Infectious Diseases Practice Questions

Q: A 8-year-old boy presented with swelling on both sides of the face, below the ears, of 4 days duration. The swelling first started on the left side and then, 3 days later, appeared on the right side. Immunization to this disease can be achieved by which of the following vaccinations?

MMR. **Explanation:** The clinical presentation of bilateral facial swelling below the ears, starting on one side and progressing to the other, is a classic description of **Parotitis**, the hallmark of **Mumps**. Mumps is an acute viral infection caused by the *Rubulavirus* (Paramyxoviridae family). **Why MMR is correct:** The **MMR (Measles, Mumps, and Rubella)** vaccine is a live-attenuated vaccine that provides effective immunity against the Mumps virus. In the National Immunization Schedule (India) and IAP guidelines, it is typically administered in two doses (at 9 months as MR/MMR and 15 months as MMR). **Why other options are incorrect:** * **BCG (Bacillus Calmette-Guérin):** A live bacterial vaccine used to prevent severe forms of Tuberculosis (miliary and meningeal TB). * **Hepatitis B:** A subunit vaccine (HBsAg) used to prevent viral hepatitis caused by the Hepatitis B virus. * **Polio:** Administered as OPV (Sabin - live) or IPV (Salk - inactivated) to prevent poliomyelitis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication in children:** Aseptic meningitis. * **Most common complication in post-pubertal males:** Epididymo-orchitis (usually unilateral; rarely leads to sterility). * **Other complications:** Pancreatitis (look for elevated serum amylase), Oophoritis, and Sensorineural hearing loss (usually unilateral). * **Infectivity:** Patients are most infectious from 2 days before to 5 days after the onset of parotid swelling. * **Diagnosis:** Primarily clinical; however, IgM antibodies or PCR can confirm the diagnosis.

Q: What is the approximate percentage of HIV transmission from an infected mother to her child?

20% – 30%. **Explanation:** The transmission of HIV from an infected mother to her child is known as **Vertical Transmission** or Mother-to-Child Transmission (MTCT). In the absence of any medical intervention (antiretroviral therapy, elective cesarean section, or avoidance of breastfeeding), the risk of transmission is approximately **20% to 30%**. **Breakdown of Transmission Timing:** * **In-utero (Transplacental):** ~5%–10% * **Intrapartum (During delivery):** ~10%–15% (Most common route) * **Postpartum (Breastfeeding):** ~5%–20% (Cumulative risk) **Analysis of Options:** * **Option A (20% – 30%):** Correct. This represents the standard global average for vertical transmission in non-interventional settings. * **Option B (10% – 20%):** Incorrect. This range is too low for a mother who is breastfeeding without treatment, though it may approximate the risk if breastfeeding is strictly avoided. * **Option C (70% – 80%):** Incorrect. HIV is not transmitted to every fetus; the placental barrier and maternal immune factors provide significant protection. * **Option D (100%):** Incorrect. Transmission is never guaranteed; even without treatment, the majority of infants born to HIV-positive mothers are born HIV-negative. **High-Yield Clinical Pearls for NEET-PG:** 1. **Prevention of Parent-to-Child Transmission (PPTCT):** With effective HAART (Highly Active Antiretroviral Therapy) and a suppressed maternal viral load, the risk can be reduced to **<1%–2%**. 2. **Most Common Route:** The **intrapartum period** (exposure to maternal blood and vaginal secretions) carries the highest risk. 3. **Diagnosis in Infants:** HIV DNA PCR (Nucleic Acid Test) is the gold standard for infants <18 months. Antibody tests (ELISA) are unreliable due to the persistence of maternal IgG antibodies. 4. **Prophylaxis:** In India, the NACP guidelines recommend **Nevirapine** syrup for the infant for at least 6 weeks.

Q: Raspberry tongue is seen in which of the following conditions?

Scarlet fever. **Explanation:** **Scarlet Fever (Correct Answer):** Scarlet fever is caused by **Group A Streptococcus (Streptococcus pyogenes)** producing **Erythrogenic (Pyrogenic) toxins**. The "Raspberry tongue" is a classic clinical sign that evolves in stages. Initially, the tongue has a white coating with red, hypertrophied papillae projecting through it (**White Strawberry Tongue**). By day 4 or 5, the white coat desquamates, leaving a bright red, denuded surface with prominent papillae, known as the **Red Strawberry or Raspberry Tongue**. **Analysis of Incorrect Options:** * **Vitiligo:** This is an autoimmune skin disorder characterized by the loss of melanocytes, leading to depigmented white patches. It does not affect the tongue in this inflammatory manner. * **Vitamin B12 deficiency:** This typically causes a **"Beefy red tongue"** or Hunter’s glossitis, where the tongue appears smooth and shiny due to the atrophy of lingual papillae (atrophic glossitis), rather than the prominent papillae seen in Scarlet fever. * **Impetigo:** Also caused by *S. pyogenes* or *S. aureus*, this is a superficial skin infection characterized by "honey-colored crusts." It does not typically involve the tongue. **NEET-PG High-Yield Pearls:** * **Dick Test:** Historically used to determine susceptibility to Scarlet fever. * **Schultz-Charlton Reaction:** A diagnostic test where antitoxin injected into the skin causes blanching of the Scarlet fever rash. * **Pastia’s Lines:** Pink or red lines in skin creases (axilla/groin) seen in Scarlet fever. * **Differential Diagnosis:** Strawberry tongue is also a major diagnostic criterion for **Kawasaki Disease**.

Q: Congenital rubella causes all EXCEPT:

Hydrocephalus. **Explanation:** Congenital Rubella Syndrome (CRS) is caused by the transplacental transmission of the Rubella virus, typically during the first trimester. The classic clinical presentation is defined by **Gregg’s Triad**, which includes sensorineural deafness, eye anomalies, and congenital heart disease. **Why Hydrocephalus is the correct answer:** Hydrocephalus is **not** a feature of Congenital Rubella. Instead, the hallmark neurological finding in CRS is **Microcephaly** (small head size due to impaired brain growth). Hydrocephalus is more characteristically associated with **Congenital Toxoplasmosis** (part of the classic triad: hydrocephalus, chorioretinitis, and intracranial calcifications). **Analysis of Incorrect Options:** * **A. Deafness:** Sensorineural hearing loss is the **most common** manifestation of CRS, occurring in about 80% of affected infants. * **B. Cataract:** Ocular defects are common, with "pearlescent" nuclear cataracts and "salt-and-pepper" retinopathy being high-yield findings. * **C. Cardiac defects:** The most characteristic lesion is **Patent Ductus Arteriosus (PDA)**, followed by peripheral pulmonary artery stenosis. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad:** Cataract, Deafness, and PDA. * **Skin manifestation:** "Blueberry muffin" rash (due to extramedullary hematopoiesis). * **Radiology:** "Celery stalking" appearance (longitudinal radiolucent striations in the metaphysis of long bones). * **Timing:** Risk is highest (up to 90%) if maternal infection occurs before 11 weeks of gestation. * **Diagnosis:** Detection of Rubella-specific IgM in the newborn or persistence of IgG titers beyond 6–12 months.

Q: Which of the following is NOT a complication of mumps?

Hepatitis. **Explanation:** Mumps is an acute viral illness caused by the **Rubulavirus** (Paramyxoviridae family), primarily characterized by painful swelling of the parotid glands. While the virus is systemic and can affect various glandular and neurological tissues, **Hepatitis (Option D)** is not a recognized or typical complication of mumps. Liver involvement is extremely rare, making it the correct answer for this "except" type question. **Analysis of Complications:** * **Orchitis (Option A):** This is the most common complication in post-pubertal males (occurring in up to 30-40% of cases). It is usually unilateral and can lead to testicular atrophy, though permanent infertility is rare. * **Oophoritis (Option B):** Occurring in about 5-7% of post-pubertal females, it presents with pelvic pain and tenderness but rarely affects fertility. * **Encephalitis (Option C):** Neurological involvement is common. While **aseptic meningitis** is the most frequent neurological complication, true encephalitis (direct brain parenchyma involvement) occurs in about 1 in 1,000 cases and is a significant cause of mumps-related morbidity. **High-Yield Clinical Pearls for NEET-PG:** * **Pancreatitis:** Mumps is a classic viral cause of acute pancreatitis. * **Deafness:** Mumps is a leading cause of **sudden onset sensorineural hearing loss** (usually unilateral) in children. * **Most common complication in children:** Aseptic meningitis. * **Most common complication in post-pubertal males:** Orchitis. * **Incubation Period:** 14–21 days. * **Infectivity:** Patients are most infectious from 2 days before to 5 days after the onset of parotitis.

Q: A 10-year-old child presents with a 10-day history of continuous fever, accompanied by a soft, enlarged spleen. What is the most likely diagnosis?

Enteric fever. **Explanation:** The clinical presentation of **continuous fever** lasting for more than a week, associated with a **soft, enlarged spleen**, is a classic hallmark of **Enteric Fever** (Typhoid/Paratyphoid). 1. **Why Enteric Fever is correct:** In the first week of Enteric fever, the temperature rises in a "step-ladder" fashion, becoming continuous by the second week. Splenomegaly typically appears at the end of the first week or during the second week. Crucially, the spleen in Enteric fever is **soft and mildly tender**, unlike the firm/hard spleen seen in chronic infections or malignancies. 2. **Why other options are incorrect:** * **Malaria:** Characterized by intermittent fever with chills and rigors (paroxysms), rather than a continuous fever pattern. The spleen in malaria becomes firm over time. * **Hodgkin’s Disease:** Usually presents with painless, rubbery lymphadenopathy. While it can cause fever (Pel-Ebstein type) and splenomegaly, the spleen is typically firm, and the fever is rarely the sole presenting symptom for only 10 days. * **Meningitis:** Presents with acute onset high-grade fever, headache, vomiting, and signs of meningeal irritation (neck stiffness). Splenomegaly is not a standard feature. **NEET-PG High-Yield Pearls:** * **Gold Standard Diagnosis:** Bone marrow culture (most sensitive); Blood culture (positive in 1st week). * **Widal Test:** Significant only after the 2nd week (look for a four-fold rise in titers). * **Relative Bradycardia (Faget’s sign):** Pulse rate is slower than expected for the degree of fever; a key diagnostic clue. * **Rose Spots:** Faint, salmon-colored macules on the trunk (seen in the 2nd week).

Q: What is helpful in a child with severe falciparum malaria with high parasitemia?

Exchange transfusion. **Explanation:** Severe falciparum malaria is a medical emergency characterized by high parasite density (hyperparasitemia) and multi-organ dysfunction. **Why Exchange Transfusion is correct:** Exchange transfusion is considered an adjunctive therapy in severe malaria, particularly when parasitemia exceeds **10-15%** or if there are signs of organ failure (e.g., cerebral malaria, ARDS, or renal failure). The procedure works by: 1. **Rapidly reducing parasite load:** Physically removing infected red blood cells (RBCs). 2. **Improving Rheology:** Removing rigid, parasitized RBCs that cause microvascular sequestration and replacing them with flexible donor cells, thereby improving tissue perfusion. 3. **Reducing Toxicity:** Clearing parasite-derived toxins, cytokines, and free hemoglobin. **Why other options are incorrect:** * **IV Corticosteroids:** Previously used for cerebral malaria to reduce brain edema, clinical trials (like those by Warrell et al.) proved they are **contraindicated**. They increase the risk of secondary infections and gastrointestinal bleeding without improving survival. * **Hyperbaric Oxygen:** There is no established clinical evidence or physiological basis for its use in treating the pathophysiology of malaria. **NEET-PG High-Yield Pearls:** * **WHO Criteria for Hyperparasitemia:** >10% in low-transmission areas or >20% in high-transmission areas. * **Drug of Choice:** IV **Artesunate** is the gold standard for severe malaria (superior to Quinine). * **Common Complication in Children:** Hypoglycemia and severe anemia are more frequent in pediatric severe malaria compared to adults. * **Blackwater Fever:** Characterized by massive intravascular hemolysis and hemoglobinuria, often associated with Quinine use.

Q: Excessive crying is a known side effect following which vaccination?

DPT. **Explanation:** The correct answer is **DPT (Diphtheria, Pertussis, and Tetanus)**. **Why DPT is the correct answer:** Excessive crying (defined as persistent, inconsolable crying lasting for 3 hours or more) is a well-documented systemic adverse event following immunization (AEFI) specifically associated with the **whole-cell Pertussis (wP)** component of the DPT vaccine. This reaction typically occurs within 2–24 hours of administration. It is thought to be caused by the local inflammatory response and systemic effects of the endotoxins present in the *Bordetella pertussis* bacteria. While distressing to parents, it is usually self-limiting and not a contraindication to future doses, though acellular pertussis (aP) vaccines are associated with a significantly lower incidence of this side effect. **Why other options are incorrect:** * **Polio (OPV/IPV):** Generally very well tolerated. The most serious (though rare) side effect of OPV is Vaccine-Associated Paralytic Poliomyelitis (VAPP), not excessive crying. * **BCG:** Typically causes local reactions such as a papule, ulcer, and eventual scarring at the injection site. Systemic reactions like persistent crying are rare. * **Measles:** Common side effects include fever and a transient rash occurring 5–12 days after vaccination, rather than immediate excessive crying. **High-Yield Clinical Pearls for NEET-PG:** * **Persistent Inconsolable Crying:** Occurs in approximately 1% of children receiving the wP vaccine. * **Absolute Contraindications to Pertussis vaccine:** Encephalopathy (e.g., coma, seizures) within 7 days of a previous dose. * **Triple Response:** DPT is also associated with local pain, swelling, and redness at the injection site. * **Switching to DTaP:** If a child experiences severe reactions to DTwP, the acellular version (DTaP) is preferred for subsequent doses.

Q: A 9-year-old girl presents with a 2-day history of sore throat. Physical examination reveals pharyngeal erythema with yellowish exudates over swollen palatine tonsils. A Gram stain of the exudate shows gram-positive cocci in chains. She is treated with penicillin. What is the most likely complication prevented by prompt treatment?

Carditis. **Explanation:** The clinical presentation of sore throat, pharyngeal exudates, and Gram-positive cocci in chains is diagnostic of **Acute Pharyngitis** caused by **Group A Streptococcus (GAS)**, specifically *Streptococcus pyogenes*. **Why Carditis is correct:** Prompt antibiotic treatment (within 9 days of symptom onset) is primarily aimed at preventing **Acute Rheumatic Fever (ARF)**. ARF is a nonsuppurative, immune-mediated complication caused by molecular mimicry between streptococcal M-proteins and human cardiac tissue. **Carditis** is the most serious manifestation of ARF and can lead to permanent valvular damage. Notably, while antibiotics prevent ARF, they do **not** prevent Post-Streptococcal Glomerulonephritis (PSGN). **Why other options are incorrect:** * **Hepatitis:** This is not a recognized complication of *S. pyogenes* infection. * **Meningitis:** While GAS can rarely cause meningitis via hematogenous spread or local extension, it is not the primary complication targeted by routine penicillin therapy for pharyngitis. * **Otitis:** Otitis media is a common *suppurative* complication of streptococcal pharyngitis. While penicillin reduces its incidence, the most critical "preventable" systemic sequela emphasized in medical exams is the life-altering carditis associated with ARF. **High-Yield NEET-PG Pearls:** * **Jones Criteria:** Used for diagnosing ARF (Major: Carditis, Polyarthritis, Chorea, Erythema marginatum, Subcutaneous nodules). * **ASO Titre:** Elevated Anti-Streptolysin O (ASO) titers indicate recent streptococcal infection. * **Drug of Choice:** Penicillin remains the gold standard for GAS pharyngitis due to 100% sensitivity. * **PSGN vs. ARF:** Antibiotics prevent ARF but **not** PSGN. PSGN can follow both skin (impetigo) and throat infections, whereas ARF follows **only** pharyngeal infections.

Question 1

A 8-year-old boy presented with swelling on both sides of the face, below the ears, of 4 days duration. The swelling first started on the left side and then, 3 days later, appeared on the right side. Immunization to this disease can be achieved by which of the following vaccinations?

Accepted Answer

MMR

Answer

BCG

Answer

Hepatitis B

Answer

Polio

Question 2

A lactating woman has sputum positive TB. The neonate is 3 months old. What is the recommended chemoprophylaxis?

Accepted Answer

INH 5mg/kg for 6 months

Answer

INH 3mg/kg for 3 months

Answer

INH 5mg/kg for 3 months

Answer

INH 3mg/kg for 6 months

Question 3

What is the approximate percentage of HIV transmission from an infected mother to her child?

Accepted Answer

20% – 30%

Answer

10% – 20%

Answer

70% – 80%

Answer

100%

Question 4

Raspberry tongue is seen in which of the following conditions?

Accepted Answer

Scarlet fever

Answer

Vitiligo

Answer

Vitamin B12 deficiency

Answer

Impetigo

Question 5

Congenital rubella causes all EXCEPT:

Accepted Answer

Hydrocephalus

Answer

Deafness

Answer

Cataract

Answer

Cardiac defects

Question 6

Which of the following is NOT a complication of mumps?

Accepted Answer

Hepatitis

Answer

Orchitis

Answer

Oophoritis

Answer

Encephalitis

Question 7

A 10-year-old child presents with a 10-day history of continuous fever, accompanied by a soft, enlarged spleen. What is the most likely diagnosis?

Accepted Answer

Enteric fever

Answer

Malaria

Answer

Hodgkin's disease

Answer

Meningitis

Question 8

What is helpful in a child with severe falciparum malaria with high parasitemia?

Accepted Answer

Exchange transfusion

Answer

IV corticosteroids

Answer

Hyperbaric oxygen

Answer

All the above

Question 9

Excessive crying is a known side effect following which vaccination?

Accepted Answer

DPT

Answer

Polio

Answer

BCG

Answer

Measles

Question 10

A 9-year-old girl presents with a 2-day history of sore throat. Physical examination reveals pharyngeal erythema with yellowish exudates over swollen palatine tonsils. A Gram stain of the exudate shows gram-positive cocci in chains. She is treated with penicillin. What is the most likely complication prevented by prompt treatment?

Accepted Answer

Carditis

Answer

Hepatitis

Answer

Meningitis

Answer

Otitis

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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