Infectious Diseases — MCQs
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The definition of extensively drug-resistant TB includes resistance to all of the following drugs, EXCEPT:
A 45-year-old, healthy nonsmoking woman with a normal BMI (24) has been found on two occasions to have a blood pressure of 145/95. She has no family history of premature coronary artery disease. For this patient, what is the most important next step to take to reduce morbidity and mortality from common medical conditions such as diabetes and cardiovascular disease?
Which of the following is NOT true of Kyasanur Forest Disease?
What is the time gap between the appearance of Koplik's spots and the cutaneous rash in measles?
In RNTCP, what is the schedule for sputum examination after beginning chemotherapy in Category I patients?
What is the clinical incubation period of Filariasis?
Management of non-immunized diphtheria contacts includes all of the following except:
Transmission of hepatitis A virus occurs when?
What is the true infectivity period of hepatitis A?
Which of the following statements is true regarding meningococcal meningitis?
Infectious Diseases Indian Medical PG Practice Questions and MCQs
Question 61: The definition of extensively drug-resistant TB includes resistance to all of the following drugs, EXCEPT:
- A. Rifampicin
- B. Ethambutol (Correct Answer)
- C. Isoniazide
- D. Amikacin
Explanation: **Explanation:** The definition of **Extensively Drug-Resistant Tuberculosis (XDR-TB)** was updated by the WHO in 2021 to reflect changes in treatment regimens. According to the current definition, XDR-TB is TB caused by *Mycobacterium tuberculosis* strains that fulfill the following criteria: 1. **MDR-TB/RR-TB:** Resistance to **Rifampicin** (with or without resistance to **Isoniazid**). 2. **Resistance to any Fluoroquinolone** (e.g., Levofloxacin or Moxifloxacin). 3. **Resistance to at least one additional Group A drug:** This includes **Bedaquiline** or **Linezolid**. **Why Ethambutol is the correct answer:** Ethambutol is a first-line antitubercular drug. While it is often part of the background resistance profile in MDR/XDR cases, its resistance is **not** a defining criterion for the classification of XDR-TB. **Analysis of Incorrect Options:** * **Rifampicin & Isoniazid (Options A & C):** Resistance to these two drugs defines Multi-Drug Resistant TB (MDR-TB). Since XDR-TB is a more severe form of MDR-TB, resistance to these (specifically Rifampicin) is a mandatory prerequisite. * **Amikacin (Option D):** Under the **older (pre-2021) WHO definition**, XDR-TB was defined as MDR-TB plus resistance to any fluoroquinolone and at least one of the three second-line injectable drugs (Amikacin, Capreomycin, or Kanamycin). While no longer a primary defining criterion in the 2021 update, it was historically a core component of the definition. **High-Yield Clinical Pearls for NEET-PG:** * **MDR-TB:** Resistance to at least Isoniazid (H) and Rifampicin (R). * **Pre-XDR-TB:** MDR-TB plus resistance to any Fluoroquinolone. * **Group A Drugs (WHO 2019):** Levofloxacin/Moxifloxacin, Bedaquiline, and Linezolid. These are now the most potent drugs for drug-resistant TB. * **True XDR (2021 Update):** MDR + Fluoroquinolone resistance + (Bedaquiline OR Linezolid) resistance.
Question 62: A 45-year-old, healthy nonsmoking woman with a normal BMI (24) has been found on two occasions to have a blood pressure of 145/95. She has no family history of premature coronary artery disease. For this patient, what is the most important next step to take to reduce morbidity and mortality from common medical conditions such as diabetes and cardiovascular disease?
- A. Urge the patient to quit smoking and discuss the various available medications to assist in the process.
- B. Recommend an exercise program such as brisk walking for at least 30 minutes per day and a low salt, Dietary Approaches to Stop Hypertension (DASH) diet. (Correct Answer)
- C. Prescribe a low-cholesterol diet and statin drug.
- D. Recommend aspirin (81 mg) daily.
Explanation: ### Explanation **1. Why Option B is Correct:** The patient has Stage 1 Hypertension (defined as 140–159/90–99 mmHg per JNC 7/8 guidelines) without comorbidities or high cardiovascular risk. According to the **JNC 8 and AHA/ACC guidelines**, the initial management for Stage 1 hypertension in a low-risk patient is **Therapeutic Lifestyle Changes (TLC)** for 3–6 months before initiating pharmacotherapy. The **DASH diet** (rich in fruits, vegetables, and low-fat dairy) and regular aerobic exercise (brisk walking) are proven to reduce systolic BP by 8–14 mmHg and 4–9 mmHg, respectively, significantly lowering the risk of cardiovascular events and progression to diabetes. **2. Why Other Options are Incorrect:** * **Option A:** The clinical vignette explicitly states the patient is a **nonsmoker**. Counseling for smoking cessation is irrelevant here. * **Option C:** Statins are indicated based on 10-year ASCVD risk scores. This patient has a normal BMI, no family history, and no mentioned dyslipidemia; jumping to pharmacotherapy without a trial of lifestyle modification is premature. * **Option D:** Aspirin is no longer recommended for primary prevention in patients with low cardiovascular risk due to the increased risk of gastrointestinal bleeding, especially when BP is not yet controlled. **3. High-Yield Clinical Pearls for NEET-PG:** * **DASH Diet:** The most effective nutritional intervention for hypertension. It emphasizes high Potassium and Calcium intake. * **Salt Restriction:** Reducing sodium intake to <2.4g/day can reduce SBP by 2–8 mmHg. * **Rule of Halves (Hypertension):** Only half of the people with HTN are diagnosed; half of those diagnosed are treated; and half of those treated are controlled. * **Weight Loss:** For every 10 kg weight loss, SBP can drop by 5–20 mmHg (the most potent TLC if the patient is overweight).
Question 63: Which of the following is NOT true of Kyasanur Forest Disease?
- A. Transmitted by soft ticks
- B. Caused by a retrovirus (Correct Answer)
- C. Incubation period is 3-8 days
- D. A killed vaccine is available
Explanation: **Kyasanur Forest Disease (KFD)**, commonly known as "Monkey Fever," is a viral hemorrhagic fever endemic to the Western Ghats of India. **Explanation of the Correct Answer:** * **Option B (Incorrect Statement):** KFD is **not** caused by a retrovirus. It is caused by the **Kyasanur Forest Disease Virus (KFDV)**, which belongs to the family **Flaviviridae** and the genus *Flavivirus*. It is a single-stranded RNA virus. **Analysis of Other Options:** * **Option A (Incorrect Statement in Question):** This is actually the **incorrect statement** regarding the vector. KFD is transmitted by **Hard Ticks** (*Haemaphysalis spinigera*), not soft ticks. However, in the context of this specific MCQ format where "Retrovirus" is marked as the primary key, it highlights that KFDV is a Flavivirus. (Note: In many exams, both A and B could be considered technically false, but B is a fundamental virological error). * **Option C (True):** The incubation period is typically **3 to 8 days**. The disease often presents with a sudden onset of high-grade fever, headache, and severe myalgia, sometimes followed by a biphasic illness involving neurological symptoms. * **Option D (True):** A **formalin-inactivated (killed) vaccine** is available and used in endemic areas of Karnataka. It requires two primary doses (1 month apart) and periodic boosters. **High-Yield Clinical Pearls for NEET-PG:** * **Reservoirs:** Monkeys (*Black-faced Langur* and *Bonnet Macaque*) are the common hosts; their death is often an early warning sign of an outbreak. * **Vector:** *Haemaphysalis spinigera* (Hard tick). * **Diagnosis:** PCR (early phase) or IgM ELISA. * **Distribution:** First isolated in 1957 from the Kyasanur Forest in Shimoga district, Karnataka. * **Seasonality:** Peak incidence occurs during the dry season (January–June) when human activity in forests increases.
Question 64: What is the time gap between the appearance of Koplik's spots and the cutaneous rash in measles?
- A. 24 hours
- B. 3-4 days (Correct Answer)
- C. 2 weeks
- D. 10 days
Explanation: **Explanation:** Measles (Rubeola) follows a distinct chronological progression of clinical features. The correct answer is **3-4 days** because of the specific timing of the prodromal and eruptive phases. 1. **Why Option B is correct:** Measles has a prodromal stage characterized by the "3 Cs" (Cough, Coryza, Conjunctivitis) and fever. **Koplik’s spots**—the pathognomonic enanthem—typically appear on the buccal mucosa opposite the lower second molars about **2 days before** the rash. The characteristic maculopapular rash (exanthem) usually appears on the **4th day** of the fever. Therefore, the interval between the appearance of Koplik’s spots and the cutaneous rash is approximately **2 to 4 days** (averaging 3-4 days). 2. **Why other options are incorrect:** * **Option A (24 hours):** This is too short; Koplik's spots usually precede the rash by at least 48 hours. * **Option C (2 weeks):** This is the approximate incubation period of Measles (10–14 days), not the interval between clinical signs. * **Option D (10 days):** This is the time from exposure to the onset of the first symptom (fever), not the gap between the spots and the rash. **High-Yield Clinical Pearls for NEET-PG:** * **Koplik’s Spots:** Described as "grains of salt on a red background." They disappear within 24–48 hours after the rash appears. * **Rash Progression:** Starts behind the ears (retro-auricular), spreads to the face/neck, then downwards to the trunk and limbs (cephalocaudal progression). * **Infectivity:** A patient is infectious from **4 days before to 4 days after** the appearance of the rash. * **Vitamin A:** Supplementation is recommended for all children with measles to prevent complications like blindness and pneumonia.
Question 65: In RNTCP, what is the schedule for sputum examination after beginning chemotherapy in Category I patients?
- A. 2, 4, and 6 months (Correct Answer)
- B. 1, 2, and 3 months
- C. 3, 5, and 6 months
- D. 1, 3, and 5 months
Explanation: **Explanation:** Under the **Revised National Tuberculosis Control Programme (RNTCP)**—now transitioned into the National TB Elimination Programme (NTEP)—monitoring treatment response through sputum smear microscopy is a critical component of the DOTS strategy. **1. Why 2, 4, and 6 months is correct:** For **Category I patients** (New cases), the standard treatment duration is 6 months (2 months of Intensive Phase and 4 months of Continuation Phase). Sputum examinations are scheduled at specific milestones to assess bacterial clearance: * **At 2 months:** To check for "Sputum Conversion" at the end of the Intensive Phase (IP). If positive, the IP is no longer extended (as per newer guidelines), but the patient moves to the Continuation Phase (CP) with close monitoring. * **At 4 months:** To monitor progress during the CP. * **At 6 months:** To confirm "Cure" at the end of treatment. **2. Analysis of Incorrect Options:** * **Option B (1, 2, 3 months):** Too frequent; does not cover the end-of-treatment assessment. * **Option C (3, 5, 6 months):** Misses the critical end-of-IP milestone (2 months) used to evaluate early treatment response. * **Option D (1, 3, 5 months):** Does not align with the standard 2-month IP and 6-month completion milestones. **High-Yield Clinical Pearls for NEET-PG:** * **Definition of Cure:** A patient who was initially smear-positive, completed treatment, and had negative smears on at least two occasions, one of which must be at the end of treatment (6th month). * **NTEP Update:** While RNTCP focused on microscopy, the current **NTEP** prioritizes **NAAT (CBNAAT/Truenat)** for diagnosis, but follow-up monitoring still relies on sputum microscopy. * **Category II:** Previously, for retreatment cases, the schedule was 3, 5, and 8 months. However, Category II has been phased out under recent "Daily Regimen" guidelines.
Question 66: What is the clinical incubation period of Filariasis?
- A. 10 to 20 days
- B. 3 to 6 months
- C. 8 to 16 months (Correct Answer)
- D. 6 to 12 months
Explanation: ### Explanation The **clinical incubation period** of Filariasis (specifically Lymphatic Filariasis caused by *Wuchereria bancrofti*) refers to the time interval between the entry of infective larvae ($L_3$) via a mosquito bite and the manifestation of clinical symptoms. **1. Why Option C is Correct:** In Filariasis, the clinical incubation period is typically **8 to 16 months**. This prolonged duration is due to the slow maturation of the larvae into adult worms within the lymphatic system. Clinical symptoms, such as lymphangitis and retrograde fever, only appear once the adult worms begin to cause inflammatory and obstructive changes in the lymphatics. **2. Analysis of Incorrect Options:** * **Option A (10 to 20 days):** This is far too short for Filariasis. This timeframe is more characteristic of the **Pre-patent period** (the time between infection and the appearance of microfilariae in the blood), which is actually about 6–12 months, or the extrinsic incubation period in the mosquito (10–14 days). * **Option B & D (3 to 6 months / 6 to 12 months):** While these represent the time required for larvae to reach the adult stage, they generally precede the onset of overt clinical disease. Clinical symptoms usually lag behind the biological maturation of the parasite. **3. NEET-PG High-Yield Pearls:** * **Extrinsic Incubation Period:** 10 to 14 days (occurs within the *Culex* mosquito). * **Pre-patent Period:** 6 to 12 months (time until microfilariae are detectable in peripheral blood). * **Biological Vector:** *Culex quinquefasciatus* is the most common vector in India. * **Drug of Choice:** Diethylcarbamazine (DEC) 6 mg/kg for 12 days. * **Mass Drug Administration (MDA):** Annual single dose of DEC + Albendazole (or Ivermectin in specific areas).
Question 67: Management of non-immunized diphtheria contacts includes all of the following except:
- A. Prophylactic penicillin, daily throat examinations, and throat swab culture (Correct Answer)
- B. Prophylactic penicillin and throat swab culture
- C. Prophylactic penicillin and daily throat examinations
- D. Single dose of toxoid and throat swab culture
Explanation: ### Explanation The management of **diphtheria contacts** (individuals who have been in close contact with a laboratory-confirmed case) is a high-yield topic for NEET-PG. The primary objective is to prevent the spread of the disease and identify secondary cases early. **Why Option A is Correct:** According to the WHO and Park’s Textbook of Preventive and Social Medicine, the standard management for **non-immunized (susceptible) contacts** includes a comprehensive three-pronged approach: 1. **Chemoprophylaxis:** A single dose of Benzathine Penicillin (IM) or a 7-10 day course of oral Erythromycin to eliminate the carrier state. 2. **Surveillance:** Daily clinical examination for 7 days to detect early signs of the disease. 3. **Bacteriological Screening:** Taking a throat swab for culture to identify asymptomatic carriers. 4. **Immunization:** Immediate initiation of the primary vaccination series (DPT/Td) as they are non-immunized. **Analysis of Other Options:** Options B, C, and D are incorrect because they are **incomplete**. While they contain elements of the protocol (like penicillin or cultures), they omit the essential combination of clinical surveillance, bacteriological testing, and chemoprophylaxis required to safely manage a non-immunized individual. **High-Yield NEET-PG Pearls:** * **Incubation Period:** 2–6 days. * **Drug of Choice for Prophylaxis:** Erythromycin (oral) or Benzathine Penicillin (IM). * **Schick Test:** Historically used to identify susceptibility to diphtheria (positive test = susceptible). * **Contact Definition:** Anyone who has been in close contact with a case within the previous 7 days. * **Diphtheria Antitoxin (ADS):** This is used for **treatment** of clinical cases, **never** for prophylaxis of contacts.
Question 68: Transmission of hepatitis A virus occurs when?
- A. One week before and one week after onset of symptoms
- B. Two weeks before onset of symptoms (Correct Answer)
- C. Two weeks after onset of symptoms
- D. All of the above
Explanation: **Explanation:** The transmission of Hepatitis A Virus (HAV) primarily occurs via the **fecal-oral route**. The period of maximum infectivity is during the late incubation period and the prodromal phase, specifically **two weeks before the onset of clinical jaundice (symptoms)**. **1. Why Option B is correct:** During the two weeks preceding the onset of symptoms, the concentration of HAV in the stool is at its peak (secondary to viral replication in the liver and subsequent excretion in bile). This is the "window of high infectivity" because the patient is asymptomatic but shedding massive amounts of the virus, leading to easy transmission in the community. **2. Why other options are incorrect:** * **Option A & C:** While viral shedding can persist for a short time after symptoms appear, the concentration of the virus in the stool drops significantly once jaundice develops. By the end of the first week of jaundice, the patient is generally considered non-infectious. Therefore, "two weeks after" is clinically inaccurate for the peak transmission period. * **Option D:** Since the infectivity is heavily front-loaded (pre-icteric phase), "All of the above" is incorrect. **High-Yield NEET-PG Pearls:** * **Incubation Period:** 15–45 days (Average: 28 days). * **Secondary Attack Rate (SAR):** High among household contacts. * **Diagnosis:** IgM anti-HAV is the gold standard for acute infection. IgG anti-HAV indicates past infection or immunity. * **Control:** The most effective preventive measure is the Hepatitis A vaccine and improving environmental sanitation (handwashing and safe water). * **Note:** Hepatitis A does **not** lead to chronic carrier states or cirrhosis, unlike Hepatitis B or C.
Question 69: What is the true infectivity period of hepatitis A?
- A. 1-2 weeks before and 2 weeks after the onset of jaundice
- B. 1-2 weeks before and 1 week after the onset of jaundice
- C. 2-3 weeks before and 2 weeks after the onset of jaundice
- D. 2-3 weeks before and 1 week after the onset of jaundice (Correct Answer)
Explanation: **Explanation:** The infectivity of Hepatitis A Virus (HAV) is closely linked to the concentration of the virus excreted in the feces. The maximum viral shedding occurs during the late incubation period and the prodromal (pre-icteric) phase. **1. Why Option D is Correct:** According to standard epidemiological data (Park’s PSM), the period of maximum infectivity for Hepatitis A begins **2 to 3 weeks before** the onset of jaundice and continues for about **1 week after** the appearance of jaundice. By the time jaundice is clinically apparent, the viral titer in the stool begins to decline rapidly, and most patients are non-infectious by the end of the first week of the icteric phase. **2. Analysis of Incorrect Options:** * **Options A & C:** These suggest a 2-week post-jaundice infectivity period. While viral RNA can sometimes be detected longer, the "true infectivity" (the period where transmission is epidemiologically significant) typically ceases after 7 days of jaundice. * **Option B:** This underestimates the pre-icteric infectivity. The virus starts shedding significantly as early as 2-3 weeks before symptoms appear, making this the most dangerous period for community transmission. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mode of Transmission:** Primarily feco-oral; common in areas with poor sanitation. * **Secondary Attack Rate (SAR):** High among household contacts (approx. 20%). * **Diagnosis:** IgM anti-HAV is the gold standard for acute infection. * **Vaccination:** Live attenuated (H2 strain) or Inactivated vaccines are available. * **Post-exposure Prophylaxis:** Best given within 2 weeks of exposure (Vaccine or Immunoglobulin). * **Key Fact:** Hepatitis A does **not** cause chronic infection or a carrier state.
Question 70: Which of the following statements is true regarding meningococcal meningitis?
- A. The case fatality rate is less than 10% in untreated cases.
- B. Asymptomatic carriers are the main source of infection.
- C. Rifampicin is the drug of choice for treatment.
- D. Treatment within the first 2 days can save the lives of 95% of cases. (Correct Answer)
Explanation: **Explanation:** Meningococcal meningitis, caused by *Neisseria meningitidis*, is a medical emergency characterized by rapid progression. **Why Option D is Correct:** Early diagnosis and prompt initiation of effective antibiotic therapy are the most critical factors in determining prognosis. Clinical studies and epidemiological data (Park’s PSM) indicate that if treatment is started within the first **24 to 48 hours** of symptom onset, the survival rate is significantly high, saving approximately **95% of cases**. **Analysis of Incorrect Options:** * **Option A:** In **untreated** cases, the case fatality rate (CFR) is extremely high, often reaching **50% or more**. Even with modern therapy, the CFR remains around 5–10%. * **Option B:** While carriers exist, the primary source of infection in an endemic setup is the **clinical case** (especially in the early stages) and subclinical cases. However, in the context of transmission dynamics, the "carrier to case" ratio is high, but the question asks for the "main source" in a clinical context. (Note: Some texts emphasize carriers for transmission, but Option D is a more definitive "true" statement in standard textbooks). * **Option C:** **Ceftriaxone** (or Penicillin G) is the drug of choice for **treatment**. Rifampicin is primarily used for **chemoprophylaxis** of close contacts, not for treating the active disease. **High-Yield Clinical Pearls for NEET-PG:** * **Chemoprophylaxis of choice:** Rifampicin (Adults: 600mg BD for 2 days). Alternatives: Ciprofloxacin (single dose) or Ceftriaxone (IM). * **Vaccine:** Quadrivalent (A, C, Y, W-135) is commonly used. Group B is poorly immunogenic. * **Characteristic Sign:** Petechial or purpuric rash (indicates meningococcemia). * **Incubation Period:** 3 to 4 days (Range: 2–10 days).
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