Infectious Diseases Practice Questions

Q: A two-year-old unimmunized child presents with fever for 5 days and a rash behind the ear that appeared the day before presentation. The child also has a running nose and congested eyes. What is the most probable diagnosis?

Measles. **Explanation:** The clinical presentation is classic for **Measles (Rubeola)**. The diagnosis is based on the following high-yield features: 1. **Prodromal Phase:** Fever, rhinorrhea (running nose), and conjunctivitis (congested eyes) are the hallmark "3 Cs" (Cough, Coryza, Conjunctivitis). 2. **Rash Progression:** The rash in measles typically appears on the 4th or 5th day of fever. It is a maculopapular rash that characteristically starts **behind the ears** (at the hairline) and spreads cephalocaudally (downward) to the face, trunk, and extremities. 3. **Immunization Status:** Being "unimmunized" is a significant risk factor, as the first dose of the MR/MMR vaccine is typically given at 9 months. **Why other options are incorrect:** * **Rubella (German Measles):** While the rash also spreads downward, the prodrome is much milder (low-grade fever), and the most characteristic finding is **post-auricular/suboccipital lymphadenopathy**, not severe coryza. * **Mumps:** This primarily presents with painful swelling of the **parotid glands**, not a maculopapular rash. * **Chickenpox (Varicella):** The rash is **pleomorphic** (vesicles, pustules, and scabs present simultaneously) and typically starts on the trunk ("centripetal" distribution), appearing in crops. **NEET-PG High-Yield Pearls:** * **Koplik Spots:** Pathognomonic for measles; seen on the buccal mucosa opposite the lower 2nd molar *before* the rash appears. * **Vitamin A:** Supplementation is mandatory in all children with measles to prevent complications like blindness and pneumonia. * **Infectivity:** Most infectious during the prodromal stage (4 days before to 4 days after the appearance of the rash). * **Subacute Sclerosing Panencephalitis (SSPE):** A rare, delayed neurological complication occurring years after the initial infection.

Q: Massive myoclonus is a hallmark of which stage of Subacute Sclerosing Panencephalitis (SSPE)?

Stage 2. Subacute Sclerosing Panencephalitis (SSPE) is a progressive, fatal neurodegenerative disease caused by a persistent infection with a mutant Measles virus. The clinical progression is classically divided into four stages [1]: * **Stage 1 (Behavioral):** Characterized by subtle changes including irritability, social withdrawal, and declining school performance. * **Stage 2 (Motor Regression):** This is the stage where **massive myoclonus** (periodic, synchronous muscle jerks) occurs. It is the hallmark of this stage, often accompanied by worsening motor coordination and seizures. * **Stage 3 (Extrapyramidal):** Myoclonus disappears and is replaced by severe extrapyramidal symptoms, including choreoathetosis, dystonia, and spasticity. * **Stage 4 (Terminal):** The patient enters a vegetative state, characterized by akinetic mutism, decorticate/decerebrate rigidity, and eventually death. **Why Stage 2 is correct:** Massive myoclonus is the defining clinical feature of Stage 2. These jerks are typically "slow," lasting 1–3 seconds, and involve the head, trunk, and limbs. **High-Yield Clinical Pearls for NEET-PG:** * **EEG Finding:** Characterized by **Radermecker complexes** (periodic, high-voltage, generalized slow-wave complexes). * **Diagnosis:** Elevated titers of **anti-measles antibodies** in both serum and CSF (intrathecal synthesis) [1]. * **CSF Analysis:** Shows a normal cell count but significantly elevated **gamma globulin** levels (oligoclonal bands). * **Risk Factor:** Early-age measles infection (usually <2 years old) with a latency period of 5–10 years.

Q: Which of the following signs and symptoms should arouse suspicion of streptococcal sore throat?

All of the above. ### Explanation The diagnosis of **Group A Beta-Hemolytic Streptococcus (GABHS)** pharyngitis is primarily clinical, often guided by the **Centor Criteria** or the **McIsaac Score**. The goal is to differentiate bacterial infection from viral pharyngitis to ensure appropriate antibiotic stewardship. **Why "All of the above" is correct:** Streptococcal sore throat typically presents with an acute onset of symptoms that are localized to the oropharynx and lack the systemic "catarrhal" features of a viral upper respiratory infection. * **Exudates in the throat (Option A):** Patchy grayish-white tonsillar exudates are a classic sign of GABHS, though they can also be seen in Infectious Mononucleosis. * **Tender enlarged cervical lymph nodes (Option B):** Anterior cervical lymphadenopathy (specifically tender nodes) is a hallmark of bacterial pharyngitis. * **Absence of nasal and conjunctival injection (Option C):** This is a **crucial negative predictor**. The presence of cough, coryza (nasal congestion), conjunctivitis, or hoarseness strongly suggests a **viral etiology** (like Adenovirus or Rhinovirus) rather than Streptococcus. **High-Yield Clinical Pearls for NEET-PG:** 1. **Centor Criteria:** Points are given for: (1) Fever, (2) Tonsillar exudates, (3) Tender anterior cervical lymphadenopathy, and (4) **Absence of cough**. 2. **Age Factor:** GABHS is most common in children aged **5–15 years**. It is rare in children under 3 years. 3. **Scarlet Fever:** If a "sandpaper" rash and strawberry tongue accompany the sore throat, suspect Scarlet Fever (caused by erythrogenic toxins). 4. **Gold Standard Diagnosis:** Throat culture remains the gold standard, though Rapid Antigen Detection Tests (RADT) are used for immediate bedside screening. 5. **Treatment:** Penicillin V or Amoxicillin is the drug of choice to prevent **Acute Rheumatic Fever**.

Q: Which of the following is NOT a contraindication to DPT vaccination?

Fever. In pediatric immunization, distinguishing between **true contraindications** and **false contraindications** is a high-yield topic for NEET-PG. ### **Why Fever is the Correct Answer** **Fever** (mild to moderate) or a minor acute illness (e.g., common cold, diarrhea) is a **false contraindication** for DPT vaccination. According to WHO and IAP guidelines, vaccines should not be delayed for minor illnesses, as this leads to missed opportunities for immunization. Only a severe, life-threatening acute illness would warrant deferral until the child recovers. ### **Analysis of Incorrect Options (True Contraindications)** The following are absolute contraindications to the Pertussis component of the DPT vaccine: * **History of Anaphylaxis (Option A):** Any immediate severe allergic reaction to a prior dose or vaccine component is an absolute contraindication to further doses. * **Progressive Neurologic Illness (Option B):** Conditions such as uncontrolled epilepsy, infantile spasms, or progressive encephalopathy require deferring the pertussis vaccine until the neurologic status is stabilized. * **Encephalopathy (Option D):** Any encephalopathy (e.g., coma, prolonged seizures) occurring within 7 days of a previous DPT dose, not attributable to another cause, is a contraindication. ### **High-Yield Clinical Pearls for NEET-PG** * **DT vs. DPT:** If a child has a contraindication to the Pertussis component, the immunization series should be completed using the **DT (Diphtheria and Tetanus)** vaccine. * **Precautions (Not Contraindications):** A history of febrile seizures, a family history of seizures, or stable neurologic conditions (like well-controlled cerebral palsy) are **not** contraindications. * **The "7-Day Rule":** Always remember the 7-day window for encephalopathy specifically linked to the Pertussis fraction.

Q: A 14-month-old child, unvaccinated against H. influenzae, presents to the OPD. How many doses, including the booster, should be administered?

2 doses. **Explanation:** The number of doses of the *Haemophilus influenzae* type b (Hib) vaccine required is determined by the **age at which the primary series is initiated**. This is due to the age-related development of natural immunity and the increased immunogenicity of the conjugate vaccine in older infants. **Why 2 doses is correct:** According to standard immunization guidelines (IAP and WHO), if a child starts the Hib vaccination late, between **12 to 15 months of age**, the recommended schedule is **2 doses**, administered at an interval of 8 weeks (2 months). Beyond 12 months, the child’s immune system responds more robustly to the polysaccharide-protein conjugate, requiring fewer doses to achieve protective antibody titers compared to an infant. **Analysis of Incorrect Options:** * **A & B (4 or 3 doses):** These schedules are for infants starting the series in early infancy (e.g., at 6, 10, and 14 weeks as part of the Pentavalent vaccine). A 4th dose (booster) is typically given at 15-18 months if the series started early. * **D (1 dose):** A single dose is only sufficient if the child is initiated between **15 months and 5 years** of age. After 5 years, the vaccine is generally not recommended for healthy children as the risk of invasive Hib disease significantly decreases. **NEET-PG High-Yield Pearls:** * **Catch-up Schedule for Hib:** * 7–11 months: 2 doses + 1 booster (Total 3). * 12–15 months: 2 doses (Total 2). * 15 months–5 years: 1 dose (Total 1). * **Type of Vaccine:** Hib is a **conjugate vaccine** (capsular polysaccharide PRP conjugated to a carrier protein like Tetanus Toxoid). * **National Immunization Schedule (NIS):** In India, Hib is administered as part of the **Pentavalent vaccine** (DPT + HepB + Hib) at 6, 10, and 14 weeks.

Q: A young child presents with a low-grade fever, coryza, sore throat, a bright red rash on his cheeks, and a less intense erythematous rash on his body. Elevated IgG and IgM antibody titers to parvovirus suggest a diagnosis of which of the following?

Fifth disease. **Explanation:** The clinical presentation described—low-grade fever followed by a characteristic **"slapped-cheek"** appearance and a reticular (lace-like) body rash—is the classic manifestation of **Erythema Infectiosum**, also known as **Fifth Disease**. This condition is caused by **Parvovirus B19**, a small, non-enveloped DNA virus. The presence of elevated IgM antibodies indicates an acute infection, while IgG signifies immune response/past exposure. **Why the other options are incorrect:** * **Acute Lyme Disease:** Caused by *Borrelia burgdorferi*, it typically presents with *Erythema migrans* (a "bull’s-eye" rash), not a slapped-cheek rash, and is associated with tick bites. * **Hepatitis B Infection:** While Parvovirus B19 can cause transient aplastic crisis, it is not a cause of Hepatitis B. HBV presents with jaundice, hepatomegaly, and specific serological markers (HBsAg, anti-HBc). * **Subacute Sclerosing Panencephalitis (SSPE):** This is a rare, fatal, progressive neurological complication occurring years after a **Measles** infection, characterized by cognitive decline and myoclonus, not an acute childhood rash. **High-Yield Clinical Pearls for NEET-PG:** * **Receptor:** Parvovirus B19 binds to the **P-antigen** (globoside) on erythroid progenitor cells. * **Complications:** 1. **Aplastic Crisis:** In patients with high RBC turnover (e.g., Sickle Cell Anemia, Hereditary Spherocytosis). 2. **Hydrops Fetalis:** If a pregnant woman is infected, the virus crosses the placenta, causing severe fetal anemia and high-output cardiac failure. 3. **Arthropathy:** More common in adults (symmetrical small joint involvement). * **Diagnosis:** PCR is the most sensitive test for immunocompromised patients; serology (IgM) is used for immunocompetent individuals.

Q: A child is suffering from varicella (fever rash). The child's aunt is pregnant. When is it earliest that the child can meet her aunt?

When the lesions have crusted. **Explanation:** The core medical concept here is the **period of communicability** of the Varicella-Zoster Virus (VZV). Varicella (Chickenpox) is highly contagious and is transmitted via respiratory droplets or direct contact with vesicle fluid. **1. Why Option A is correct:** A patient with chickenpox is infectious 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 shedding from the skin, and the child is no longer considered contagious. Meeting a pregnant woman before this stage poses a significant risk of **Congenital Varicella Syndrome** (if early in pregnancy) or neonatal varicella. **2. Why other options are incorrect:** * **Option B & C:** These are incorrect because the child is actively shedding the virus during the vesicular stage. Emotional bonds do not mitigate the risk of viral transmission. * **Option D:** This is unnecessarily restrictive. While caution is needed, the child is safe to be around others once the period of communicability has ended (crusting), which usually occurs within 5–7 days of rash onset. **High-Yield Clinical Pearls for NEET-PG:** * **Incubation Period:** 10–21 days (Average 14–16 days). * **Rash Characteristics:** "Pleomorphic" (all stages of rash—papules, vesicles, and crusts—seen simultaneously) and "Dewdrop on a rose petal" appearance. * **Congenital Varicella Syndrome:** Highest risk if maternal infection occurs between 8–20 weeks of gestation; characterized by limb hypoplasia, cicatricial skin scarring, and microcephaly. * **Post-Exposure Prophylaxis:** For susceptible pregnant women exposed to VZV, **Varicella-Zoster Immunoglobulin (VZIG)** should be administered within 10 days of exposure.

Question 1

What is true regarding Lymphocytic interstitial pneumonitis (LIP)?

Accepted Answer

May be associated with hepatosplenomegaly

Answer

Is common in vertically acquired HIV infection

Answer

Is due to a protozoal infection

Answer

Is seen on chest X-ray as a perihilar infiltration in a butterfly distribution

Question 2

A two-year-old unimmunized child presents with fever for 5 days and a rash behind the ear that appeared the day before presentation. The child also has a running nose and congested eyes. What is the most probable diagnosis?

Accepted Answer

Measles

Answer

Rubella

Answer

Mumps

Answer

Chickenpox

Question 3

Which of the following findings is LEAST suggestive of poliovirus infection?

Accepted Answer

Descending motor paralysis with preservation of tendon reflexes and sensation

Answer

Low grade fever and malaise with complete resolution in 2 to 3 days

Answer

Biphasic illness with several days of fever, then meningeal symptoms and asymmetric flaccid paralysis 5 to 10 days later

Answer

Failure to isolate a virus from the cerebrospinal fluid in the presence of marked meningismus

Question 4

Massive myoclonus is a hallmark of which stage of Subacute Sclerosing Panencephalitis (SSPE)?

Accepted Answer

Stage 2

Answer

Stage 1

Answer

Stage 3

Answer

Stage 4

Question 5

Which of the following statements is FALSE about diphtheria?

Accepted Answer

Antidiphtheria serum (20,000-100,000 units) is administered in cutaneous diphtheria.

Answer

The most common location for pseudomembrane formation is the fauces.

Answer

Diphtheria is primarily a toxaemia.

Answer

Myocarditis is a common complication of diphtheria.

Question 6

Which of the following signs and symptoms should arouse suspicion of streptococcal sore throat?

Accepted Answer

All of the above

Answer

Exudates in the throat

Answer

Tender enlarged cervical lymph nodes

Answer

Absence of nasal and conjunctival injection

Question 7

Which of the following is NOT a contraindication to DPT vaccination?

Accepted Answer

Fever

Answer

History of anaphylaxis to a previous dose

Answer

Progressive neurologic illness

Answer

Encephalopathy within 7 days of a previous dose

Question 8

A 14-month-old child, unvaccinated against H. influenzae, presents to the OPD. How many doses, including the booster, should be administered?

Accepted Answer

2 doses

Answer

4 doses

Answer

3 doses

Answer

1 dose

Question 9

A young child presents with a low-grade fever, coryza, sore throat, a bright red rash on his cheeks, and a less intense erythematous rash on his body. Elevated IgG and IgM antibody titers to parvovirus suggest a diagnosis of which of the following?

Accepted Answer

Fifth disease

Answer

Acute Lyme disease

Answer

Possible hepatitis B infection

Answer

Possible subacute sclerosing panencephalitis (SSPE)

Question 10

A child is suffering from varicella (fever rash). The child's aunt is pregnant. When is it earliest that the child can meet her aunt?

Accepted Answer

When the lesions have crusted

Answer

Immediately

Answer

Anytime as the child is aunt's favorite

Answer

After the delivery of the baby

Infectious Diseases — MCQs

Infectious Diseases — MCQs

On this page

Practice by Chapter

Want unlimited practice?