Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 341: At what age is the MMR vaccination typically given?

A. Birth
B. 6 months
C. 1 year
D. 18 months (Correct Answer)

Explanation: **Explanation:** In the context of the National Immunization Schedule (NIS) in India, the **MMR (Measles, Mumps, Rubella)** vaccine is typically administered as a booster dose at **18 months** (specifically between 16–24 months). Under the current Universal Immunization Programme (UIP), the **MR (Measles-Rubella)** vaccine has replaced the standalone Measles vaccine, given as a first dose at 9 months and a second dose at 16–24 months. However, in private practice (IAP guidelines), the MMR vaccine is the standard. **Analysis of Options:** * **A. Birth:** Vaccines given at birth include BCG, OPV-0, and Hepatitis B. Live viral vaccines like MMR are not given at birth due to the presence of maternal antibodies which neutralize the vaccine virus. * **B. 6 months:** No MMR/MR vaccine is scheduled here. The earliest a Measles-containing vaccine is given is 6 months *only* during outbreaks (known as the "zero dose"), which does not count toward the primary series. * **C. 1 year:** While some international schedules start MMR at 12 months, the Indian NIS/IAP focus is on the 9-month and 16–24 month windows. * **D. 18 months (Correct):** This aligns with the second dose/booster recommendation in India to ensure long-term immunity and cover primary vaccine failures from the first dose. **High-Yield Clinical Pearls for NEET-PG:** * **Route:** MMR is administered **Subcutaneously (SC)**. * **Adverse Effect:** The most common side effect is a transient fever and rash occurring 7–10 days after vaccination. * **Contraindication:** It is a live vaccine; hence, it is contraindicated in **pregnancy** and **severely immunocompromised** patients. However, it *can* be given to asymptomatic HIV-infected children. * **Vitamin A:** Always remember that Vitamin A supplementation is co-administered with Measles-containing vaccines in the NIS to reduce complications.

Question 342: What is the most common cause of neonatal meningitis?

A. Staphylococcus
B. E. coli (Correct Answer)
C. H. influenzae
D. Pneumococcus

Explanation: **Explanation:** Neonatal meningitis (occurring within the first 28 days of life) is primarily caused by pathogens colonizing the maternal birth canal. Globally, the most common causative organisms are **Group B Streptococcus (GBS)** and **Escherichia coli (E. coli)**. In the context of the Indian subcontinent and many NEET-PG clinical scenarios, **Gram-negative bacilli**, specifically **E. coli**, are frequently cited as the leading cause of neonatal meningitis and sepsis. E. coli possesses the **K1 capsular antigen**, which allows it to evade host immune responses and cross the blood-brain barrier effectively. **Analysis of Options:** * **B. E. coli (Correct):** It is the most common Gram-negative cause and a leading cause overall in the neonatal period. * **A. Staphylococcus:** While *S. aureus* or *Coagulase-negative Staphylococci (CONS)* can cause late-onset sepsis in NICU settings (especially with indwelling catheters), they are not the most common cause of primary meningitis. * **C. H. influenzae:** This was a leading cause in children aged 3 months to 5 years but has significantly declined due to the Hib vaccine. It is rare in the neonatal period. * **D. Pneumococcus (*S. pneumoniae*):** This is the most common cause of bacterial meningitis in infants **older than 3 months**, children, and adults, but not in neonates. **High-Yield Pearls for NEET-PG:** 1. **Age-wise Etiology:** * 0–28 days: GBS, E. coli, Listeria. * 3 months–5 years: *S. pneumoniae*, *N. meningitidis*. 2. **Listeria monocytogenes:** A notable cause of neonatal meningitis associated with maternal consumption of unpasteurized milk/cheese; it is inherently resistant to cephalosporins (requires Ampicillin). 3. **Clinical Presentation:** Neonatal meningitis often presents with non-specific signs like bulging fontanelle, temperature instability, refusal to feed, or seizures. 4. **CSF Findings:** High protein, low glucose, and pleocytosis (increased WBCs).

Question 343: What is true about polio?

A. Paralytic polio is the most common form.
B. Spastic paralysis is a characteristic symptom.
C. Intramuscular injections and increased muscular activity can lead to increased paralysis. (Correct Answer)
D. Polio drops used in pulse polio immunisation are given only to children under 3 years of age.

Explanation: **Explanation:** **1. Why Option C is Correct:** This phenomenon is known as **"Provocation Paralysis."** During the prodromal phase of a poliovirus infection, any trauma to the muscles—most commonly via **intramuscular (IM) injections**—or excessive physical exertion can lead to the localization of paralysis in that specific limb. The trauma causes increased vascularity and retrograde axonal transport of the virus from the peripheral nerves to the corresponding segment of the spinal cord, significantly increasing the risk of paralytic disease. **2. Why the Other Options are Incorrect:** * **Option A:** Inapparent (asymptomatic) infection is the most common form, occurring in over 90–95% of cases. Paralytic polio is the rarest form, occurring in less than 1% of infections. * **Option B:** Polio causes **Lower Motor Neuron (LMN)** type paralysis, characterized by **flaccid paralysis**, loss of deep tendon reflexes, and muscle atrophy. Spastic paralysis is a feature of Upper Motor Neuron (UMN) lesions. * **Option D:** Under the Pulse Polio Immunization (PPI) program in India, Oral Polio Vaccine (OPV) drops are administered to all children **under 5 years of age**, regardless of their previous immunization status. **High-Yield Clinical Pearls for NEET-PG:** * **Agent:** RNA Enterovirus (Picornaviridae family). Type 1 is the most common cause of epidemics. * **Transmission:** Fecal-oral route (most common). * **Clinical Sign:** "Tripod Sign" (child sits with hands behind for support due to spinal stiffness). * **CSF Findings:** Albuminocytologic dissociation is NOT seen (unlike Guillain-Barré Syndrome). * **VAPP vs VDPV:** Vaccine-Associated Paralytic Polio (VAPP) occurs in the vaccine recipient; Vaccine-Derived Poliovirus (VDPV) is due to the circulation of the mutated vaccine virus in the community.

Question 344: A mother brings her 9-month-old baby, concerned that no BCG scar has appeared, although the baby received the BCG vaccine at birth. What is the next best step?

A. Do the Mantoux test & wait for the result
B. Refer the baby for a chest X-ray & further evaluation
C. Give the BCG vaccine immediately
D. Reassure the mother (Correct Answer)

Explanation: ***Reassure the mother*** - The absence of a characteristic **BCG scar** up to 9 months later is common and does not indicate **vaccination failure** if the vaccine was properly administered and documented. - Standard vaccination protocols generally recommend **no re-vaccination** or immediate investigation solely based on the lack of a scar in an otherwise healthy infant. *Give the BCG vaccine immediately* - **Re-vaccination** without evidence of non-conversion (which is not routinely assessed) is not standard practice and carries the risk of increased **local adverse reactions**. - Current public health policies consider a single documented BCG dose adequate protection, regardless of the subsequent **cutaneous reaction**. *Do the Mantoux test & wait for the result* - The **Mantoux test (TST)** is not recommended solely for assessing BCG efficacy or scar absence in asymptomatic children due to difficulties in defining a protective threshold. - Finding a negative TST result does not currently mandate **re-vaccination**, as international guidelines prioritize coverage reliability over scar/TST status. *Refer the baby for a chest X-ray & further evaluation* - Extensive investigations, including a **chest X-ray**, are reserved for children presenting with signs or symptoms highly suggestive of **active tuberculosis disease**. - Performing aggressive workups on an asymptomatic child solely for an absent scar constitutes an excessive response and is not supported by clinical guidelines.

Question 345: A child was brought with c/o multiple lesions. O/E multiple vesicular lesions are seen on the palms, soles, and oral mucosa. Which of the following is the most likely etiological agent causing the disease?

A. Coxsackie virus (Correct Answer)
B. Varicella-zoster virus
C. Measles virus
D. Human-herpesvirus 6

Explanation: ***Coxsackie virus*** - The clinical presentation of vesicular lesions on the **palms**, **soles**, and **oral mucosa** is the classic triad for **Hand, Foot, and Mouth Disease (HFMD)**. - **Coxsackievirus A16** and **Enterovirus 71** are the most common causes of HFMD, a typically self-limiting illness in young children that spreads via fecal-oral or respiratory routes. *Varicella-zoster virus* - This virus causes **chickenpox**, which presents as a generalized, pruritic, vesicular rash in various stages of healing, typically starting on the **trunk** and spreading centrifugally. - The characteristic distribution of chickenpox is **centripetal**, and prominent involvement of palms and soles is uncommon. *Measles virus* - Measles presents with **maculopapular rash** that begins on the face and spreads cephalocaudally, accompanied by the **3 Cs** (cough, coryza, conjunctivitis) and **Koplik spots** on the buccal mucosa. - The rash is **not vesicular** and typically **spares the palms and soles**, unlike HFMD. *Human-herpesvirus 6* - HHV-6 is the cause of **roseola infantum** (exanthem subitum), characterized by a high fever that resolves, followed by a blanching **maculopapular rash** on the trunk. - Roseola does not cause vesicular lesions and characteristically **spares the palms and soles**.

Question 346: A neonate on examination has bilateral cataracts and, after investigations, is found to have a patent ductus arteriosus and salt and pepper retinopathy. What is the most likely congenital infection?

A. Varicella
B. Rubella (Correct Answer)
C. CMV
D. Toxoplasma

Explanation: ***Rubella***- The constellation of **bilateral cataracts**, **patent ductus arteriosus (PDA)**, and **salt and pepper retinopathy** is highly characteristic, if not pathognomonic, of **Congenital Rubella Syndrome (CRS)**.- Other common findings in CRS include **sensorineural hearing loss**, microcephaly, and **pulmonary artery stenosis**.*CMV*- Congenital Cytomegalovirus (CMV) infection is classically associated with **periventricular calcifications** on neuroimaging, microcephaly, and **sensorineural hearing loss**.- While CMV can cause chorioretinitis, it rarely causes the specific combination of **cataracts** and **PDA** found in this neonate, which strongly favors rubella.*Toxoplasma*- Congenital toxoplasmosis typically presents with the classic triad of **hydrocephalus**, **intracranial calcifications** (often random or diffuse), and focal **chorioretinitis**.- It is not typically associated with common cardiovascular defects like **PDA** or the specific appearance of **salt and pepper retinopathy**.*Varicella*- Congenital Varicella Syndrome is characterized by **skin scarring** (often a zigzag pattern), **limb hypoplasia**, and cortical atrophy.- Ocular findings usually involve **microphthalmia** and severe scarring rather than the specific combination of **cataracts** and **PDA**.

Question 347: A 5-year-old girl is brought to the clinic with a fever, cough, red eyes, running nose, and rash. The appearance of the child is shown below. What is the diagnosis? ![img-36.jpeg](img-36.jpeg)

A. Measles (Correct Answer)
B. Chickenpox
C. Mumps
D. Erythema infectiosum

Explanation: ***Measles*** - The clinical presentation of fever with the classic triad of **cough, coryza, and conjunctivitis** (the "3 Cs") is highly suggestive of measles (rubeola). - The image shows **Koplik's spots** (small white spots on the buccal mucosa), which are pathognomonic for measles and appear before the characteristic maculopapular rash. *Mumps* - Mumps is primarily characterized by **parotitis**, a painful swelling of the salivary glands, which is not described in this patient. - The classic prodrome of the "3 Cs" and Koplik's spots are absent in mumps. *Chickenpox* - The rash in chickenpox (varicella) is **vesicular**, often described as a "dewdrop on a rose petal," and appears in crops. This is different from the maculopapular rash of measles. - While a fever and malaise can occur, the prominent upper respiratory symptoms and conjunctivitis of measles are not typical of chickenpox. *Erythema infectiosum* - Caused by **Parvovirus B19**, this condition is characterized by a distinctive "**slapped-cheek**" rash on the face. - It is followed by a **lacy, reticular rash** on the trunk and extremities, which is inconsistent with the patient's presentation.

Question 348: An 8-year-old child presented with a sudden onset of high-grade fever, seizures, and loss of consciousness. On examination, the child had anemia, hypoglycemia, and no focal neurological deficits. What is the probable diagnosis?

A. Tubercular meningitis
B. Viral meningitis
C. Cerebral malaria (Correct Answer)
D. Fungal meningitis

Explanation: ***Cerebral malaria***- This diagnosis is strongly suggested by the sudden onset of high-grade fever, seizures, and loss of consciousness in a child, coupled with systemic complications like **anemia** and significant **hypoglycemia**.- Cerebral malaria, caused by *Plasmodium falciparum*, is a medical emergency where **hypoglycemia** results from high glucose consumption by parasites and impaired hepatic gluconeogenesis; **anemia** is also a key feature. *Tubercular meningitis*- Tuberculous meningitis typically presents with an **insidious, subacute onset** (over weeks) of fever, headache, and altered sensorium, not the sudden, explosive presentation described.- While it can cause neurological deficits, it is less commonly associated with the acute, severe systemic triad of high fever, profound **hypoglycemia**, and **anemia** seen here.*Viral meningitis*- Viral meningitis is usually associated with a milder clinical course and typically lacks the profound systemic complications like severe **anemia** and significant **hypoglycemia** that often precipitate seizures and coma in this age group.- Though high fever and seizures can occur, the presence of severe systemic features points away from typical viral etiologies and towards a systemic parasitic infection.*Fungal meningitis*- Fungal meningitis (e.g., *Cryptococcus*) is typically an **indolent or chronic infection** developing over weeks to months, primarily affecting **immunocompromised patients** (e.g., HIV/AIDS), which is unlikely in an otherwise healthy 8-year-old.- It rarely presents as an acute febrile illness with subsequent rapid onset of **anemia** and severe **hypoglycemia** leading to loss of consciousness.

Question 349: A 7-year-old child with a history of ear infection is complaining of lockjaw and limb spasm/fever/neck rigidity. Choose the most appropriate diagnosis:

A. Meningitis
B. Tetanus (Correct Answer)
C. Bezold abscess
D. Sinus thrombosis

Explanation: ***Tetanus*** - The striking combination of **lockjaw (trismus)** and generalized **limb spasms** is the hallmark clinical presentation of **Tetanus**, caused by the neurotoxin from *Clostridium tetani*. - The presence of **fever** and **neck rigidity** alongside an antecedent **ear infection** (potential portal of entry) strongly supports this diagnosis. - Tetanus causes sustained muscle contractions due to the inhibition of inhibitory neurons, leading to characteristic trismus, risus sardonicus, and opisthotonus. - Note: This is distinct from metabolic **tetany** (hypocalcemia), which causes carpopedal spasm without fever or lockjaw. *Incorrect: Meningitis* - While meningitis causes **fever** and **neck rigidity** (nuchal rigidity), it does not typically present with severe **lockjaw (trismus)** or sustained generalized **muscle spasms**. - Meningitis usually presents with headache, photophobia, altered consciousness, and positive Kernig's/Brudzinski's signs. *Incorrect: Bezold abscess* - A Bezold abscess is a deep neck abscess complicating mastoiditis, causing localized symptoms like neck pain, swelling, and **torticollis** (fixed head tilt). - It does not cause neuromuscular hyperexcitability resulting in **lockjaw** and widespread **limb spasms**. *Incorrect: Sinus thrombosis* - Lateral sinus thrombosis is a complication of otitis media presenting with **picket-fence fever**, headache, and signs of raised intracranial pressure. - It does not cause the characteristic muscle spasms and lockjaw seen in this presentation.

Question 350: An HIV-positive mother with a viral load of 1200 copies/mL delivers a baby. What is the most appropriate antiretroviral prophylaxis for the newborn?

A. Nevirapine + Zidovudine for 6 weeks (Correct Answer)
B. Zidovudine for 4 weeks
C. Nevirapine for 6 weeks
D. Nevirapine for 12 weeks

Explanation: ***Nevirapine + Zidovudine for 6 weeks*** - This combination is the recommended regimen for **high-risk newborns** in resource-limited settings, defined by a maternal viral load (MVL) greater than 1000 copies/mL or if maternal treatment was **suboptimal/absent**. - The dual prophylaxis provides comprehensive coverage to minimize the risk of **mother-to-child transmission (MTCT)**, which is elevated due to the high viral load (1200 copies/mL). *Nevirapine for 6 weeks* - **Nevirapine monotherapy** is reserved for **low-risk newborns** (MVL < 1000 copies/mL) or when the mother received adequate **antiretroviral therapy (ART)**. - Given the MVL of 1200 copies/mL, the risk is high, making dual therapy necessary. *Nevirapine for 12 weeks* - Extended NVP prophylaxis (12 weeks) is sometimes used if the infant is **breastfed and at high risk**, but current standard guidelines for non-breastfed infants with this MVL recommend 6 weeks of dual therapy. - **Duration of 12 weeks** is typically not the initial prophylaxis choice for a non-breastfed infant born to a mother with a high viral load. *Zidovudine for 4 weeks* - **Zidovudine monotherapy** for 4 weeks is considered inadequate given the mother's high viral load of **1200 copies/mL**. - This regimen (4 weeks of ZDV) is primarily reserved for **low-risk newborns** in settings where dual therapy is not feasible, or for term infants born to mothers with **fully suppressed viral loads** who received continuous ART.

Practice by Chapter

Vaccine-Preventable Diseases

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Immunization Schedule

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Common Childhood Infections

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Pediatric HIV

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Congenital Infections

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Fever in Infants and Children

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Meningitis and Encephalitis

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Respiratory Tract Infections

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Gastrointestinal Infections

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Parasitic Infections

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Tuberculosis in Children

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Opportunistic Infections

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