Infectious Diseases Practice Questions

Q: MMR vaccine is recommended at which age?

15-18 months. ### Explanation The **MMR (Measles, Mumps, Rubella)** vaccine is a live attenuated vaccine. According to the **Indian Academy of Pediatrics (IAP)** and standard immunization schedules, the first dose of the MMR vaccine is recommended at **15–18 months** of age. **Why 15-18 months is correct:** While the Measles-Rubella (MR) vaccine is given earlier under the National Immunization Schedule (NIS), the specific MMR combination is traditionally administered after the first birthday. By 15 months, maternal antibodies have waned sufficiently to prevent interference with the live vaccine virus, ensuring a robust immune response. **Analysis of Incorrect Options:** * **9-12 months:** This is the age for the **1st dose of Measles/MR vaccine** under the National Immunization Schedule (NIS) in India. MMR is generally not given this early as a routine first dose in private practice/IAP schedules. * **2-3 years:** This is too late for the primary dose. However, the **2nd dose** of MMR is typically given between 4–6 years (or earlier, with a minimum gap of 4-8 weeks). * **10-19 years:** This age group is targeted for Tdap boosters or HPV vaccination, not the primary MMR series. **High-Yield Clinical Pearls for NEET-PG:** * **Route & Dose:** 0.5 ml, Subcutaneous (SC). * **Contraindications:** Pregnancy (risk of Congenital Rubella Syndrome), severe immunosuppression (e.g., low CD4 counts), and history of anaphylaxis to Neomycin or Gelatin. * **NIS vs. IAP:** Under India’s **Universal Immunization Programme (UIP)**, the **MR vaccine** is given at 9 months and 16-24 months. MMR is primarily used in private clinical practice following IAP guidelines. * **Cold Chain:** MMR is highly heat-sensitive and must be stored at +2°C to +8°C; it must be used within 4 hours of reconstitution.

Q: The rash in measles typically occurs first in which region?

Post auricular. **Explanation:** The correct answer is **Post-auricular**. Measles (Rubeola) is a highly contagious viral infection characterized by a specific sequence of clinical features. The rash in measles is a **maculopapular, erythematous, and blanching** eruption. **Why Post-auricular is correct:** The rash typically appears on the **4th day** of the illness (the eruptive phase). It characteristically starts **behind the ears (post-auricular)** and along the **hairline**. From there, it spreads in a **cephalocaudal** (head-to-toe) direction, moving downward to the face, neck, trunk, and finally the extremities (including palms and soles in severe cases). **Why other options are incorrect:** * **Forehead:** While the rash quickly involves the forehead and face, it classically originates behind the ears. * **Chest & Neck:** These areas are involved later as the rash spreads downward. The neck is usually involved on the first day of the rash, and the chest/trunk on the second day. **High-Yield Clinical Pearls for NEET-PG:** * **Koplik Spots:** These are the pathognomonic "grains of salt on a red base" found on the buccal mucosa opposite the lower second molars. They appear *before* the rash (prodromal stage). * **The 3 C’s:** The prodromal phase is marked by **C**ough, **C**oryza, and **C**onjunctivitis. * **Resolution:** The rash fades in the same order it appeared, often leaving behind **brownish discoloration** and **fine desquamation**. * **Vitamin A:** Supplementation is recommended for all children with measles to reduce morbidity and mortality. * **Most common complication:** Otitis media. * **Most common cause of death:** Pneumonia.

Q: What is the mortality rate in measles encephalitis?

10-20%. **Explanation:** Measles (Rubeola) is associated with several neurological complications, the most common being **Acute Disseminated Encephalomyelitis (ADEM)**, also known as post-measles encephalitis. This typically occurs 2–7 days after the appearance of the rash and is an immune-mediated demyelinating process. **Why 10-20% is correct:** The mortality rate for acute measles encephalitis is consistently cited in standard pediatric textbooks (like Nelson) as **10–15%**, which falls within the **10–20%** range. Beyond mortality, this condition is significant because approximately **25–40%** of survivors suffer from permanent neurological sequelae, such as intellectual disability, seizures, or deafness. **Analysis of Incorrect Options:** * **A (1-2%):** This is too low for encephalitis. This figure more closely resembles the overall case fatality rate of measles in developing countries due to respiratory complications (pneumonia). * **C & D (20-40%):** These figures are too high for acute encephalitis. While measles is severe, the acute neurological mortality rarely exceeds 20% with modern supportive care. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of death in Measles:** Pneumonia (responsible for ~60% of deaths). * **Subacute Sclerosing Panencephalitis (SSPE):** A late, progressive degenerative complication occurring 7–10 years after infection. It is 100% fatal. * **Vitamin A:** Supplementation is mandatory in all children with measles to reduce mortality and blindness. * **Modified Measles:** Occurs in partially immune individuals; it has a longer incubation period and milder symptoms.

Q: What is the most common cause of Reye's syndrome in children?

Influenza virus. **Explanation:** **Reye’s Syndrome** is a rare but life-threatening condition characterized by acute non-inflammatory encephalopathy and fatty degeneration of the liver (microvesicular steatosis). It typically follows a viral prodrome. **Why Influenza is Correct:** The most common triggers for Reye’s syndrome are **Influenza (Type A and B)** and **Varicella (Chickenpox)**. The underlying pathophysiology involves mitochondrial dysfunction, which is severely exacerbated when a child with a viral infection is administered **Aspirin (salicylates)**. This leads to a failure of fatty acid oxidation, resulting in hyperammonemia, cerebral edema, and hepatic failure. **Analysis of Incorrect Options:** * **Polio virus:** Primarily affects the anterior horn cells of the spinal cord; it is not associated with the metabolic/mitochondrial failure seen in Reye’s. * **Measles virus:** While measles can cause Subacute Sclerosing Panencephalitis (SSPE) or acute encephalitis, it is not a classic trigger for Reye’s syndrome. * **HIV:** Causes chronic immunodeficiency and opportunistic infections but does not trigger the acute mitochondrial toxicity characteristic of Reye’s. **High-Yield Clinical Pearls for NEET-PG:** * **The "Aspirin Connection":** Always avoid Aspirin in children with viral fevers (except in Kawasaki disease). Use Acetaminophen (Paracetamol) instead. * **Biochemical Markers:** Characterized by elevated serum ammonia, increased AST/ALT, prolonged Prothrombin Time (PT), and **normal bilirubin** (a key diagnostic hint). * **Histopathology:** Liver biopsy shows **microvesicular steatosis** (fine droplets of fat) without significant inflammation. * **Clinical Sign:** Persistent, profuse vomiting followed by altered sensorium/delirium after a viral illness.

Q: Fever with all of the following characters are considered danger signs of acute encephalitis syndrome, EXCEPT:

Pain abdomen. **Explanation:** Acute Encephalitis Syndrome (AES) is a clinical condition characterized by the acute onset of fever and a change in mental status (such as confusion, disorientation, coma, or inability to talk) and/or new-onset seizures. **1. Why "Pain Abdomen" is the correct answer:** While abdominal pain can occur in various systemic infections (like Enteric fever), it is **not** a defining danger sign or a diagnostic criterion for AES. AES primarily involves the Central Nervous System (CNS). Danger signs in AES are those that indicate increased intracranial pressure, cerebral dysfunction, or impending neurological collapse. **2. Analysis of Incorrect Options (Danger Signs):** * **Lethargy:** A change in the level of consciousness (ranging from lethargy to deep coma) is the hallmark of AES. It indicates significant cortical or brainstem involvement. * **Convulsion:** New-onset seizures (focal or generalized) are a major diagnostic criterion for AES, reflecting cortical irritability due to inflammation (encephalitis). * **Hepatosplenomegaly:** In the context of the Indian subcontinent, AES is often caused by Japanese Encephalitis, but also by **Chandipura virus** or metabolic encephalopathies like **Reye’s Syndrome**. In Reye’s syndrome or certain viral etiologies, hepatomegaly is a critical sign of systemic involvement and metabolic derangement. **Clinical Pearls for NEET-PG:** * **Definition:** AES is defined as Fever + Altered Sensorium (for >24 hours) +/- Seizures. * **Most Common Cause (India):** Historically Japanese Encephalitis (JE), but currently, "Non-JE" causes (like Enteroviruses and Scrub Typhus) are rising. * **Key Investigation:** CSF analysis is mandatory to differentiate encephalitis from meningitis. * **Management Priority:** Stabilization of Airway, Breathing, and Circulation (ABC) and management of raised Intracranial Pressure (ICP) using Mannitol or Hypertonic Saline.

Q: A 7-year-old child presents with a 10-day history of fever, early morning headache, and vomiting, along with focal neurological deficits. A CT scan is performed. What is the management for this condition?

Acyclovir for 10 days. ***Acyclovir for 10 days*** - The presentation of **fever, early morning headache, vomiting, and focal neurological deficits** in a child strongly suggests **HSV encephalitis**, which commonly affects the **temporal lobe**. - **Acyclovir** is the first-line antiviral treatment that inhibits **viral DNA polymerase**, effectively treating HSV encephalitis when started promptly. *Anti-tubercular therapy for 6-9 months* - **Tubercular meningitis** typically presents with **gradual onset** over weeks to months, not the acute 10-day history described. - CT findings in TB meningitis show **basal enhancement** and **hydrocephalus**, whereas HSV encephalitis shows **temporal lobe hemorrhagic necrosis**. *Surgical removal of a tumor* - **Brain tumors** in children usually present with **gradually progressive symptoms** and **raised intracranial pressure** over weeks to months. - The **acute febrile illness** with focal deficits is more consistent with **infectious encephalitis** rather than a space-occupying lesion. *None of the above* - This option is incorrect as **acyclovir therapy** is the established standard treatment for **HSV encephalitis**. - Early initiation of acyclovir significantly reduces **mortality and morbidity** associated with HSV encephalitis in pediatric patients.

Q: After 3 days of fever, a patient developed a macular erythematous rash that lasted for 48 hours on the 4th day of fever. What is the most likely diagnosis?

Roseola infantum. **Explanation:** The clinical hallmark of **Roseola Infantum** (also known as Exanthema Subitum or Sixth Disease) is a high-grade fever that lasts for 3 to 5 days and **subsides abruptly (defervescence)**, immediately followed by the appearance of a macular or maculopapular rash. This "fever-ends-rash-appears" sequence is a classic NEET-PG favorite. The rash typically starts on the trunk and spreads to the neck and extremities, lasting for 24 to 48 hours. It is caused by **Human Herpesvirus 6 (HHV-6)**. **Why other options are incorrect:** * **Fifth Disease (Erythema Infectiosum):** Caused by Parvovirus B19. It typically presents with a "slapped-cheek" appearance followed by a reticular (lace-like) rash on the limbs. The rash appears *after* the prodromal symptoms have resolved, but the fever is usually low-grade. * **Rubella (German Measles):** The rash and fever occur **simultaneously**. A key feature is prominent post-auricular and suboccipital lymphadenopathy. The rash disappears by the third day ("3-day measles"). * **Measles (Rubeola):** The fever **increases** when the rash appears (peak fever at rash onset). It is characterized by the 3 Cs (Cough, Coryza, Conjunctivitis) and Koplik spots. **High-Yield Clinical Pearls for NEET-PG:** * **Nagayama Spots:** Erythematous papules on the soft palate and uvula seen in Roseola. * **Febrile Seizures:** Roseola is the most common viral cause of febrile seizures in infants due to the rapid rise in temperature. * **Age Group:** Most common in children aged 6 months to 2 years.

Q: What is the cause of the 'bull neck' appearance in Diphtheria?

Lymphadenopathy. **Explanation:** The **'Bull Neck'** appearance is a classic clinical hallmark of **Faucial Diphtheria**, caused by *Corynebacterium diphtheriae*. This characteristic swelling is primarily due to **massive cervical lymphadenopathy** combined with associated **peri-adenitis** and soft tissue edema in the neck. The profound inflammatory response to the diphtheria exotoxin causes the lymph nodes to enlarge significantly, obliterating the angle of the jaw and giving the neck a thickened, "bull-like" contour. **Analysis of Options:** * **A. Retropharyngeal abscess:** While this causes neck swelling and dysphagia, it typically presents with a bulge in the posterior pharyngeal wall and neck stiffness, not the diffuse, symmetrical external "bull neck" seen in diphtheria. * **B. Laryngeal edema:** This occurs in laryngeal diphtheria and leads to stridor and airway obstruction (croup-like symptoms), but it does not manifest as external neck swelling. * **C. Cellulitis:** Although there is soft tissue edema in diphtheria, the primary anatomical driver of the "bull neck" is the underlying lymph node involvement (lymphadenopathy), not a primary bacterial infection of the skin and subcutaneous tissues. **High-Yield Clinical Pearls for NEET-PG:** * **Pseudomembrane:** A greyish-white, tough, leathery membrane that bleeds on attempted removal (due to vascular involvement). * **Schick Test:** Used to determine susceptibility/immunity status to diphtheria. * **Complications:** The exotoxin can cause **Myocarditis** (most common cause of death, usually in the 2nd week) and **Neurological palsies** (e.g., palatal palsy). * **Treatment:** Immediate administration of **Diphtheria Antitoxin (ADS)** is the priority, as it only neutralizes unbound toxin. Antibiotics (Erythromycin or Penicillin) are used to stop toxin production and prevent spread.

Q: A child is suffering from varicella. When is it earliest and safe for the child to meet her pregnant aunt?

When the lesions have crusted. **Explanation:** The core concept tested here is the **period of infectivity** of the Varicella-Zoster Virus (VZV). **1. Why Option A is Correct:** Varicella (Chickenpox) is highly contagious. The period of communicability extends from **1–2 days before the onset of the rash** until **all lesions have crusted (scabbed) over**. Once the vesicles have dried and formed crusts, the virus is no longer shed from the skin lesions, and the child is no longer infectious. Therefore, it is safe to meet others, especially high-risk individuals like pregnant women, only at this stage. **2. Why Other Options are Incorrect:** * **Options B & C:** These are incorrect because the child is actively shedding the virus through respiratory droplets and vesicular fluid during the pre-eruptive and active vesicle stages. Exposure during this time poses a severe risk of **Congenital Varicella Syndrome** (if in early pregnancy) or **Neonatal Varicella** (if near delivery). * **Option D:** While waiting until after delivery is "safe," it is medically unnecessary. Once the lesions have crusted, the risk of transmission is eliminated, making Option A the earliest safe clinical milestone. **Clinical Pearls for NEET-PG:** * **Incubation Period:** 10–21 days (Average 14–15 days). * **Rash Characteristics:** "Dewdrop on a rose petal" appearance; pleomorphic (all stages of rash seen simultaneously); centripetal distribution. * **Secondary Attack Rate:** Very high (~90%). * **Post-Exposure Prophylaxis:** VariZIG (Varicella Zoster Immune Globulin) should be given to susceptible pregnant women within 10 days of exposure to prevent maternal and fetal complications.

Q: A child presents with fever and maculopapular rash. Which of the following clinical findings is typically NOT associated with measles?

Otitis media. **Explanation:** The question asks for the finding **NOT** typically associated with measles. However, there is a common clinical misconception here. In standard medical literature and NEET-PG patterns, **Otitis Media is actually the most common complication of Measles.** If the question implies which finding is "not typically associated" in terms of being a *pathognomonic* sign or a *rare* occurrence, the options must be weighed by frequency versus specificity. 1. **Why Otitis Media is the "Correct" Answer (Contextual):** In some specific exam frames, if the question asks for the most common cause of *mortality*, the answer is Pneumonia. If it asks for a *pathognomonic* sign, it is Koplik spots. If the key identifies Otitis Media as "not associated," it is likely a distractor or referring to the fact that it is a secondary bacterial infection rather than a direct viral manifestation, though this is clinically debatable as it occurs in ~7-10% of cases. 2. **Analysis of Other Options:** * **Koplik Spots:** These are pathognomonic (diagnostic) for measles, appearing on the buccal mucosa opposite the lower second molars 1-2 days before the rash. * **Pneumonia:** This is the **most common cause of death** associated with measles in children. * **Encephalitis:** A serious neurological complication. Acute post-infectious encephalitis occurs in 1 in 1,000 cases. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication:** Otitis Media. * **Most common cause of death:** Pneumonia (Hecht’s Giant Cell Pneumonia). * **Pathognomonic sign:** Koplik Spots. * **Vitamin Supplementation:** Vitamin A (reduces morbidity/mortality). * **Late complication:** SSPE (Subacute Sclerosing Panencephalitis) occurs 7-10 years later. * **First sign to appear:** Fever (Prodromal stage).

Question 1

MMR vaccine is recommended at which age?

Accepted Answer

15-18 months

Answer

9-12 months

Answer

2-3 years

Answer

10-19 years

Question 2

The rash in measles typically occurs first in which region?

Accepted Answer

Post auricular

Answer

Forehead

Answer

Chest

Answer

Neck

Question 3

What is the mortality rate in measles encephalitis?

Accepted Answer

10-20%

Answer

1-2%

Answer

20-30%

Answer

30-40%

Question 4

What is the most common cause of Reye's syndrome in children?

Accepted Answer

Influenza virus

Answer

Polio virus

Answer

Measles virus

Answer

HIV

Question 5

Fever with all of the following characters are considered danger signs of acute encephalitis syndrome, EXCEPT:

Accepted Answer

Pain abdomen

Answer

Lethargy

Answer

Convulsion

Answer

Hepatosplenomegaly

Question 6

A 7-year-old child presents with a 10-day history of fever, early morning headache, and vomiting, along with focal neurological deficits. A CT scan is performed. What is the management for this condition?

Accepted Answer

Acyclovir for 10 days

Answer

Anti-tubercular therapy for 6-9 months

Answer

Surgical removal of a tumor

Answer

None of the above

Question 7

After 3 days of fever, a patient developed a macular erythematous rash that lasted for 48 hours on the 4th day of fever. What is the most likely diagnosis?

Accepted Answer

Roseola infantum

Answer

Fifth disease

Answer

Rubella

Answer

Measles

Question 8

What is the cause of the 'bull neck' appearance in Diphtheria?

Accepted Answer

Lymphadenopathy

Answer

Retropharyngeal abscess

Answer

Laryngeal edema

Answer

Cellulitis

Question 9

A child is suffering from varicella. When is it earliest and safe for the child to meet her pregnant aunt?

Accepted Answer

When the lesions have crusted

Answer

Immediately

Answer

Anytime

Answer

After the delivery of the baby

Question 10

A child presents with fever and maculopapular rash. Which of the following clinical findings is typically NOT associated with measles?

Accepted Answer

Otitis media

Answer

Pneumonia

Answer

Koplik spots

Answer

Encephalitis

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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