. **Analysis of Incorrect Options:** * **Option A (10 days):** This is too long. While the incubation period of Measles is approximately 10–14 days, the patient is not infectious during the early incubation phase. * **Option C (1 day):** This underestimates the window of transmission. Viral shedding begins significantly earlier than 24 hours before the rash. * **Option D (Same day):** This is clinically dangerous to assume. Measles is most contagious *before* the rash appears; by the time the rash is visible, the patient has already been infectious for several days. **High-Yield Clinical Pearls for NEET-PG:** * **Secondary Attack Rate (SAR):** Measles has one of the highest SARs (>90%) among susceptible household contacts. * **Koplik Spots:** These are pathognomonic and appear 1–2 days before the rash on the buccal mucosa opposite the lower second molars. * **Isolation:** A child with measles should be isolated for at least 4 days after the rash appears to prevent transmission. * **Vaccination:** The Measles vaccine is a live attenuated vaccine (Edmonston-Zagreb strain in India) usually given at 9 months and 16–24 months. * **Vitamin A:** Supplementation is recommended for all children with acute measles to prevent complications like blindness and pneumonia.

Question 88: Which of the following strategies is NOT included in preventing HIV transmission?

A. Education
B. Treatment of sexually transmitted diseases
C. Antiretroviral treatment (Correct Answer)
D. Condoms

Explanation: **Explanation:** The goal of HIV prevention strategies is to reduce the incidence of new infections by targeting behavioral, biological, and structural factors. **Why Antiretroviral Treatment (ART) is the correct answer:** In the context of traditional public health prevention strategies (as per standard textbooks like Park’s Preventive and Social Medicine), **Antiretroviral Treatment (ART)** is primarily classified as a **tertiary prevention** measure aimed at clinical management, improving the quality of life, and reducing mortality in those already infected. While modern concepts like "Treatment as Prevention" (TasP) exist, ART itself is a therapeutic intervention for the patient rather than a primary prevention tool for the general population. **Analysis of Incorrect Options:** * **Education (A):** This is the cornerstone of **Primary Prevention**. Health education regarding safe practices, needle sharing, and risk reduction is the most effective way to prevent the spread of HIV. * **Treatment of STDs (B):** STDs cause mucosal inflammation or ulcers, which significantly increase the biological vulnerability to HIV. Treating STDs reduces the "portal of entry," thereby acting as a preventive strategy. * **Condoms (D):** These act as a **primary barrier protection** (Mechanical Prophylaxis). Consistent and correct use of condoms is one of the most effective methods to prevent sexual transmission of HIV. **NEET-PG High-Yield Pearls:** * **Post-Exposure Prophylaxis (PEP):** Must be started within **72 hours** of exposure (ideally within 2 hours) and continued for 28 days. * **Window Period:** The time between infection and the appearance of detectable antibodies (usually 2–12 weeks). * **Screening Test:** ELISA (High sensitivity). * **Confirmatory Test:** Western Blot (High specificity); however, the current WHO/NACO strategy uses a series of three rapid antibody tests for diagnosis. * **Vertical Transmission:** The risk is highest during delivery; Nevirapine or Zidovudine regimens are used to reduce this risk.

Question 89: Which of the following statements is true about COVID-19?

A. COVID-19 is a type of influenza virus.
B. Those who take flu vaccine are immune to COVID-19.
C. It is a new strain which originated in Wuhan, China. (Correct Answer)
D. All cases of COVID-19 are symptomatic.

Explanation: **Explanation:** **Correct Answer: C. It is a new strain which originated in Wuhan, China.** COVID-19 is caused by the **SARS-CoV-2** virus, a novel strain of the Coronaviridae family that had not been previously identified in humans. The initial outbreak was epidemiologically linked to the Huanan Seafood Wholesale Market in **Wuhan, Hubei Province, China**, in December 2019. It is a zoonotic pathogen that likely jumped from animals to humans. **Analysis of Incorrect Options:** * **Option A:** COVID-19 is caused by a **Coronavirus** (enveloped, positive-sense RNA virus), not an Influenza virus (Orthomyxoviridae). While both cause respiratory illness, they belong to entirely different viral families. * **Option B:** The flu vaccine protects against specific strains of the Influenza virus. There is **no cross-immunity** between the influenza vaccine and SARS-CoV-2. * **Option D:** A significant proportion of COVID-19 cases (estimated 20-40%) are **asymptomatic** or presymptomatic, yet these individuals can still transmit the virus to others. **High-Yield Clinical Pearls for NEET-PG:** * **Receptor:** SARS-CoV-2 binds to the **ACE-2 (Angiotensin-Converting Enzyme 2)** receptors, primarily found in Type II pneumocytes. * **Incubation Period:** Average 5–6 days (Range: 1–14 days). * **Gold Standard Test:** Real-time Reverse Transcription Polymerase Chain Reaction (**RT-PCR**). * **Infectivity Period:** Maximum viral shedding occurs in the early stages of the illness (2 days before to 5 days after symptom onset). * **Cytokine Storm:** Severe cases are characterized by an overproduction of pro-inflammatory cytokines (IL-6, TNF-alpha).

Question 90: Which of the following is not true about the National AIDS Control Programme?

A. Sentinel surveillance methodology has been adopted.
B. Community-based screening for the prevalence of HIV has been taken up. (Correct Answer)
C. Early diagnosis and treatment of STD is one of the major strategies to control the spread of HIV.
D. Guidelines for blood banks, blood donors, and dialysis units are formulated.

Explanation: ### Explanation The National AIDS Control Programme (NACP) focuses on targeted interventions and surveillance rather than mass population screening. **1. Why Option B is the Correct Answer (The "Not True" Statement):** In India, **community-based screening** (mass screening) for the general population is **not** a strategy under NACP. HIV testing is strictly voluntary, confidential, and requires informed consent (VCT - Voluntary Counseling and Testing). Mass screening is considered cost-ineffective and ethically challenging due to the low prevalence in the general population and the potential for social stigma. Instead, the program focuses on **Targeted Interventions (TI)** for High-Risk Groups (HRGs) like FSWs, MSM, and IDUs. **2. Analysis of Incorrect Options:** * **Option A:** **Sentinel Surveillance** is the backbone of NACP. It involves monitoring specific groups (e.g., ANC attendees, HRGs) at regular intervals to track the trend and spread of the epidemic without testing every individual in the country. * **Option C:** There is a strong epidemiological link between STDs and HIV. STDs increase the risk of HIV transmission by 2–9 times. Therefore, **Syndromic Management of STIs** is a core strategy of NACP to reduce HIV vulnerability. * **Option D:** Ensuring **Blood Safety** is a primary objective. NACP formulates strict guidelines for mandatory screening of all donated blood for HIV, HBV, HCV, Malaria, and Syphilis to prevent transfusion-transmitted infections. **Clinical Pearls for NEET-PG:** * **NACP Phase V (2021–2026):** Currently active, aiming for the **95-95-95 targets** by 2025 and ending the AIDS epidemic as a public health threat by 2030. * **Sentinel Surveillance:** Shifted to **HIV Estimates** and **IBBS** (Integrated Biological and Behavioral Surveillance) in recent years. * **Red Ribbon Clubs:** Formed in colleges to create awareness among the youth. * **First Case in India:** Reported in 1986 (Chennai). NACP-I started in 1992.

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HIV/AIDS Control Program

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