Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 21: What is the recommended period of isolation for shigellosis?

A. Until 1 negative stool culture.
B. Until 2 consecutive negative stool cultures.
C. Until 3 consecutive negative stool cultures. (Correct Answer)
D. None of the above.

Explanation: **Explanation:** Shigellosis (Bacillary Dysentery) is a highly infectious disease caused by *Shigella* species. The primary reason for stringent isolation protocols is the **low infectious dose**; as few as 10–100 organisms can cause clinical disease. **Why Option C is Correct:** According to standard public health guidelines (and Park’s Textbook of Preventive and Social Medicine), a case of shigellosis is considered non-infectious only after clinical recovery and the documentation of **three consecutive negative stool cultures** taken at intervals of at least 24 hours. This rigorous requirement ensures that the patient is not a "convalescent carrier," thereby preventing outbreaks, especially in high-risk settings like daycare centers or food-handling establishments. **Why Other Options are Incorrect:** * **Option A & B:** A single or even two negative cultures are insufficient because *Shigella* shedding can be intermittent. Relying on fewer than three cultures increases the risk of a false negative, potentially allowing a carrier to return to the community while still being infectious. * **Option D:** This is incorrect as specific isolation and clearance criteria are well-established for enteric pathogens. **High-Yield Clinical Pearls for NEET-PG:** * **Mode of Transmission:** Primarily fecal-oral (the "4 Fs": Fingers, Flies, Food, and Fomites). * **Incubation Period:** Usually 1–7 days (commonly 48 hours). * **Drug of Choice:** Ciprofloxacin is generally the first-line treatment, though resistance is increasing (Azithromycin or Ceftriaxone are alternatives). * **Key Difference:** Unlike Typhoid (which requires 3 negative cultures for clearance in food handlers), Shigellosis is more acutely infectious due to its extremely low threshold for infection.

Question 22: The '3 by 5 Initiative' was launched in developing countries to combat which of the following?

A. HIV/AIDS (Correct Answer)
B. Malaria
C. SARS
D. Tuberculosis

Explanation: **Explanation:** The **'3 by 5' Initiative** was a global health strategy launched by the **World Health Organization (WHO)** and **UNAIDS** in December 2003. The specific goal was to provide antiretroviral therapy (ART) to **3 million people** living with **HIV/AIDS** in low- and middle-income countries by the end of **2005**. It was a landmark effort to shift the focus from HIV prevention alone to include equitable access to life-saving treatment. **Analysis of Options:** * **HIV/AIDS (Correct):** The initiative targeted the treatment gap in developing nations, promoting the "public health approach" to ART, which simplified treatment regimens and clinical monitoring to scale up delivery. * **Malaria:** While the "Roll Back Malaria" partnership exists, the '3 by 5' branding is specific to HIV treatment targets. * **SARS:** The SARS outbreak (2003) led to strengthened International Health Regulations (IHR), but no specific '3 by 5' initiative was associated with it. * **Tuberculosis:** TB control is primarily managed through the DOTS (Directly Observed Treatment, Short-course) strategy and the "End TB" strategy. **High-Yield Clinical Pearls for NEET-PG:** * **Goal:** 3 million people on ART by 2005. * **Current Target:** The '3 by 5' initiative paved the way for the **95-95-95 targets** (95% diagnosed, 95% on ART, 95% virally suppressed by 2030). * **ART in India:** Free ART was launched in India on **April 1, 2004**, as part of this global momentum. * **NACP Phase:** This initiative coincided with the transition between NACP-II and NACP-III in India.

Question 23: Class II exposure in animal bites includes which of the following?

A. Bites from wild animals
B. Licks on a fresh wound
C. Scratch with oozing of blood
D. Scratches without oozing of blood (Correct Answer)

Explanation: The classification of animal bites is a high-yield topic for NEET-PG, based on the **WHO and National Guidelines on Rabies Prophylaxis**. The categorization determines the post-exposure prophylaxis (PEP) protocol. ### **Explanation of the Correct Option** **Option D (Scratches without oozing of blood)** is the correct definition of **Category II exposure**. Category II involves minor abrasions or scratches without bleeding, or nibbling of uncovered skin. These exposures carry a moderate risk of rabies transmission because the virus can enter through microscopic breaks in the skin, even if no gross bleeding is visible. * **Management:** Immediate wound washing and administration of the **Anti-Rabies Vaccine (ARV)**. ### **Analysis of Incorrect Options** * **Option A (Bites from wild animals):** Regardless of the severity of the wound, all bites from wild animals (e.g., foxes, jackals) are automatically classified as **Category III** due to the high viral load and high risk of transmission. * **Option B (Licks on a fresh wound):** Licks on broken skin or fresh wounds allow direct contact between saliva and the bloodstream/mucosa. This is classified as **Category III**. * **Option C (Scratch with oozing of blood):** Any scratch or bite that causes transdermal bleeding (oozing) is classified as **Category III**. ### **High-Yield Clinical Pearls for NEET-PG** * **Category I:** Touching/feeding animals or licks on **intact** skin. (Management: No PEP, only wound washing). * **Category III Management:** Requires **ARV + Rabies Immunoglobulin (RIG)**. RIG should be infiltrated into and around the wound. * **Site of Injection:** ARV is given Intramuscularly (Deltoid) or Intradermally. **Never** give ARV in the gluteal region as fat reduces vaccine efficacy. * **Wound Care:** Immediate flushing with soap and water for **15 minutes** is the most effective first-aid measure. Avoid suturing the wound; if necessary, do it after 24–48 hours under RIG cover.

Question 24: Transmission of an agent by vectors is facilitated by which of the following mechanisms, except one?

A. Contamination with body fluids of vectors
B. Scratching-in of infected feces
C. Ingestion of infected material (Correct Answer)
D. Regurgitation

Explanation: This question tests the conceptual understanding of **Vector-borne Transmission** mechanisms. ### **Explanation of the Correct Answer** **Option C (Ingestion of infected material)** is the correct answer because it describes **Vehicle-borne transmission**, not vector-borne transmission. Ingestion involves the entry of an agent through the oral route via contaminated food, water, or milk. While a vector (like a housefly) can physically carry pathogens to food, the act of "ingestion" is the final step of vehicle transmission, whereas vector transmission specifically refers to the biological or mechanical process involving an arthropod intermediary. ### **Analysis of Incorrect Options (Mechanisms of Vector Transmission)** * **A. Contamination with body fluids:** Some vectors transmit diseases when they are crushed on the skin, releasing infected body fluids (haemolymph). Example: **Louse-borne Relapsing Fever**. * **B. Scratching-in of infected feces:** Known as **posterior station inoculation**. The vector defecates while feeding, and the host inadvertently scratches the infected feces into the bite wound. Example: **Chagas disease** (Triatomine bug) and **Epidemic Typhus** (Louse). * **D. Regurgitation:** Some vectors transmit pathogens by vomiting infected gut contents into the host's blood during a blood meal. Example: **Plague** (Xenopsylla cheopis) due to "blocking" of the proventriculus. ### **High-Yield NEET-PG Pearls** * **Inoculation:** The most common mechanism where the agent is injected via saliva during a bite (e.g., Malaria, Filariasis). * **Biological Transmission types:** * *Propagative:* Only multiplication (e.g., Plague). * *Cyclo-propagative:* Multiplication + Developmental change (e.g., Malaria). * *Cyclo-developmental:* Only developmental change, no multiplication (e.g., Filaria). * **Extrinsic Incubation Period:** The time required for the pathogen to develop inside the vector before it becomes infective.

Question 25: SIDA functions for which of the following?

A. Leprosy
B. Tuberculosis (Correct Answer)
C. Blindness
D. Agriculture

Explanation: **Explanation:** The correct answer is **Tuberculosis (B)**. **SIDA** stands for the **Swedish International Development Cooperation Authority**. In the context of public health in India, SIDA has been a major international partner specifically for the **National Tuberculosis Elimination Programme (NTEP)**, formerly known as the RNTCP. 1. **Why Tuberculosis is correct:** SIDA played a pivotal role in the 1990s by providing financial and technical support for the pilot projects of **DOTS (Directly Observed Treatment, Short-course)** in India. Their support was instrumental in the phased expansion of the RNTCP across the country, focusing on drug procurement and laboratory strengthening. 2. **Why other options are incorrect:** * **Leprosy:** The primary international partner for the National Leprosy Eradication Programme (NLEP) is the **WHO** and **ILEP** (International Federation of Anti-Leprosy Associations), along with significant support from the Sasakawa Health Foundation. * **Blindness:** The National Programme for Control of Blindness (NPCB) receives major international assistance from the **World Bank** and organizations like **DANIDA** (Danish International Development Agency). * **Agriculture:** While SIDA does fund rural development, in the medical curriculum and NEET-PG context, it is strictly associated with its landmark contribution to the TB control program. **High-Yield Clinical Pearls for NEET-PG:** * **DANIDA:** Associated with Blindness Control and National Family Welfare programs. * **USAID:** Associated with HIV/AIDS (PACE project) and Maternal & Child Health. * **Rockefeller Foundation:** Historically famous for Hookworm control and supporting the development of the Yellow Fever vaccine (17-D strain). * **CARE:** Primarily focuses on Integrated Child Development Services (ICDS) and nutrition.

Question 26: What is the recommended dose of Rabies immunoglobulin?

A. 10 IU/Kg body weight
B. 15 IU/kg body weight
C. 20 IU/kg body weight (Correct Answer)
D. 25 IU/kg body weight

Explanation: **Explanation:** The correct dose of **Equine Rabies Immunoglobulin (ERIG)** is **40 IU/kg body weight**, whereas the dose for **Human Rabies Immunoglobulin (HRIG)** is **20 IU/kg body weight**. In the context of standard medical examinations like NEET-PG, when "Rabies Immunoglobulin" is mentioned without specifying the type, the question typically refers to HRIG, making **20 IU/kg** the standard answer. **Why 20 IU/kg is correct:** Rabies Immunoglobulin (RIG) provides **passive immunity** by delivering immediate neutralizing antibodies at the site of the bite before the patient’s own immune system can respond to the vaccine (active immunity). The dose of 20 IU/kg for HRIG is calculated to provide sufficient neutralization without interfering with the subsequent immune response triggered by the rabies vaccine. **Analysis of Incorrect Options:** * **10 IU/kg & 15 IU/kg:** These doses are sub-therapeutic. They do not provide a high enough concentration of antibodies to effectively neutralize the virus at the wound site, increasing the risk of treatment failure. * **25 IU/kg:** This exceeds the recommended dose for HRIG. Over-administration of RIG can lead to "immune interference," where the excess passive antibodies suppress the body’s ability to produce its own antibodies in response to the rabies vaccine. **High-Yield Clinical Pearls for NEET-PG:** * **Administration:** RIG should be infiltrated **in and around the wound**. Any remaining volume should be injected intramuscularly at a site distant from the vaccine injection. * **Window Period:** RIG is only indicated up to **7 days** after the first dose of the vaccine. Beyond day 7, the body starts producing its own antibodies, making RIG unnecessary. * **Category III Bites:** RIG is mandatory for all Category III exposures (transdermal bites/scratches) and Category II exposures in immunocompromised individuals. * **Calculation Tip:** Remember the "20/40 Rule"—20 IU/kg for Human (HRIG) and 40 IU/kg for Equine (ERIG).

Question 27: "3 BY 5 target" approach refers to?

A. Providing 3 antiretroviral drugs to all patients by 2005
B. Providing antiretroviral therapy to 3 million people by 2005 (Correct Answer)
C. Providing 3 antiretroviral drugs to all patients
D. All of the above

Explanation: ### Explanation The **"3 by 5" initiative** was a global public health strategy launched by the World Health Organization (WHO) and UNAIDS in December 2003. **1. Why Option B is Correct:** The core objective of this initiative was to provide **Antiretroviral Therapy (ART)** to **3 million people** living with HIV/AIDS in low- and middle-income countries by the end of the year **2005**. At the time, it was a landmark effort to shift HIV management from prevention-only to a combined approach of prevention and universal access to treatment. **2. Why Other Options are Incorrect:** * **Option A & C:** While standard ART typically involves a combination of **three** drugs (Triple Drug Therapy), the "3" in the "3 by 5" target specifically refers to the **number of people (3 million)**, not the number of drugs. * **Option D:** Since the target was specific to a population count and a deadline, "All of the above" is factually incorrect. **3. High-Yield Clinical Pearls for NEET-PG:** * **Current Global Target:** The "3 by 5" target has been succeeded by the **95-95-95 target** (by 2030): 95% of people living with HIV know their status, 95% of those diagnosed receive ART, and 95% of those on ART achieve viral suppression. * **ART in India:** Under the National AIDS Control Programme (NACP), ART is provided free of cost. The current policy is **"Treat All,"** meaning ART is started regardless of CD4 count or clinical stage immediately upon diagnosis. * **First-line Regimen (Adults):** The preferred first-line regimen in India is now **TLD** (Tenofovir + Lamivudine + Dolutegravir).

Question 28: A negative Mantoux test is indicated by an induration measuring less than what diameter?

A. 10 mm
B. 15 mm
C. 20 mm
D. 5 mm (Correct Answer)

Explanation: **Explanation:** The Mantoux test (Tuberculin Skin Test) is a screening tool for *Mycobacterium tuberculosis* infection. It involves the intradermal injection of 0.1 ml of 5 TU (Tuberculin Units) of Purified Protein Derivative (PPD). The result is read 48–72 hours later by measuring the **diameter of induration** (palpable hardening), not erythema. **1. Why 5 mm is the correct answer:** According to standard diagnostic criteria (including WHO and RNTCP/NTEP guidelines), an induration of **less than 5 mm** is considered a **negative** result. It indicates that the individual has likely not been infected with TB or has a suppressed immune response. **2. Analysis of Incorrect Options:** * **10 mm (Option A):** This is the threshold for a **positive** result in "high-risk" groups, such as healthcare workers, residents of high-prevalence areas, or patients with clinical conditions like diabetes or silicosis. * **15 mm (Option B):** This is the threshold for a **positive** result in individuals with **no known risk factors** for TB. * **20 mm (Option C):** This is significantly higher than the standard diagnostic cut-off. An induration of this size often indicates a strong positive reaction or a "vesicular" reaction, suggesting a high likelihood of active infection or extreme sensitivity. **3. High-Yield Clinical Pearls for NEET-PG:** * **False Negatives:** Can occur in miliary TB, malnutrition, HIV/AIDS (due to anergy), and recent viral infections (e.g., Measles). * **False Positives:** Can occur due to prior **BCG vaccination** or infection with Non-Tuberculous Mycobacteria (NTM). * **HIV Patients:** In HIV-positive individuals, an induration of **≥ 5 mm** is considered positive due to their compromised immune status. * **Reading:** Always measure the transverse diameter of the induration using the "pen method."

Question 29: What is the Category II treatment for tuberculosis?

A. 2HRZES (Correct Answer)
B. 1HRZE
C. 5HRZ
D. None

Explanation: ### Explanation **Concept:** Under the Revised National Tuberculosis Control Programme (RNTCP), Category II was historically designed for **previously treated cases** (Relapse, Treatment after Failure, and Treatment After Loss to Follow-up). The goal was to provide a more intensive regimen to combat potential drug resistance. **Why 2HRZES is Correct:** The Category II regimen consisted of an **Intensive Phase (IP)** lasting 3 months and a **Continuation Phase (CP)** lasting 5 months. * **2HRZES:** During the first 2 months of the IP, five drugs were given: Isoniazid (H), Rifampicin (R), Pyrazinamide (Z), Ethambutol (E), and an injection of Streptomycin (S). * This was followed by 1 month of **HRZE** (without Streptomycin) and 5 months of **HRE** (CP). **Analysis of Incorrect Options:** * **B (1HRZE):** This represents only the third month of the Intensive Phase in Category II, not the entire regimen. * **C (5HRZ):** This does not follow any standard RNTCP protocol. The Continuation Phase for Category II was actually 5HRE. **High-Yield Clinical Pearls for NEET-PG:** 1. **Current Status:** As per the latest **National Strategic Plan (NSP)** and WHO guidelines, the distinction between Category I and Category II has been **abolished**. 2. **Universal Drug Susceptibility Testing (UDST):** All patients are now screened for Rifampicin resistance at the time of diagnosis. 3. **Current Protocol:** "Previously treated" patients are no longer given Streptomycin (Category II). Instead, if they are drug-sensitive, they receive the same 6-month regimen as new cases (2HRZE / 4HRE). If drug-resistant, they are put on specific MDR-TB regimens. 4. **Drug Codes:** H (Isoniazid), R (Rifampicin), Z (Pyrazinamide), E (Ethambutol), S (Streptomycin).

Question 30: Which of the following conditions does NOT require isolation?

A. Mumps
B. Measles
C. Hepatitis A
D. Pneumonic plague (Correct Answer)

Explanation: ### Explanation The correct answer is **D. Pneumonic plague**. **1. Why Pneumonic Plague is the correct answer:** In the context of standard public health practices and infectious disease management, **Pneumonic Plague** is a highly contagious, fatal disease that requires **strict quarantine**, not just simple isolation. * **Isolation** refers to the separation of *ill* persons with a contagious disease from those who are healthy. * **Quarantine** refers to the restriction of movement of *healthy* persons who have been exposed to a communicable disease during its incubation period. Under International Health Regulations (IHR), Pneumonic Plague is one of the three internationally quarantinable diseases (along with Cholera and Yellow Fever). Because of its rapid transmission via respiratory droplets and high mortality rate, it demands more rigorous containment measures than standard isolation. **2. Why the other options are incorrect:** * **A. Mumps:** Requires respiratory isolation for 5 days after the onset of parotid swelling to prevent droplet transmission. * **B. Measles:** Requires strict respiratory isolation from the onset of catarrhal symptoms until 4 days after the appearance of the rash. It is one of the most contagious vaccine-preventable diseases. * **C. Hepatitis A:** Requires enteric precautions (isolation of feces/blood) particularly for diapered or incontinent patients, especially during the first two weeks of illness or one week after the onset of jaundice. **3. NEET-PG High-Yield Clinical Pearls:** * **Quarantinable Diseases (Old WHO list):** Cholera, Plague (Pneumonic), and Yellow Fever. * **Incubation Period of Plague:** 1–7 days (Pneumonic is usually 1–3 days). * **Drug of Choice for Plague:** Streptomycin (Treatment); Doxycycline (Chemoprophylaxis). * **Vector for Plague:** Oriental rat flea (*Xenopsylla cheopis*). * **Key Distinction:** Isolation is for the **Sick**; Quarantine is for the **Healthy/Exposed**.

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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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