Infectious Diseases Practice Questions

Q: What is the most common cause of death in measles patients?

Pneumonia. **Explanation:** **Pneumonia** is the most common cause of death associated with measles in children, accounting for approximately 60% of measles-related fatalities. Measles virus causes profound immunosuppression by depleting T-lymphocytes and suppressing the immune response for weeks to months. This predisposes patients to secondary bacterial infections (most commonly *S. pneumoniae*, *H. influenzae*, and *S. aureus*) or primary giant cell pneumonia (Hecht’s pneumonia) caused by the virus itself. **Analysis of Incorrect Options:** * **Encephalitis:** While Acute Disseminated Encephalomyelitis (ADEM) and Subacute Sclerosing Panencephalitis (SSPE) are severe neurological complications, they occur much less frequently than respiratory complications. * **Meningitis:** This is not a classic or common complication of measles. Neurological involvement typically presents as encephalitis rather than isolated meningitis. * **Dehydration:** While diarrhea is the most common *complication* of measles overall (especially in developing countries), it is secondary to pneumonia as a cause of mortality. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication:** Diarrhea. * **Most common cause of death:** Pneumonia. * **Most common CNS complication:** Febrile seizures. * **Most common cause of long-term neurological mortality:** SSPE (occurs 7–10 years after infection; characterized by high titers of measles antibody in CSF). * **Vitamin A supplementation:** Essential in all children with measles to reduce the severity of complications and mortality. * **Koplik spots:** Pathognomonic sign found on the buccal mucosa opposite the lower second molars during the pre-eruptive stage.

Q: All are features of Pertussis except –

Cerebellar Ataxia. **Explanation:** Pertussis (Whooping Cough), caused by *Bordetella pertussis*, is characterized by severe paroxysms of coughing. The complications of Pertussis are primarily divided into those caused by **increased intrathoracic/intra-abdominal pressure** and those caused by **toxin-mediated effects**. **Why Cerebellar Ataxia is the Correct Answer:** Cerebellar ataxia is **not** a recognized feature of Pertussis. While Pertussis can involve the central nervous system (CNS), it typically manifests as encephalopathy. Ataxia is more commonly associated with viral infections like Varicella (post-infectious cerebellitis). **Analysis of Other Options:** * **Encephalopathy (Option A):** This is a known severe neurologic complication. It is thought to be caused by hypoxia during coughing fits, cerebral edema, or toxin-mediated effects. It presents as seizures or altered consciousness. * **Subconjunctival Hemorrhage (Option B):** During the paroxysmal stage, the intense pressure generated by forceful coughing causes the rupture of small capillaries. This leads to subconjunctival hemorrhages, epistaxis, and petechiae on the face/neck. * **Bronchiectasis (Option D):** Chronic or severe Pertussis can lead to secondary bacterial pneumonia and localized airway destruction, eventually resulting in bronchiectasis as a long-term pulmonary complication. **High-Yield Clinical Pearls for NEET-PG:** * **Stages:** Catarrhal (most infectious), Paroxysmal (whooping cough), and Convalescent. * **Hematology:** Characterized by **absolute lymphocytosis** (due to Lymphocytosis Promoting Factor), which is a rare finding in bacterial infections. * **Drug of Choice:** Macrolides (Azithromycin is preferred in infants). * **Gold Standard Diagnosis:** Culture on **Regan-Lowe** or **Bordet-Gengou** medium. * **Post-exposure Prophylaxis:** Recommended for all household contacts regardless of vaccination status.

Q: What is the most important element in the treatment of diphtheria?

Antitoxin. **Explanation:** The primary pathology in diphtheria is caused by the potent **exotoxin** produced by *Corynebacterium diphtheriae*. This toxin inhibits protein synthesis, leading to local tissue necrosis (pseudomembrane formation) and systemic complications like myocarditis and neuritis. Once the toxin binds to host cell receptors, it becomes irreversible. Therefore, the **most important** and life-saving element of treatment is the **Diphtheria Antitoxin (DAT)**. DAT works by neutralizing the circulating (unbound) toxin in the bloodstream before it can enter the cells. **Why the other options are incorrect:** * **Antibiotics (Erythromycin and Penicillin):** While essential, they are **secondary** to antitoxin. Antibiotics serve to stop further toxin production by killing the bacteria, prevent the spread of the organism to others, and treat the carrier state. They do not neutralize the toxin already present in the system. **Erythromycin** is generally considered the drug of choice for eradication. * **Tetracycline:** This is not a first-line agent for diphtheria and is less effective than macrolides or penicillins. **High-Yield Clinical Pearls for NEET-PG:** * **Schick Test:** Used to determine the immune status of an individual toward diphtheria. * **Loffler’s Serum Slope/Tellurite Medium:** Specific culture media used for growth (colonies appear grey-black on Tellurite). * **Albert’s Stain:** Used to demonstrate metachromatic (volutin) granules. * **Treatment Priority:** In clinical practice, DAT should be administered as soon as a clinical diagnosis is made, without waiting for laboratory confirmation, as delay increases the risk of mortality.

Q: Hecht's pneumonia is a complication of which condition?

Measles. **Explanation:** **Hecht’s Pneumonia**, also known as **Giant Cell Interstitial Pneumonia**, is a severe and often fatal complication of **Measles (Rubeola)**. It typically occurs in immunocompromised children (e.g., those with leukemia or HIV) who fail to develop the characteristic measles rash due to impaired T-cell immunity. 1. **Why Measles is Correct:** The measles virus causes the fusion of infected cells, leading to the formation of **Warthin-Finkeldey giant cells** (multinucleated giant cells with eosinophilic intranuclear and intracytoplasmic inclusion bodies) in the lymphoid and pulmonary tissues. In Hecht’s pneumonia, these giant cells infiltrate the alveolar walls, leading to progressive respiratory failure. 2. **Why Other Options are Incorrect:** * **Mumps:** Primarily involves the parotid glands and testes; respiratory complications are rare and do not manifest as Hecht’s pneumonia. * **AIDS:** While patients with AIDS are at high risk for Hecht’s pneumonia if they contract measles, the pneumonia itself is specifically etiologically linked to the measles virus, not HIV. * **Mycoplasma:** Causes "Walking Pneumonia" characterized by interstitial infiltrates and cold agglutinins, but does not produce multinucleated giant cells. **High-Yield Clinical Pearls for NEET-PG:** * **Warthin-Finkeldey Cells:** Pathognomonic for Measles; found in nasal secretions, tonsils, and lung tissue. * **Koplik Spots:** The hallmark prodromal sign of measles (found opposite the lower second molars). * **Vitamin A:** Supplementation is recommended for all children with acute measles to reduce morbidity and mortality. * **SSPE (Subacute Sclerosing Panencephalitis):** A late neurological complication occurring years after a primary measles infection.

Q: At what age is the MMR vaccination typically given?

18 months. **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.

Q: What is the most common cause of neonatal meningitis?

E. coli. **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).

Q: 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?

Reassure the mother. ***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.

Q: 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)

Measles. ***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.

Q: 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?

Cerebral malaria. ***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 1

What is the most common cause of death in measles patients?

Accepted Answer

Pneumonia

Answer

Encephalitis

Answer

Meningitis

Answer

Dehydration

Question 2

All are features of Pertussis except –

Accepted Answer

Cerebellar Ataxia

Answer

Encephalopathy

Answer

Subconjunctival hemorrhage

Answer

Bronchiectasis

Question 3

What is the most important element in the treatment of diphtheria?

Accepted Answer

Antitoxin

Answer

Tetracycline

Answer

Erythromycin

Answer

Penicillin

Question 4

Hecht's pneumonia is a complication of which condition?

Accepted Answer

Measles

Answer

Mumps

Answer

AIDS

Answer

Mycoplasma

Question 5

At what age is the MMR vaccination typically given?

Accepted Answer

18 months

Answer

Birth

Answer

6 months

Answer

1 year

Question 6

What is the most common cause of neonatal meningitis?

Accepted Answer

E. coli

Answer

Staphylococcus

Answer

H. influenzae

Answer

Pneumococcus

Question 7

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?

Accepted Answer

Reassure the mother

Answer

Do the Mantoux test & wait for the result

Answer

Refer the baby for a chest X-ray & further evaluation

Answer

Give the BCG vaccine immediately

Question 8

An unvaccinated 5-year-old child of a migrant worker family was brought to the casualty with fever and a characteristic skin rash. Upon eye examination, Bitot's spot was seen. What is the appropriate management?

Accepted Answer

Isolate and give nutritional supply with vitamin A supplement

Answer

Only measles vaccine

Answer

Institutional Isolation, nutritional management with vitamin A supplement

Answer

Give measles vaccine and vitamin A supplement

Question 9

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)

Accepted Answer

Measles

Answer

Chickenpox

Answer

Mumps

Answer

Erythema infectiosum

Question 10

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?

Accepted Answer

Cerebral malaria

Answer

Tubercular meningitis

Answer

Viral meningitis

Answer

Fungal meningitis

Infectious Diseases — MCQs

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