Infectious Diseases Practice Questions

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).

Q: What is the percentage of coincidence between a sore throat and acute rheumatic fever?

3%. **Explanation:** Acute Rheumatic Fever (ARF) is a delayed, non-suppurative sequela of an upper respiratory tract infection caused by **Group A Beta-Hemolytic Streptococcus (GABHS)**. The relationship between the initial infection and the development of ARF is a classic high-yield concept in Pediatrics. **1. Why 3% is Correct:** Epidemiological studies have established that in an **untreated** or inadequately treated episode of GABHS pharyngitis (sore throat), approximately **3%** of individuals will go on to develop Acute Rheumatic Fever. This percentage remains the gold standard in medical literature for endemic populations. In contrast, during "sporadic" outbreaks in developed nations, the incidence may drop significantly below 1%, but for examination purposes, the 3% rule is the recognized benchmark. **2. Analysis of Incorrect Options:** * **5%, 7%, and 9%:** These values overestimate the attack rate. While GABHS is a common cause of sore throat, the progression to ARF requires a specific combination of host genetic susceptibility and the rheumatogenic potential of the specific streptococcal strain (e.g., M-types 1, 3, 5, 6, 18). **3. Clinical Pearls for NEET-PG:** * **The Latent Period:** ARF typically develops **2–4 weeks** after the initial sore throat. * **Prevention:** Primary prevention (treating the sore throat with Penicillin within 9 days of onset) can almost entirely prevent the development of ARF. * **Skin Infections:** Unlike Post-Streptococcal Glomerulonephritis (PSGN), **ARF does not follow streptococcal skin infections (impetigo/pyoderma).** It only follows pharyngeal infections. * **Diagnosis:** Diagnosis is clinical, based on the **Revised Jones Criteria (2015)**, which now categorizes patients into low-risk and moderate/high-risk populations.

Q: What is the standard treatment for Chlamydia pneumoniae infection?

Erythromycin. **Explanation:** *Chlamydia pneumoniae* is an obligate intracellular bacterium and a common cause of atypical pneumonia in children and adolescents. Because it lacks a traditional peptidoglycan cell wall, it is inherently resistant to beta-lactam antibiotics. **Why Erythromycin is correct:** Macrolides, such as **Erythromycin**, are the treatment of choice for *Chlamydia* species. They work by inhibiting protein synthesis by binding to the 50S ribosomal subunit. In pediatric practice, while Erythromycin is the classic answer, newer macrolides like Azithromycin or Clarithromycin are often preferred due to better GI tolerance and simpler dosing schedules. For older children (>8 years), Tetracyclines (Doxycycline) are also an effective alternative. **Why the other options are incorrect:** * **Ceftriaxone (Cephalosporin) & Penicillin:** These are beta-lactam antibiotics that act by inhibiting cell wall synthesis. Since *Chlamydia* does not have a typical bacterial cell wall, these drugs are completely ineffective. * **Sulphonamides:** While sulfonamides interfere with folic acid synthesis and are used for some intracellular organisms (like *Nocardia*), they are not the standard of care for *Chlamydia pneumoniae* and show poor clinical efficacy compared to macrolides. **High-Yield Clinical Pearls for NEET-PG:** * **Atypical Presentation:** Look for a "subacute" onset with a prominent, non-productive cough, low-grade fever, and "dissociation" (physical signs on chest X-ray are much worse than the clinical appearance of the patient). * **Chlamydia trachomatis (Infants):** Causes "staccato cough" and peripheral eosinophilia in neonates (usually 2–12 weeks old). Erythromycin is also the drug of choice here. * **Drug Side Effect:** Be aware that Erythromycin use in neonates is associated with an increased risk of **Infantile Hypertrophic Pyloric Stenosis (IHPS)**.

Question 1

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 2

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 3

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 4

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

Accepted Answer

Lymphadenopathy

Answer

Retropharyngeal abscess

Answer

Laryngeal edema

Answer

Cellulitis

Question 5

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 6

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

Question 7

What is the percentage of coincidence between a sore throat and acute rheumatic fever?

Accepted Answer

3%

Answer

5%

Answer

7%

Answer

9%

Question 8

What is the standard treatment for Chlamydia pneumoniae infection?

Accepted Answer

Erythromycin

Answer

Ceftriaxone

Answer

Penicillin

Answer

Sulphonamide

Question 9

A 5-year-old child developed seizures a few months ago. The seizures start with a strange smell (burning rubber), continue with generalized contractions, and end with rhythmic spasms. Consciousness is lost during attacks, and the child is confused afterwards. The child was prescribed phenytoin as the initial treatment. Currently, the parents bring the child for scheduled DTP immunization (diphtheria, tetanus, pertussis). Which of the following is the most appropriate next step in management?

Accepted Answer

Deferral of DTP immunization.

Answer

Immunization with DTP vaccine.

Answer

Change medication to phenobarbital and DTP immunization.

Answer

Two weeks drug holiday and DTP immunization afterwards.

Question 10

Which is the most common organism causing congenital pneumonia?

Accepted Answer

Group B Streptococcus

Answer

Escherichia coli

Answer

Staphylococcus aureus

Answer

Salmonella spp.

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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