Infectious Diseases Practice Questions

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.

Q: A two-year-old unimmunized child presents with fever for 5 days and a rash behind the ear that appeared the day before presentation. The child also has a running nose and congested eyes. What is the most probable diagnosis?

Measles. **Explanation:** The clinical presentation is classic for **Measles (Rubeola)**. The diagnosis is based on the following high-yield features: 1. **Prodromal Phase:** Fever, rhinorrhea (running nose), and conjunctivitis (congested eyes) are the hallmark "3 Cs" (Cough, Coryza, Conjunctivitis). 2. **Rash Progression:** The rash in measles typically appears on the 4th or 5th day of fever. It is a maculopapular rash that characteristically starts **behind the ears** (at the hairline) and spreads cephalocaudally (downward) to the face, trunk, and extremities. 3. **Immunization Status:** Being "unimmunized" is a significant risk factor, as the first dose of the MR/MMR vaccine is typically given at 9 months. **Why other options are incorrect:** * **Rubella (German Measles):** While the rash also spreads downward, the prodrome is much milder (low-grade fever), and the most characteristic finding is **post-auricular/suboccipital lymphadenopathy**, not severe coryza. * **Mumps:** This primarily presents with painful swelling of the **parotid glands**, not a maculopapular rash. * **Chickenpox (Varicella):** The rash is **pleomorphic** (vesicles, pustules, and scabs present simultaneously) and typically starts on the trunk ("centripetal" distribution), appearing in crops. **NEET-PG High-Yield Pearls:** * **Koplik Spots:** Pathognomonic for measles; seen on the buccal mucosa opposite the lower 2nd molar *before* the rash appears. * **Vitamin A:** Supplementation is mandatory in all children with measles to prevent complications like blindness and pneumonia. * **Infectivity:** Most infectious during the prodromal stage (4 days before to 4 days after the appearance of the rash). * **Subacute Sclerosing Panencephalitis (SSPE):** A rare, delayed neurological complication occurring years after the initial infection.

Q: Massive myoclonus is a hallmark of which stage of Subacute Sclerosing Panencephalitis (SSPE)?

Stage 2. Subacute Sclerosing Panencephalitis (SSPE) is a progressive, fatal neurodegenerative disease caused by a persistent infection with a mutant Measles virus. The clinical progression is classically divided into four stages [1]: * **Stage 1 (Behavioral):** Characterized by subtle changes including irritability, social withdrawal, and declining school performance. * **Stage 2 (Motor Regression):** This is the stage where **massive myoclonus** (periodic, synchronous muscle jerks) occurs. It is the hallmark of this stage, often accompanied by worsening motor coordination and seizures. * **Stage 3 (Extrapyramidal):** Myoclonus disappears and is replaced by severe extrapyramidal symptoms, including choreoathetosis, dystonia, and spasticity. * **Stage 4 (Terminal):** The patient enters a vegetative state, characterized by akinetic mutism, decorticate/decerebrate rigidity, and eventually death. **Why Stage 2 is correct:** Massive myoclonus is the defining clinical feature of Stage 2. These jerks are typically "slow," lasting 1–3 seconds, and involve the head, trunk, and limbs. **High-Yield Clinical Pearls for NEET-PG:** * **EEG Finding:** Characterized by **Radermecker complexes** (periodic, high-voltage, generalized slow-wave complexes). * **Diagnosis:** Elevated titers of **anti-measles antibodies** in both serum and CSF (intrathecal synthesis) [1]. * **CSF Analysis:** Shows a normal cell count but significantly elevated **gamma globulin** levels (oligoclonal bands). * **Risk Factor:** Early-age measles infection (usually <2 years old) with a latency period of 5–10 years.

Question 1

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 2

Which of the following is NOT a complication of chickenpox?

Accepted Answer

Pancreatitis

Answer

Pneumonia

Answer

Encephalitis

Answer

Thrombocytopenia

Question 3

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 4

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 5

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 6

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

Question 7

What is true regarding Lymphocytic interstitial pneumonitis (LIP)?

Accepted Answer

May be associated with hepatosplenomegaly

Answer

Is common in vertically acquired HIV infection

Answer

Is due to a protozoal infection

Answer

Is seen on chest X-ray as a perihilar infiltration in a butterfly distribution

Question 8

A two-year-old unimmunized child presents with fever for 5 days and a rash behind the ear that appeared the day before presentation. The child also has a running nose and congested eyes. What is the most probable diagnosis?

Accepted Answer

Measles

Answer

Rubella

Answer

Mumps

Answer

Chickenpox

Question 9

Which of the following findings is LEAST suggestive of poliovirus infection?

Accepted Answer

Descending motor paralysis with preservation of tendon reflexes and sensation

Answer

Low grade fever and malaise with complete resolution in 2 to 3 days

Answer

Biphasic illness with several days of fever, then meningeal symptoms and asymmetric flaccid paralysis 5 to 10 days later

Answer

Failure to isolate a virus from the cerebrospinal fluid in the presence of marked meningismus

Question 10

Massive myoclonus is a hallmark of which stage of Subacute Sclerosing Panencephalitis (SSPE)?

Accepted Answer

Stage 2

Answer

Stage 1

Answer

Stage 3

Answer

Stage 4

Infectious Diseases — MCQs

Infectious Diseases — MCQs

On this page

Practice by Chapter

Want unlimited practice?