Infectious Diseases Practice Questions

Q: A 1-year-old child is brought in for routine vaccination. Which of the following vaccines is typically administered at this age to provide immunity against multiple diseases?

MMR vaccine. ***MMR vaccine*** - The **Measles, Mumps, and Rubella (MMR) vaccine** is typically recommended for administration at **9-12 months of age** (first dose at 9 months as per IAP schedule, or 12-15 months as per WHO/CDC) as part of routine childhood immunizations. - It provides protection against **three common childhood diseases** (measles, mumps, and rubella) with a single shot. - This is the **primary multi-disease vaccine** given at this age. *BCG vaccine* - The **Bacillus Calmette-Guérin (BCG) vaccine** primarily protects against **tuberculosis** and is typically given **at birth** as per the Indian immunization schedule. - It is not a multi-disease vaccine and is not administered at 1 year of age. *Hepatitis B vaccine* - The **Hepatitis B vaccine** is administered in a **series**, with the first dose given at **birth**, followed by doses at 6, 10, and 14 weeks of age. - It specifically targets the **Hepatitis B virus** only and is not a multi-disease vaccine given at 1 year. *Influenza vaccine* - The **influenza vaccine** is recommended **annually** starting at **6 months of age**, but it targets **seasonal influenza strains** only. - It is not considered a routine multi-disease vaccine like MMR for childhood immunization.

Q: Which condition is characterized by a "slapped cheek" appearance in children?

Fifth disease. ***Fifth disease*** - Also known as **Erythema infectiosum**, this viral illness is caused by **Parvovirus B19** and classically presents with a distinctive erythematous rash on the cheeks, giving a **"slapped cheek" appearance**. - Following the facial rash, a **lacy, reticular rash** typically appears on the trunk and extremities. *Scarlet fever* - Characterized by a **fine, sandpaper-like rash** that starts on the neck and chest and spreads throughout the body, often sparing the area around the mouth (circumoral pallor). - It is caused by **Streptococcus pyogenes** and is associated with a **strawberry tongue** and fever. *Kawasaki disease* - An acute systemic vasculitis primarily affecting young children, presenting with prolonged fever, **conjunctivitis**, **oral mucosal changes** (strawberry tongue, red cracked lips), **rash**, and **cervical lymphadenopathy**. - It does not typically cause a "slapped cheek" rash. *Measles* - Characterized by a **maculopapular rash** that typically starts on the face and behind the ears, then spreads downwards. - Prior to the rash, **Koplik spots** (small white spots on the buccal mucosa) are pathognomonic.

Q: A 5-year-old boy presents with a rash that began on his face and has spread to his trunk and limbs. The rash consists of red patches that give a 'slapped cheek' appearance on the face, followed by a lacy, net-like rash on the trunk and limbs, and he also has a low-grade fever. What is the most likely diagnosis?

Erythema Infectiosum. ***Erythema Infectiosum*** - The distinctive **'slapped cheek' rash** on the face, followed by a **lacy, reticular (net-like) rash** spreading to the trunk and limbs, is characteristic of Erythema Infectiosum, also known as Fifth Disease, caused by **Parvovirus B19**. - It often presents with a **low-grade fever** and is more common in school-aged children. *Scarlet Fever* - Characterized by a **fine, sandpaper-like rash** that blanches with pressure and often starts on the neck and chest before spreading. - Typically accompanied by a **high fever**, sore throat, and swollen lymph nodes, due to a **Group A Streptococcus** infection. *Measles* - Measles rash typically presents as **maculopapular, erythematous lesions** that start behind the ears and on the face, spreading downwards. - It is preceded by **Koplik spots** (small white spots on the buccal mucosa) and a prodrome of high fever, cough, conjunctivitis, and coryza. *Roseola* - Roseola is characterized by a **high fever** (often >103°F) that lasts for 3-5 days, followed by the sudden appearance of a **rose-pink maculopapular rash** once the fever breaks. - The rash usually starts on the trunk and spreads to the neck and extremities, but does not present with a "slapped cheek" or lacy appearance.

Q: A 6-month-old infant is brought to the clinic with a history of severe cough. Upon examination, the child exhibits severe respiratory distress and is diagnosed with pertussis. Which vaccine is recommended for prevention?

Subunit. ***Subunit*** - The **pertussis vaccine** (DTaP for infants/children and Tdap for adolescents/adults) is a **subunit vaccine**, meaning it contains only specific purified antigens from the *Bordetella pertussis* bacterium, such as pertussis toxin, filamentous hemagglutinin, and pertactin. - This type of vaccine is used because the whole-cell pertussis vaccine (DTP) was associated with a higher rate of adverse effects, leading to the development of safer acellular subunit formulations. *Live attenuated* - **Live attenuated vaccines** contain a weakened form of the pathogen that can replicate in the host without causing severe disease, providing a strong immune response (e.g., MMR, varicella, rotavirus). - While effective, live attenuated vaccines are generally not used for pertussis due to concerns about safety and potential for reversion to virulence in some cases. *Inactivated* - **Inactivated vaccines** contain whole pathogens that have been killed or inactivated, preventing them from replicating but retaining their antigenicity (e.g., inactivated polio vaccine, influenza vaccine). - While one of the older pertussis vaccines (DTP) was a **whole-cell inactivated vaccine**, the current recommended DTaP/Tdap vaccines are **acellular subunit vaccines**, which are safer due to fewer adverse reactions. *Conjugate* - **Conjugate vaccines** are created by chemically linking a polysaccharide antigen (which is T-cell independent) to a protein carrier (which is T-cell dependent), thereby eliciting a more robust and long-lasting immune response, especially in infants (e.g., Hib, pneumococcal, meningococcal vaccines). - The pertussis vaccine is not a conjugate vaccine; its antigens are primarily proteins (e.g., pertussis toxin), not polysaccharides conjugated to a carrier protein.

Q: Which of the following is the most common cause of pneumonia in a 2-year-old child?

Streptococcus pneumoniae. ***Streptococcus pneumoniae*** - **Streptococcus pneumoniae** is the **most common cause of bacterial pneumonia** in children aged 2 months to 5 years, including 2-year-olds. - Remains the leading bacterial pathogen causing community-acquired pneumonia in this age group despite pneumococcal vaccination. - Typically presents with **lobar pneumonia**, high fever, and may be associated with **pleural effusion** or empyema in severe cases. - The **13-valent pneumococcal conjugate vaccine (PCV13)** has reduced incidence but S. pneumoniae remains the predominant bacterial cause. *RSV* - **Respiratory Syncytial Virus (RSV)** is the most common cause of **bronchiolitis** and lower respiratory tract infections in **infants**, particularly those aged **2-8 months**. - By age 2 years, RSV remains a cause of viral pneumonia but is significantly less common than in infancy. - When it does occur at this age, it tends to be less severe than in younger infants. *Haemophilus influenzae* - **Non-typeable Haemophilus influenzae** can cause pneumonia but is less common than S. pneumoniae. - **Haemophilus influenzae type b (Hib)** vaccine has dramatically reduced invasive Hib disease, including pneumonia. - Now accounts for a much smaller proportion of childhood pneumonia cases in vaccinated populations. *Mycoplasma pneumoniae* - **Mycoplasma pneumoniae** is a common cause of **atypical pneumonia** in **school-aged children** (>5 years) and adolescents. - Uncommon in children under 5 years of age, though can occasionally occur. - Presents with gradual onset, dry cough, and extrapulmonary manifestations (rash, myalgias).

Q: What is the next best step in managing a child presenting with fever and metaphyseal bone pain, suspected of having acute osteomyelitis?

Start empirical antibiotics immediately. ***Start empirical antibiotics immediately*** - In a child with suspected **acute osteomyelitis**, prompt initiation of empirical antibiotics is crucial to prevent further bone destruction and systemic spread of infection. - Waiting for culture results or extensive imaging can delay treatment, leading to worse outcomes, including **septic arthritis** or chronic osteomyelitis. *Obtain a blood culture and perform imaging* - While **blood cultures** and **imaging** (such as X-rays, ultrasound, or MRI) are essential diagnostic steps, they should be performed concurrently with, or immediately after, the initiation of empirical antibiotics. - Imaging confirms the diagnosis and extent, while cultures identify the causative organism, but neither should delay the initial therapeutic intervention. *Wait for MRI results before starting treatment* - **Magnetic Resonance Imaging (MRI)** is highly sensitive for diagnosing osteomyelitis, but waiting for MRI results can cause a significant delay in treatment, especially in an acute setting. - This delay increases the risk of complications such as **bone damage** or spread of infection. *Conduct a bone biopsy immediately* - A **bone biopsy** provides definitive diagnosis and allows for targeted antibiotic therapy based on culture results, but it is an invasive procedure and not the immediate first step. - It is typically reserved for cases where initial empirical antibiotic therapy fails or the diagnosis remains uncertain despite other diagnostic tests.

Q: A 7-year-old girl presents with a sore throat, fever, and a strawberry tongue. Which of the following conditions is most likely?

Scarlet fever. ***Scarlet fever*** - The classic triad of **sore throat**, **fever**, and **strawberry tongue** is highly characteristic of scarlet fever, a systemic illness caused by toxigenic strains of **Group A Streptococcus**. - Other common findings include a **scarlatiniform rash** (sandpaper-like texture) and **circumoral pallor**. *Kawasaki disease* - While it can present with fever and strawberry tongue, Kawasaki disease typically involves **bilateral conjunctival injection**, **polymorphous rash**, **cervical lymphadenopathy**, and changes in **extremities** (e.g., desquamation). - It usually occurs in children younger than 5 years and lacks the prominent pharyngitis associated with scarlet fever. *Infectious mononucleosis* - Caused by the **Epstein-Barr virus**, it is characterized by **fever**, **pharyngitis**, **lymphadenopathy**, and sometimes **splenomegaly**. - A strawberry tongue is not a typical feature, and the pharyngitis is often exudative. *Hand-foot-and-mouth disease* - This viral illness, often caused by **Coxsackievirus**, presents with **fever**, **oral lesions** (herpangina-like), and a characteristic rash on the **hands and feet** (vesicular or papular). - A strawberry tongue is not a typical or distinguishing feature of hand-foot-and-mouth disease.

Q: A 3-year-old child presents with a history of high fever, irritability, and refusal to move the right hip. What is the most likely diagnosis?

Septic arthritis. ***Septic arthritis*** - The combination of **high fever, irritability, and refusal to move the hip** in a 3-year-old child is highly suggestive of **septic arthritis**, a medical emergency [1]. - This condition involves an **infection within the joint space**, leading to severe pain and limited range of motion due to inflammation and pus accumulation [2]. *Transient synovitis* - While it causes hip pain and refusal to bear weight, **transient synovitis** typically presents with a **lower-grade or no fever** and less severe systemic symptoms [2]. - It is a self-limiting inflammation of the hip joint that usually follows a **viral infection**. *Legg-Calvé-Perthes disease* - This condition is characterized by **avascular necrosis of the femoral head** and typically presents with a **limp** and **insidious onset of hip pain**, usually without fever or acute irritability. - It usually affects children between 4 and 8 years old, and **fever is generally absent**. *Slipped capital femoral epiphysis* - This condition occurs when the **femoral head slips off the femoral neck** through the growth plate and is more common in **adolescents (typically 10-16 years)**, particularly during periods of rapid growth [1]. - It usually presents with **hip or knee pain and a limp** but generally **without fever**.

Q: Which viral infection is associated with Koplik spots and a maculopapular rash?

Measles. ***Measles*** - **Koplik spots** are pathognomonic for measles, appearing as small, white spots on a red background on the buccal mucosa. - The **maculopapular rash** of measles typically starts on the face and behind the ears, then spreads downwards to the trunk and extremities. *Rubella* - While rubella presents with a **maculopapular rash**, it does not cause Koplik spots. - The rubella rash is usually fainter and clears more rapidly than measles. *Varicella* - Varicella, or **chickenpox**, is characterized by a vesicular rash that progresses from macules to papules, vesicles, and scabs. - It does not present with Koplik spots or a typical maculopapular rash. *Cytomegalovirus* - CMV infection can cause a variety of symptoms, including fever, fatigue, and sometimes a rash, especially in immunocompromised individuals. - It is not associated with either Koplik spots or a characteristic maculopapular rash.

Question 1

A 1-year-old child is brought in for routine vaccination. Which of the following vaccines is typically administered at this age to provide immunity against multiple diseases?

Accepted Answer

MMR vaccine

Answer

BCG vaccine

Answer

Hepatitis B vaccine

Answer

Influenza vaccine

Question 2

Which condition is characterized by a "slapped cheek" appearance in children?

Accepted Answer

Fifth disease

Answer

Scarlet fever

Answer

Kawasaki disease

Answer

Measles

Question 3

A 5-year-old boy presents with a rash that began on his face and has spread to his trunk and limbs. The rash consists of red patches that give a 'slapped cheek' appearance on the face, followed by a lacy, net-like rash on the trunk and limbs, and he also has a low-grade fever. What is the most likely diagnosis?

Accepted Answer

Erythema Infectiosum

Answer

Scarlet Fever

Answer

Measles

Answer

Roseola

Question 4

A 6-month-old infant is brought to the clinic with a history of severe cough. Upon examination, the child exhibits severe respiratory distress and is diagnosed with pertussis. Which vaccine is recommended for prevention?

Accepted Answer

Subunit

Answer

Live attenuated

Answer

Conjugate

Answer

Inactivated

Question 5

Which of the following is the most common cause of pneumonia in a 2-year-old child?

Accepted Answer

Streptococcus pneumoniae

Answer

Haemophilus influenzae

Answer

Mycoplasma pneumoniae

Answer

RSV

Question 6

What is the next best step in managing a child presenting with fever and metaphyseal bone pain, suspected of having acute osteomyelitis?

Accepted Answer

Start empirical antibiotics immediately

Answer

Wait for MRI results before starting treatment

Answer

Conduct a bone biopsy immediately

Answer

Obtain a blood culture and perform imaging

Question 7

A 7-year-old girl presents with a sore throat, fever, and a strawberry tongue. Which of the following conditions is most likely?

Accepted Answer

Scarlet fever

Answer

Kawasaki disease

Answer

Infectious mononucleosis

Answer

Hand-foot-and-mouth disease

Question 8

A 3-year-old child presents with a history of high fever, irritability, and refusal to move the right hip. What is the most likely diagnosis?

Accepted Answer

Septic arthritis

Answer

Transient synovitis

Answer

Legg-Calvé-Perthes disease

Answer

Slipped capital femoral epiphysis

Question 9

A 2-month-old infant presents with poor feeding, irritability, and a bulging anterior fontanelle. What is the most likely diagnosis?

Accepted Answer

Meningitis

Answer

Hydrocephalus

Answer

Intraventricular Hemorrhage

Answer

Cerebral Palsy

Question 10

Which viral infection is associated with Koplik spots and a maculopapular rash?

Accepted Answer

Measles

Answer

Rubella

Answer

Varicella

Answer

Cytomegalovirus

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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