Infectious Diseases Practice Questions

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.

Q: An 8-month-old girl presented with sudden onset of high fever (103 extdegree F). Despite the absence of signs of upper respiratory tract infection, meningitis, or encephalitis, her fever escalated to 105 extdegree F, leading to a febrile seizure. Upon examination by the pediatrician, the child's temperature had subsided, and a generalized papular rash was noted. What is the most likely diagnosis?

Roseola infantum caused by human herpes virus 6. ### Explanation The clinical presentation described is classic for **Roseola Infantum** (also known as Exanthem Subitum or Sixth Disease). **1. Why the Correct Answer is Right:** Roseola infantum, caused primarily by **Human Herpesvirus 6 (HHV-6)**, typically affects infants aged 6–15 months. The hallmark of this condition is a **sudden high fever** (often >103°F) lasting 3–5 days in an otherwise well-appearing child. As the fever abruptly subsides (**defervescence**), a rose-pink, maculopapular rash appears, starting on the trunk and spreading to the face and extremities. The rapid rise in temperature makes Roseola the most common cause of **febrile seizures** in this age group. **2. Why Other Options are Incorrect:** * **Erythema Infectiosum (Parvovirus B19):** Characterized by a "slapped-cheek" appearance followed by a reticular (lace-like) rash on the body. It lacks the preceding high fever and sudden defervescence pattern. * **Hand-Foot-and-Mouth Disease (Coxsackievirus A16):** Presents with vesicular eruptions on the palms, soles, and oral mucosa (herpangina), rather than a generalized post-febrile papular rash. * **Measles (Morbillivirus):** Presents with the "3 Cs" (Cough, Coryza, Conjunctivitis) and Koplik spots. Crucially, in measles, the rash appears **while the fever is at its peak**, not after it disappears. **3. NEET-PG High-Yield Pearls:** * **Nagayama Spots:** Erythematous papules on the soft palate and uvula seen in some Roseola patients. * **HHV-6 Pathogenesis:** It infects T-lymphocytes (CD4+ cells). * **Sequence is Key:** Fever **THEN** Rash = Roseola. Fever **WITH** Rash = Measles/Rubella. * **Treatment:** Supportive; ganciclovir is reserved only for severe immunocompromised cases.

Q: What is the most fatal complication of measles?

Subacute sclerosing panencephalitis (SSPE). **Explanation:** The correct answer is **Subacute sclerosing panencephalitis (SSPE)**. SSPE is a rare, progressive, and chronic inflammatory neurological disease caused by a persistent infection with a mutant strain of the measles virus. It typically manifests **7–10 years** after the initial measles infection. It is considered the **most fatal complication** because it is universally lethal; there is no known cure, and it leads to progressive cognitive decline, myoclonic jerks, and eventually death. **Analysis of Incorrect Options:** * **Pneumonia:** This is the **most common cause of death** from measles in children and the most common overall complication. However, while it causes more total deaths due to its frequency, it is not as "fatal" (in terms of case-fatality rate) as SSPE, which has a 100% mortality rate. * **Otitis Media:** This is the **most common complication** of measles overall, but it is rarely life-threatening. * **Polyps:** These are not a recognized complication of measles infection. **NEET-PG High-Yield Pearls:** * **Most common complication:** Otitis media. * **Most common cause of death:** Pneumonia (Hecht’s Giant Cell Pneumonia). * **SSPE Diagnosis:** Look for high titers of anti-measles antibodies in the CSF and serum (intrathecal synthesis) and **periodic complexes** on EEG. * **Vitamin A:** Supplementation reduces the severity and mortality of measles in children. * **Koplik spots:** Pathognomonic enanthem found on the buccal mucosa opposite the lower second molars during the pre-eruptive stage.

Q: An 8-year-old boy presented with a 4-day history of swelling on both sides of the face, below the ears. The swelling first started on the left side and then appeared on the right side 3 days later. What is the most likely diagnosis?

Epidemic parotitis. **Explanation:** The clinical presentation of an 8-year-old child with acute, sequential, bilateral swelling of the parotid glands (below the ears) is classic for **Epidemic Parotitis**, commonly known as **Mumps**. **Why the correct answer is right:** Mumps is a viral infection caused by the *Rubulavirus* (Paramyxoviridae family). It typically affects children and is characterized by a prodrome of fever and malaise, followed by parotid swelling. A key diagnostic feature is the **asymmetrical progression**: it often starts on one side and involves the contralateral side within 2–3 days. The swelling displaces the earlobe upward and outward, which matches the description in the question. **Why incorrect options are wrong:** * **Bacterial Sialadenitis:** Usually presents as a **unilateral**, extremely painful, erythematous swelling. It is often associated with purulent discharge from Stensen’s duct and high-grade fever, unlike the typical viral course of Mumps. * **Sialadenosis:** This refers to non-inflammatory, non-neoplastic enlargement of the salivary glands, usually associated with systemic conditions like diabetes, alcoholism, or malnutrition. It is chronic and painless, not acute. * **Sialadenitis:** This is a general term for inflammation of the salivary gland. While Mumps is a form of viral sialadenitis, "Epidemic Parotitis" is the specific clinical diagnosis for this presentation in a pediatric population. **Clinical Pearls for NEET-PG:** * **Most common complication in children:** Aseptic meningitis. * **Most common complication in post-pubertal males:** Orchitis (usually unilateral; rarely leads to infertility). * **Diagnosis:** Primarily clinical; confirmed by IgM antibodies or PCR. * **Amylase:** Serum amylase levels are often elevated in Mumps due to salivary gland involvement. * **Prevention:** Live attenuated vaccine (MMR/MMRV).

Question 1

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 2

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 3

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 4

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 5

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 6

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

Question 7

Epiglottitis is diagnosed in a 4-year-old unvaccinated child presenting at home. What is the appropriate management step?

Accepted Answer

Ampicillin for 4 days

Answer

Vaccination

Answer

Rifampin for 4 days

Answer

Doxycycline

Question 8

An 8-month-old girl presented with sudden onset of high fever (103	extdegree F). Despite the absence of signs of upper respiratory tract infection, meningitis, or encephalitis, her fever escalated to 105	extdegree F, leading to a febrile seizure. Upon examination by the pediatrician, the child's temperature had subsided, and a generalized papular rash was noted. What is the most likely diagnosis?

Accepted Answer

Roseola infantum caused by human herpes virus 6

Answer

Erythema infectiosum caused by parvovirus B19

Answer

Hand-foot-and-mouth disease caused by Coxsackievirus A

Answer

Measles caused by Morbillivirus

Question 9

What is the most fatal complication of measles?

Accepted Answer

Subacute sclerosing panencephalitis (SSPE)

Answer

Pneumonia

Answer

Polyps

Answer

Otitis media

Question 10

An 8-year-old boy presented with a 4-day history of swelling on both sides of the face, below the ears. The swelling first started on the left side and then appeared on the right side 3 days later. What is the most likely diagnosis?

Accepted Answer

Epidemic parotitis

Answer

Bacterial sialadenitis

Answer

Sialadenosis

Answer

Sialadenitis

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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