Infectious Diseases Practice Questions

Q: What is the recommended dose of oseltamivir for chemoprophylaxis in an infant?

3 mg/kg once daily. **Explanation:** The correct answer is **A. 3 mg/kg once daily**. **Medical Concept:** Oseltamivir is a neuraminidase inhibitor used for both the treatment and chemoprophylaxis of Influenza A and B. In infants (aged 0–12 months), the dosing is weight-based rather than age-based due to the rapid physiological changes in renal clearance during the first year of life. For **chemoprophylaxis**, the standard recommendation is **3 mg/kg administered once daily** for 7–10 days following exposure. **Analysis of Options:** * **Option A (Correct):** 3 mg/kg once daily is the established prophylactic dose for infants to prevent the onset of symptoms after exposure. * **Option B, C, and D (Incorrect):** These options provide fixed doses (20 mg). While 30 mg, 45 mg, 60 mg, and 75 mg are standard fixed doses for older children and adults based on weight bands, infants require precise mg/kg dosing. Furthermore, "thrice a day" (Option D) is never a standard frequency for oseltamivir, which is typically dosed once daily (prophylaxis) or twice daily (treatment). **High-Yield Clinical Pearls for NEET-PG:** * **Treatment vs. Prophylaxis:** For infants, the **treatment** dose is 3 mg/kg **twice daily** for 5 days, whereas **prophylaxis** is **once daily**. * **Age Limit:** Oseltamivir is FDA-approved for treatment from birth and for prophylaxis from 3 months of age (though used off-label in younger infants during outbreaks). * **Mechanism of Action:** It inhibits the neuraminidase enzyme, preventing the release of new virions from infected host cells. * **Timing:** To be most effective, oseltamivir should be started within **48 hours** of symptom onset or exposure.

Q: A 9-month-old child has been diagnosed with measles. What is the recommended dose of vitamin A administration?

1,00,000 IU. **Explanation:** Vitamin A is a critical micronutrient for maintaining epithelial integrity and immune function. In the context of **Measles**, Vitamin A levels drop rapidly, increasing the risk of severe complications like blindness (keratomalacia), pneumonia, and diarrhea. Therefore, the WHO and National Guidelines recommend immediate supplementation for all children diagnosed with measles. The dosage is strictly **age-dependent**: * **< 6 months:** 50,000 IU * **6 – 11 months:** 1,00,000 IU (Correct Answer) * **≥ 12 months:** 2,00,000 IU **Analysis of Options:** * **Option A (50,000 IU):** This is the therapeutic dose for infants younger than 6 months. * **Option B (1,00,000 IU):** Correct. Since the child is 9 months old, they fall into the 6–11 month bracket. * **Option C (1,50,000 IU):** This is not a standard recommended dose in the Vitamin A protocol. * **Option D (2,00,000 IU):** This is the dose for children aged 1 year and older. **High-Yield Clinical Pearls for NEET-PG:** 1. **Schedule:** For measles treatment, two doses are given: the first immediately upon diagnosis and the second the following day. A third dose is added 4 weeks later if clinical signs of Vitamin A deficiency (e.g., Bitot’s spots) are present. 2. **Prophylaxis vs. Treatment:** Do not confuse this with the **National Prophylactic Program**, where the first dose (1 lakh IU) is given at 9 months (with Measles-Rubella vaccine) and subsequent doses (2 lakh IU) are given every 6 months until age 5 (total 9 doses/17 lakh IU). 3. **Mechanism:** Vitamin A reduces measles mortality by approximately 50%.

Q: A child's CSF was examined and showed slightly raised or normal PMN cells, raised lymphocytes, absence of mycotic growth, normal or above normal protein value, and normal glucose level. What is the most probable diagnosis?

Viral meningitis. ### Explanation The clinical presentation of cerebrospinal fluid (CSF) analysis is a high-yield topic for NEET-PG. The diagnosis of **Viral Meningitis** (Aseptic Meningitis) is based on the following characteristic CSF findings: 1. **Glucose Level:** This is the most critical differentiator. In viral meningitis, glucose is **normal** (typically >2/3rd of blood glucose), whereas it is significantly decreased in bacterial, fungal, and tuberculous meningitis. 2. **Cellular Profile:** There is a predominance of **lymphocytes**. While PMNs (polymorphonuclear cells) may be slightly raised in the very early stages (first 24 hours), the shift to lymphocytosis is classic. 3. **Protein:** Protein levels are usually **normal or mildly elevated** (typically <100 mg/dL), unlike the marked elevations seen in other types. #### Why the other options are incorrect: * **Pyogenic Bacterial Meningitis:** Characterized by marked **neutrophilic pleocytosis**, significantly **low glucose** (<40 mg/dL), and very high protein levels. * **Tuberculous Meningitis (TBM):** While it shows lymphocytosis, the **glucose is always low** and the protein is characteristically very high (often causing a cobweb coagulum). * **Fungal Meningitis:** Similar to TBM, it presents with low glucose and elevated protein. The question also specifically mentions the **absence of mycotic growth**. #### NEET-PG High-Yield Pearls: * **Most common cause of Viral Meningitis:** Enteroviruses (Coxsackie and Echovirus). * **Normal CSF Glucose:** 40–70 mg/dL (or 60-70% of plasma glucose). * **Normal CSF Protein:** 15–45 mg/dL. * **Mnemonic for TBM:** "Low Sugar, High Protein, Lymphocytes" (The "T" in TBM stands for "Tiny sugar").

Q: Mumps is characterized by a triad of which of the following?

Epidemic parotitis, orchitis-oophoritis, pancreatitis.. **Explanation:** Mumps is an acute viral infection caused by the **Rubulavirus** (Paramyxoviridae family). It is characterized by its affinity for glandular and neurological tissues. The classic clinical triad of Mumps consists of **Epidemic parotitis, Orchitis/Oophoritis, and Pancreatitis**. 1. **Why Option A is correct:** The virus primarily replicates in the upper respiratory tract and then spreads hematogenously to target organs. * **Parotitis:** The most common manifestation (95% of symptomatic cases), usually bilateral. * **Orchitis/Oophoritis:** The most common extra-salivary site in post-pubertal males (orchitis is usually unilateral). * **Pancreatitis:** Presents as epigastric pain and vomiting; it is a classic component of the triad, though often mild. 2. **Why other options are incorrect:** * **Option B & C:** While **Meningoencephalitis** is the most common *neurological* complication of Mumps (often presenting as aseptic meningitis), it is not traditionally considered part of the "triad" of glandular involvement that defines the classic presentation in medical literature and competitive exams. **High-Yield Clinical Pearls for NEET-PG:** * **Incubation Period:** 14–21 days (Average 18 days). * **Infectivity:** Maximum 48 hours *before* the onset of parotitis. * **Diagnosis:** Primarily clinical; however, **Serum Amylase** is elevated in both parotitis and pancreatitis. * **Complications:** * Most common complication in children: **Aseptic meningitis**. * Most common cause of **acquired sensorineural deafness** in children (usually unilateral). * **Prevention:** Live attenuated vaccine (Jeryl Lynn strain) as part of the MMR vaccine.

Q: Which of the following is NOT a complication of chickenpox?

Pancreatitis. **Explanation:** Chickenpox, caused by the **Varicella-Zoster Virus (VZV)**, is typically a self-limiting childhood illness but can lead to several systemic complications, especially in adults and immunocompromised individuals. **Why Pancreatitis is the Correct Answer:** Pancreatitis is **not** a recognized or classic complication of primary Varicella infection. While VZV can affect multiple organ systems, the pancreas is rarely, if ever, a target during the acute phase of chickenpox. In contrast, pancreatitis is a well-known complication of other viral infections like **Mumps** and **Coxsackievirus B**. **Analysis of Incorrect Options:** * **Pneumonia:** This is the **most serious complication** of chickenpox in adults. It typically presents 3–5 days into the illness with cough and dyspnea. * **Encephalitis:** Neurological complications are well-documented. In children, **Acute Cerebellar Ataxia** (presenting with nystagmus and ataxia) is more common, while diffuse **Encephalitis** is more frequent in adults. * **Thrombocytopenia:** Hematological issues, including transient thrombocytopenia and purpura fulminans, can occur due to viral interference with platelet production or immune-mediated destruction. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication in children:** Secondary bacterial infection of skin lesions (usually *Staph. aureus* or *Strep. pyogenes*). * **Reye’s Syndrome:** A serious complication involving encephalopathy and liver failure, linked to **Aspirin** use during chickenpox. * **Congenital Varicella Syndrome:** Occurs if the mother is infected in the first 20 weeks of pregnancy; characterized by cicatricial skin scarring, limb hypoplasia, and chorioretinitis. * **Tzanck Smear:** Shows **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusion bodies.

Q: Malnourished children are at increased risk for complications of measles, leading to greater morbidity and mortality. Which of the following vitamins should be administered to these children to reduce these risks?

Vitamin A. **Explanation:** **1. Why Vitamin A is the Correct Answer:** Measles virus significantly depletes Vitamin A stores in the body, leading to a state of "secondary deficiency." Vitamin A is essential for maintaining the integrity of epithelial surfaces (respiratory, intestinal, and ocular) and for the proper functioning of the immune system. In malnourished children, this deficiency impairs the body's ability to regenerate damaged mucosal barriers, leading to severe complications such as **blindness (keratomalacia)**, **severe pneumonia**, and **croup**. The World Health Organization (WHO) recommends Vitamin A supplementation for all children with acute measles. It has been clinically proven to reduce the severity of the disease, decrease the risk of secondary infections, and significantly lower the mortality rate. **2. Why Other Options are Incorrect:** * **Vitamin B:** While B-complex vitamins are essential for metabolism, they do not play a specific role in the pathogenesis or recovery of measles-related mucosal damage. * **Vitamin C:** Although an antioxidant that supports general immunity, there is no evidence that Vitamin C reduces the specific complications or mortality associated with measles. * **Vitamin D:** While important for bone health and general immune modulation, it is not the standard of care or the specific nutrient depleted during a measles infection. **3. High-Yield Clinical Pearls for NEET-PG:** * **Dosage:** Administer two doses, 24 hours apart: * < 6 months: 50,000 IU * 6–11 months: 100,000 IU * ≥ 12 months: 200,000 IU * **Koplik Spots:** Pathognomonic sign found on the buccal mucosa opposite the lower 2nd molars. * **SSPE (Subacute Sclerosing Panencephalitis):** The most dreaded late complication of measles, occurring years after the initial infection. * **Most Common Complication:** Otitis media. * **Most Common Cause of Death:** Pneumonia (Hecht’s Giant Cell Pneumonia).

Q: Which of the following is the least common complication of measles?

Subacute sclerosing panencephalitis (SSPE). **Explanation:** The correct answer is **D. Subacute sclerosing panencephalitis (SSPE)**. Measles is associated with several complications, ranging from very common to extremely rare. The distinction between these options lies in their **frequency vs. severity**. 1. **Why SSPE is the correct answer:** SSPE is a progressive, fatal neurodegenerative disease caused by a persistent infection with a mutant measles virus. While devastating, it is the **least common** complication, occurring in approximately **1 in 10,000 to 1 in 100,000** cases. It typically manifests 7–10 years after the initial measles infection. 2. **Why other options are incorrect:** * **Diarrhea (Option A):** This is the **most common** complication of measles overall (occurring in ~8% of cases), particularly in malnourished children. * **Otitis Media (Option C):** This is the most common **bacterial** complication of measles. * **Pneumonia (Option B):** This is the most common cause of **measles-related death** in children. It can be caused by the virus itself (Hecht’s giant cell pneumonia) or secondary bacterial infections. **NEET-PG High-Yield Pearls:** * **Most common complication:** Diarrhea. * **Most common cause of death:** Pneumonia. * **Most common CNS complication:** Post-measles encephalitis (1 in 1,000). * **Vitamin A:** Supplementation reduces mortality and the severity of complications (given as two doses 24 hours apart). * **SSPE Diagnosis:** Look for high titers of anti-measles antibodies in the CSF and characteristic **periodic complexes** on EEG.

Q: Which of the following is false regarding measles?

Nikolsky's sign. **Explanation:** The correct answer is **D. Nikolsky’s sign**. **Nikolsky’s sign** is a clinical finding where the top layers of the skin slip away from the lower layers when rubbed, indicating a loss of intercellular adhesion (acantholysis). This sign is characteristic of **Pemphigus vulgaris** and **Staphylococcal Scalded Skin Syndrome (SSSS)**. It is **not** a feature of measles, which is a viral exanthematous illness that does not involve bullae or skin sloughing. **Analysis of other options:** * **A. Koplik’s spots:** These are the pathognomonic sign of measles. They are small, bluish-white grains of sand on an erythematous base, typically found on the buccal mucosa opposite the lower second molars during the prodromal phase. * **B. Maculopapular skin rash:** This is the hallmark of the eruptive phase. The rash typically begins behind the ears at the hairline, spreads cranio-caudally (downward), and disappears in the same order, often leaving behind brownish discoloration or fine desquamation. * **C. Fever and malaise:** These are common prodromal symptoms. Measles is characterized by high-grade fever and the "3 Cs": Cough, Coryza, and Conjunctivitis. **High-Yield Clinical Pearls for NEET-PG:** * **Infectivity:** Most infectious during the prodromal period (4 days before to 4 days after the appearance of the rash). * **Vitamin A:** Supplementation is recommended for all children with measles to reduce the risk of complications like blindness and severe pneumonia. * **Subacute Sclerosing Panencephalitis (SSPE):** A rare, delayed, and fatal neurological complication occurring years after the initial infection. * **Modified Measles:** Occurs in partially immune individuals; the incubation period is longer, and symptoms are milder.

Q: At what age group is Streptococcal pneumoniae most commonly encountered?

Less than 5 years. **Explanation:** *Streptococcus pneumoniae* (Pneumococcus) is the most common bacterial cause of community-acquired pneumonia (CAP) across almost all pediatric age groups. However, its highest incidence and clinical burden are seen in children **less than 5 years of age**. **Why Option A is Correct:** In children under 5, the immune system is still developing, and there is a lack of protective antibodies against various pneumococcal serotypes. This age group also has the highest rates of nasopharyngeal colonization, which serves as a precursor to invasive diseases like pneumonia, meningitis, and bacteremia. Globally, *S. pneumoniae* is a leading cause of mortality in children under 5, particularly in developing countries. **Why Other Options are Incorrect:** * **Option B (5-15 years):** While *S. pneumoniae* still occurs, the relative incidence of atypical pathogens like *Mycoplasma pneumoniae* and *Chlamydophila pneumoniae* increases in school-aged children and adolescents. * **Options C & D (Adult groups):** While *S. pneumoniae* remains the most common cause of CAP in adults, the absolute frequency of infections and the risk of invasive disease are significantly lower compared to the vulnerable under-5 pediatric population (until reaching the geriatric age group, >65 years). **High-Yield Clinical Pearls for NEET-PG:** * **Most Common Cause:** *S. pneumoniae* is the #1 cause of bacterial pneumonia in children >3 weeks of age. * **Radiology:** Classically presents as **lobar pneumonia** with air bronchograms. * **Complication:** It is the most common cause of **empyema thoracis** in children. * **Prevention:** The **Pneumococcal Conjugate Vaccine (PCV13)** is part of the National Immunization Schedule (Universal Immunization Programme) in India, given at 6 weeks, 14 weeks, and a booster at 9 months.

Question 1

What is the recommended dose of oseltamivir for chemoprophylaxis in an infant?

Accepted Answer

3 mg/kg once daily

Answer

20 mg once a day

Answer

20 mg twice a day

Answer

20 mg thrice a day

Question 2

A 9-month-old child has been diagnosed with measles. What is the recommended dose of vitamin A administration?

Accepted Answer

1,00,000 IU

Answer

50,000 IU

Answer

1,50,000 IU

Answer

2,00,000 IU

Question 3

A child's CSF was examined and showed slightly raised or normal PMN cells, raised lymphocytes, absence of mycotic growth, normal or above normal protein value, and normal glucose level. What is the most probable diagnosis?

Accepted Answer

Viral meningitis

Answer

Pyogenic bacterial meningitis

Answer

Fungal meningitis

Answer

Tuberculous meningitis

Question 4

Mumps is characterized by a triad of which of the following?

Accepted Answer

Epidemic parotitis, orchitis-oophoritis, pancreatitis.

Answer

Orchitis-oophoritis, encephalitis, pancreatitis.

Answer

Epidemic parotitis, meningoencephalitis, pancreatitis.

Answer

None of the above.

Question 5

What is the ideal time for starting post-exposure prophylaxis with acyclovir in a person exposed to varicella?

Accepted Answer

7-9th day

Answer

Immediately after exposure

Answer

3rd day

Answer

10-14th day

Question 6

Which of the following is NOT a complication of chickenpox?

Accepted Answer

Pancreatitis

Answer

Pneumonia

Answer

Encephalitis

Answer

Thrombocytopenia

Question 7

Malnourished children are at increased risk for complications of measles, leading to greater morbidity and mortality. Which of the following vitamins should be administered to these children to reduce these risks?

Accepted Answer

Vitamin A

Answer

Vitamin B

Answer

Vitamin C

Answer

Vitamin D

Question 8

Which of the following is the least common complication of measles?

Accepted Answer

Subacute sclerosing panencephalitis (SSPE)

Answer

Diarrhea

Answer

Pneumonia

Answer

Otitis media

Question 9

Which of the following is false regarding measles?

Accepted Answer

Nikolsky's sign

Answer

Koplik's spots

Answer

Maculopapular skin rash

Answer

Fever and malaise

Question 10

At what age group is Streptococcal pneumoniae most commonly encountered?

Accepted Answer

Less than 5 years

Answer

5-15 years

Answer

20-25 years

Answer

30-40 years

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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