Respiratory viruses (influenza, RSV, parainfluenza) US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Respiratory viruses (influenza, RSV, parainfluenza). These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Respiratory viruses (influenza, RSV, parainfluenza) US Medical PG Question 1: A 6-month-old infant is brought to the physician’s office by his parents due to a fever, cough, and shortness of breath. The cough is dry and has been progressively worsening for the past 48 hours along with the shortness of breath. His fever never exceeded 37.8°C (100.0°F) at home. The parents say that he has also had abundant nasal drainage and loss of appetite. He is irritable and vomited twice during this period. He has no relevant medical or family history.
His vitals are the following:
Pulse rate 165/min
Respiratory rate 77/min
Temperature 38.0°C (100.4°F)
On physical examination, there is nasal congestion with thick secretions, accompanied by nasal flaring. On chest examination, intercostal retractions are seen and diffuse wheezing on both sides are heard on auscultation. What is the most likely cause?
- A. Laryngotracheitis
- B. Asthma
- C. Rhinopharyngitis
- D. Sinusitis
- E. Bronchiolitis (Correct Answer)
Respiratory viruses (influenza, RSV, parainfluenza) Explanation: ***Bronchiolitis***
- This infant presents with **fever**, **cough**, **shortness of breath**, **tachypnea**, **nasal flaring**, **intercostal retractions**, and **wheezing**, which are classic signs of **bronchiolitis** in an infant. The dry, worsening cough and widespread wheezing further support this diagnosis.
- Bronchiolitis, often caused by **Respiratory Syncytial Virus (RSV)**, is common in infants aged 2-24 months and affects the small airways (bronchioles), leading to inflammation and obstruction.
*Laryngotracheitis*
- Laryngotracheitis, or **croup**, typically presents with a **barking, seal-like cough**, **stridor**, and hoarseness, which are not described in this case.
- It primarily affects the **larynx and trachea**, leading to upper airway obstruction, while this infant's symptoms point to lower airway involvement (wheezing).
*Asthma*
- While asthma can cause **wheezing** and **shortness of breath**, it is less common for it to present acutely with a **fever** and in a 6-month-old without prior episodes or family history of asthma.
- Asthma usually involves reversible airway obstruction and may respond to bronchodilators, differentiating it from the infectious nature of bronchiolitis.
*Rhinopharyngitis*
- Rhinopharyngitis, or the common cold, is characterized by **nasal congestion**, **sore throat**, and mild cough, but usually **does not cause significant respiratory distress**, **tachypnea**, or **wheezing** as seen in this infant.
- The severity of the respiratory symptoms, including shortness of breath and retractions, goes beyond a simple cold.
*Sinusitis*
- Sinusitis typically involves **nasal congestion**, **facial pain/pressure**, and sometimes cough due to post-nasal drip, but it is **not typically associated with widespread wheezing**, **significant shortness of breath**, or **intercostal retractions** in infants.
- While nasal drainage is present, the prominent lower respiratory symptoms point away from isolated sinusitis.
Respiratory viruses (influenza, RSV, parainfluenza) US Medical PG Question 2: A 2-year-old boy is brought to the physician by his parents for the evaluation of an unusual cough, a raspy voice, and noisy breathing for the last 2 days. During this time, the symptoms have always occurred in the late evening. The parents also report that prior to the onset of these symptoms, their son had a low-grade fever and a runny nose for 2 days. He attends daycare. His immunizations are up-to-date. His temperature is 37.8°C (100°F) and respirations are 33/min. Physical examination shows supraclavicular retractions. There is a high-pitched breath sound on inspiration. Which of the following is the most likely location of the abnormality?
- A. Epiglottis
- B. Subglottic larynx (Correct Answer)
- C. Supraglottic larynx
- D. Bronchioles
- E. Bronchi
Respiratory viruses (influenza, RSV, parainfluenza) Explanation: ***Subglottic larynx***
- The symptoms of **barking cough**, **raspy voice**, and **inspiratory stridor** (high-pitched breath sound on inspiration) are classic for **croup (laryngotracheobronchitis)**.
- Croup is characterized by **inflammation and edema of the subglottic larynx**, which is the narrowest part of the pediatric airway, leading to obstruction.
*Epiglottis*
- **Epiglottitis** typically presents with a sudden onset of **high fever**, **dysphagia**, drooling, and a muffled voice, often without a preceding viral prodrome.
- Patients with epiglottitis usually appear severely ill and may adopt a **tripod position** to maximize airway opening, which is not described here.
*Supraglottic larynx*
- While inflammation can occur here, severe **supraglottic edema** leading to the described symptoms (especially the barking cough) is uncommon in typical croup.
- Conditions affecting the supraglottic area, such as **supraglottitis**, often cause a muffled voice and severe dysphagia, rather than a raspy voice and classic croupy cough.
*Bronchioles*
- Inflammation of the bronchioles typically causes **bronchiolitis**, characterized by **wheezing**, tachypnea, and increased work of breathing due to small airway obstruction.
- This condition does not typically present with a **barking cough** or **stridor**, which are indicative of upper airway obstruction.
*Bronchi*
- Inflammation of the bronchi (**bronchitis**) primarily causes a **cough** (often productive) and sometimes wheezing or rhonchi.
- It does not typically result in **stridor** or a **raspy voice**, as these symptoms arise from laryngeal or tracheal involvement.
Respiratory viruses (influenza, RSV, parainfluenza) US Medical PG Question 3: A 72-year-old man comes to the physician with chills, nausea, and diffuse muscle aches for 3 days. His niece had similar symptoms 2 weeks ago and H1N1 influenza strain was isolated from her respiratory secretions. He received his influenza vaccination 2 months ago. His temperature is 38°C (100.4°F). A rapid influenza test is positive. Which of the following mechanisms best explains this patient's infection despite vaccination?
- A. Random point mutations within viral genome (Correct Answer)
- B. Reassortment of viral genome segments
- C. Acquisition of viral surface proteins
- D. Complementing with functional viral proteins
- E. Exchange of viral genes between chromosomes
Respiratory viruses (influenza, RSV, parainfluenza) Explanation: ***Random point mutations within viral genome***
- This patient likely contracted influenza due to **antigenic drift**, which involves **random point mutations** in the genes encoding hemagglutinin and neuraminidase, leading to minor changes in these surface antigens.
- These minor changes can allow the virus to evade the pre-existing immunity from vaccination or prior infection, even if the vaccine was received recently.
*Reassortment of viral genome segments*
- This mechanism, known as **antigenic shift**, involves the exchange of entire gene segments between different influenza strains, leading to **major changes** in surface antigens.
- While it causes pandemics, the scenario described (infection within 2 months of vaccination with H1N1) points more towards antigenic drift, which is a constant process leading to seasonal epidemics.
*Acquisition of viral surface proteins*
- Viruses do not "acquire" surface proteins from other viruses in an active process; their surface proteins are determined by their own genetic material.
- Changes in these proteins occur through mutation or reassortment, not acquisition of pre-formed proteins.
*Complementing with functional viral proteins*
- **Complementation** occurs when a defective virus is rescued by another virus providing a necessary gene product in the same host cell.
- This mechanism allows a virus to replicate but does not explain how a vaccine-induced immunity is bypassed.
*Exchange of viral genes between chromosomes*
- Influenza is an RNA virus, and its genetic material is organized into segments, not chromosomes.
- The exchange of entire gene segments (reassortment) is a known mechanism for influenza, but it would involve segments of the viral genome, not chromosomal exchange.
Respiratory viruses (influenza, RSV, parainfluenza) US Medical PG Question 4: A 61-year-old man presents to the family medicine clinic with a worsening cough for the last week. He denies hemoptysis, sputum production, shortness of breath, or upper respiratory tract symptoms. He does endorse nausea and heartburn after he eats large meals, as well as an occasional metallic taste in his mouth throughout the day. He has been diagnosed with hypertension and osteoarthritis, for which he takes lisinopril and aspirin. He has smoked half a pack of cigarettes per day since he was 20 years old. Three years ago, he had his second colonoscopy performed with normal results. His heart rate is 76/min, respiratory rate is 16/min, temperature is 37.3°C (99.2°F), and blood pressure is 148/92 mm Hg. He exhibits signs of truncal obesity. Heart auscultation reveals wide splitting of S2. Auscultation of the lungs is clear, but wheezing is noted on forced expiration. Which of the following is recommended for the patient at this time?
- A. Meningococcal vaccine
- B. Intra-articular steroid injection
- C. Hepatitis B vaccine
- D. Zoster vaccine
- E. Low-dose chest CT (Correct Answer)
Respiratory viruses (influenza, RSV, parainfluenza) Explanation: ***Low-dose chest CT***
- This patient is a 61-year-old male with a significant **smoking history** (half a pack/day since age 20 is 41 pack-years), placing him at high risk for **lung cancer**.
- **Low-dose chest CT (LDCT) screening** is recommended annually for individuals aged 50-80 with at least a **20 pack-year smoking history** who currently smoke or have quit within the past 15 years.
*Meningococcal vaccine*
- The **meningococcal vaccine** is routinely recommended for adolescents and young adults, or for specific higher-risk groups such as those with asplenia or complement deficiencies.
- This patient does not fall into a general adult population category for routine meningococcal vaccination at age 61.
*Intra-articular steroid injection*
- The patient has osteoarthritis, but his primary concern is a **worsening cough** and he has not reported increased joint pain or inflammation necessitating this treatment.
- While intra-articular steroid injections are used for osteoarthritis, they do not address the acute cough or the more pressing cancer screening need.
*Hepatitis B vaccine*
- The **Hepatitis B vaccine** is generally recommended for individuals at risk of exposure to the virus, such as healthcare workers, or those with chronic liver disease, diabetes, or HIV.
- There is no information in the patient's presentation to suggest any specific risk factors for Hepatitis B infection that would warrant vaccination at this time.
*Zoster vaccine*
- The **zoster vaccine** is recommended for adults 50 years and older to prevent shingles.
- While this patient is 61 and technically eligible for the zoster vaccine, addressing the more immediate and higher-risk concern of lung cancer screening due to his smoking history takes precedence, and the question asks for *what is recommended at this time*, implying the most urgent or relevant intervention given the clinical picture.
Respiratory viruses (influenza, RSV, parainfluenza) US Medical PG Question 5: An investigator studying viral replication isolates the genetic material of an unidentified virus strain. After exposing a cell culture to the isolated, purified viral genetic material, the cells begin to produce viral polymerase and subsequently replicate the viral genome. Infection with the investigated strain is most likely to cause which of the following conditions?
- A. Rotavirus infection
- B. Poliomyelitis (Correct Answer)
- C. Hepatitis B
- D. Rabies
- E. Influenza
Respiratory viruses (influenza, RSV, parainfluenza) Explanation: ***Poliomyelitis***
- The isolation of **purified viral genetic material** directly leading to viral protein production (polymerase) and genome replication indicates the virus has an **RNA genome that can directly serve as mRNA**.
- **Poliovirus** is a **positive-sense single-stranded RNA (+ssRNA) virus**, meaning its genome can immediately be translated by host ribosomes upon entry, acting like mRNA.
*Rotavirus infection*
- Rotavirus is a **double-stranded RNA (dsRNA) virus** and requires its own **RNA-dependent RNA polymerase** to synthesize mRNA before protein production and genome replication can occur.
- Its purified genetic material alone would not directly lead to viral protein synthesis in the absence of viral enzymes.
*Hepatitis B*
- Hepatitis B virus (HBV) is a **DNA virus** and replicates through an **RNA intermediate** via **reverse transcriptase**.
- Its genetic material cannot directly initiate the production of viral polymerase or genome replication without complex cellular machinery and viral enzymes.
*Rabies*
- Rabies virus is a **negative-sense single-stranded RNA (-ssRNA) virus**, which means its genome cannot be directly translated into protein.
- It requires its own **RNA-dependent RNA polymerase** to first synthesize complementary positive-sense mRNA strands.
*Influenza*
- Influenza virus is also a **negative-sense single-stranded RNA (-ssRNA) virus**.
- Like rabies, it carries its own **RNA-dependent RNA polymerase** to transcribe its genome into mRNA before protein synthesis can begin.
Respiratory viruses (influenza, RSV, parainfluenza) US Medical PG Question 6: A 3-year-old boy presents to an urgent care clinic with his mother. She states that his behavior has been lethargic for the past 3 days. She also notes that he has had a runny nose, mild cough, and sore throat during this time. She does not believe that he has been febrile. His temperature is 99.1°F (37.2°C), blood pressure is 105/67 mmHg, pulse is 100/min, respirations are 18/min, and SpO2 97% on room air. Which nucleic acid structure most accurately describes the most likely virus responsible for this boy’s clinical condition?
- A. Double-stranded DNA
- B. Single-stranded, negative-sense RNA
- C. Double-stranded RNA
- D. Single-stranded DNA
- E. Single-stranded, positive-sense RNA (Correct Answer)
Respiratory viruses (influenza, RSV, parainfluenza) Explanation: ***Single-stranded, positive-sense RNA***
- The constellation of a runny nose, mild cough, sore throat, and lethargy in a 3-year-old child strongly suggests a **common cold** (viral upper respiratory infection).
- The most frequent causes of the common cold are **rhinoviruses** and **coronaviruses**, both of which possess **single-stranded, positive-sense RNA genomes**.
*Double-stranded DNA*
- Viruses with double-stranded DNA genomes include **adenoviruses** and **herpesviruses**, which can cause respiratory infections but often present with more severe or distinct symptoms (e.g., adenoviral conjunctivitis, herpetic stomatitis).
- While adenoviruses can cause common cold-like symptoms, rhinoviruses and coronaviruses are statistically more prevalent in this clinical picture.
*Single-stranded, negative-sense RNA*
- Viruses with single-stranded, negative-sense RNA genomes include **influenza viruses**, **respiratory syncytial virus (RSV)**, and **paramyxoviruses**.
- While these can cause respiratory symptoms, influenza often presents with more significant **fever** and myalgia, and RSV more commonly causes **bronchiolitis** in young children.
*Double-stranded RNA*
- **Rotaviruses**, which have double-stranded RNA genomes, are primarily associated with **gastroenteritis**, causing severe diarrhea and vomiting, not typical respiratory symptoms.
- Though some reoviruses (a family of double-stranded RNA viruses) can cause respiratory illness, it is less common in this context than the positive-sense RNA viruses.
*Single-stranded DNA*
- **Parvovirus B19**, a single-stranded DNA virus, is known for causing **erythema infectiosum** (fifth disease) and aplastic crises, not general upper respiratory symptoms associated with the common cold.
- There are very few human pathogens with single-stranded DNA genomes that would cause this specific set of symptoms.
Respiratory viruses (influenza, RSV, parainfluenza) US Medical PG Question 7: A 7-month-old infant with Tetralogy of Fallot is brought to the emergency department by her parents because of a 1-day history of fever, cough, and difficulty breathing. She was born at 29 weeks of gestation. Her routine immunizations are up-to-date. She is currently in the 4th percentile for length and 2nd percentile for weight. She appears ill. Her temperature is 39.1°C (102.3°F). Physical examination shows diffuse wheezing, subcostal retractions, and bluish discoloration of the fingertips. Administration of which of the following would most likely have prevented this patient's current condition?
- A. Palivizumab (Correct Answer)
- B. Ceftriaxone
- C. Ganciclovir
- D. Ribavirin
- E. Oseltamivir
Respiratory viruses (influenza, RSV, parainfluenza) Explanation: ***Palivizumab***
* The infant's symptoms (fever, cough, wheezing, subcostal retractions) and age, especially with a history of **prematurity** and **Tetralogy of Fallot**, strongly suggest **Respiratory Syncytial Virus (RSV) bronchiolitis**.
* **Palivizumab** is a prophylactic monoclonal antibody specifically indicated for preventing severe RSV disease in high-risk infants, including those born prematurely or with significant congenital heart disease.
* *Ceftriaxone*
* **Ceftriaxone** is an antibiotic used to treat bacterial infections, and the patient's presentation is more consistent with a viral respiratory illness.
* While bacterial superinfection can occur, ceftriaxone would not prevent the primary viral infection.
* *Ganciclovir*
* **Ganciclovir** is an antiviral medication used to treat **Cytomegalovirus (CMV)** infections, which typically present differently from RSV bronchiolitis.
* There is no indication of CMV infection in this patient's clinical picture.
* *Ribavirin*
* **Ribavirin** is an antiviral sometimes used to treat severe RSV infections in specific high-risk populations, but it is not a prophylactic agent and its use is limited due to toxicity.
* It would not have prevented the initial infection.
* *Oseltamivir*
* **Oseltamivir** is an antiviral medication used to treat **influenza virus** infections.
* The clinical presentation, particularly the diffuse wheezing and commonality in infants, is more characteristic of RSV than influenza.
Respiratory viruses (influenza, RSV, parainfluenza) US Medical PG Question 8: A scientist is studying the influenza A virus. He focuses on two strains – one from humans (H7N1) and one from horses (H3N8). He takes cells from chickens and coinfects these cells with both influenza strains. From these chicken cells, the scientist isolates a new strain and finds that this new strain can infect human cells. He further characterizes the new strain’s hemagglutinin and neuraminidase description as H7N8. What term best describes the process that underlies these experimental results?
- A. Transduction
- B. Antigenic drift
- C. Transformation
- D. Conjugation
- E. Antigenic shift (Correct Answer)
Respiratory viruses (influenza, RSV, parainfluenza) Explanation: ***Antigenic shift***
- **Antigenic shift** in influenza viruses refers to the process where two different influenza strains **coinfect** the same host cell, leading to a **reassortment** of their segmented genomes.
- This reassortment creates a novel viral strain with a new combination of hemagglutinin (H) and neuraminidase (N) antigens (e.g., H7N1 + H3N8 → H7N8), which can lead to pandemics.
*Transduction*
- **Transduction** is a process where foreign DNA is introduced into a cell by a virus or viral vector, primarily seen in bacteria.
- It involves the transfer of genetic material via **bacteriophages** and does not describe the reassortment of influenza virus segments.
*Antigenic drift*
- **Antigenic drift** involves small, gradual changes in the H and N antigens of influenza viruses due to **point mutations** during replication.
- These slow mutations lead to seasonal epidemics, but not the creation of a completely new subtype as described.
*Transformation*
- **Transformation** is the process by which a cell takes up naked DNA from its environment, incorporating it into its own genome.
- This mechanism is common in bacteria for acquiring new genetic traits and is not applicable to the reassortment of viral segments within a coinfected host cell.
*Conjugation*
- **Conjugation** is a process of genetic material transfer between bacteria through direct cell-to-cell contact, typically via a **pilus**.
- This mechanism is distinct from viral genetic reassortment and does not involve the coinfection of a host cell by different viral strains.
Respiratory viruses (influenza, RSV, parainfluenza) US Medical PG Question 9: A scientist performed an experiment to produce hybrid viruses by mixing two different serotypes of influenza virus, H1N1 and H2N2, in a respiratory epithelium cell line. Several days later, the scientist collected the media and analyzed the viral progeny. She found the following serotypes of virus: H1N1, H2N2, H1N2, and H2N1. Which of the following terms best explains the appearance of new serotypes?
- A. Phenotypic mixing
- B. Complementation
- C. Reassortment (Correct Answer)
- D. Transformation
- E. Recombination
Respiratory viruses (influenza, RSV, parainfluenza) Explanation: ***Reassortment***
- **Reassortment** occurs in viruses with **segmented genomes**, like influenza, when a host cell is co-infected with two different viral strains.
- During replication, the progeny viruses can package segments from either parent, leading to novel combinations of surface proteins (**H** and **N** antigens), as seen with the emergence of H1N2 and H2N1.
*Phenotypic mixing*
- **Phenotypic mixing** involves the packaging of the genome of one virus into the capsid or envelope proteins derived from another virus, without genetic exchange.
- While progeny viruses might temporarily display characteristics of both parents, their genetic material remains unchanged, so subsequent generations would revert to the original serotype unless continuous co-infection occurs.
*Complementation*
- **Complementation** happens when one virus provides a functional protein that is deficient in another co-infecting virus, allowing the deficient virus to replicate.
- This process does not lead to the formation of new hybrid serotypes but rather allows a 'defective' virus to replicate alongside a 'helper' virus.
*Transformation*
- **Transformation** in microbiology typically refers to the uptake of foreign genetic material (DNA) by a bacterial cell, altering its genetic makeup.
- In virology, it can also refer to the process by which some viruses induce uncontrolled cell growth in eukaryotic cells, leading to oncogenesis, which is unrelated to the formation of hybrid serotypes.
*Recombination*
- **Recombination** involves the exchange of genetic material between two homologous chromosomes or DNA molecules, leading to a new genetic sequence.
- While it results in new genetic combinations, the term **reassortment** is specifically used for the exchange of entire genome segments characteristic of viruses like influenza.
Respiratory viruses (influenza, RSV, parainfluenza) US Medical PG Question 10: An investigator studying influenza virus variability isolates several distinct influenza virus strains from the respiratory secretions of a study subject. Mass spectrometry analysis of one strain shows that it expresses neuraminidase on its surface. Subsequent sequencing of this strain shows that its genome lacks the neuraminidase gene. Which of the following is the most likely explanation for this finding?
- A. Complementation
- B. Recombination
- C. Transduction
- D. Phenotypic mixing (Correct Answer)
- E. Reassortment
Respiratory viruses (influenza, RSV, parainfluenza) Explanation: ***Phenotypic mixing***
- **Phenotypic mixing** occurs when a virus genome is packaged into a capsid or envelope proteins derived from a *different* but co-infecting virus. In this case, the influenza strain's genome lacks the **neuraminidase gene**, but it expresses neuraminidase on its surface because it acquired the protein from another co-infecting strain.
- This process is temporary, as the progeny of this mixed virus will replicate normally according to its own **genome**, and thus would not express neuraminidase unless it also inherited the gene.
*Complementation*
- **Complementation** occurs when two viruses infect the same cell, and one virus provides a **gene product** (a protein) that the other virus, which has a defective gene, needs to replicate.
- In complementation, the defective virus *replicates its own genome*, but uses the protein supplied by the other virus; it would not express a protein derived directly from another virus's genome on its surface if its own genome did not encode it.
*Recombination*
- **Recombination** involves the exchange of genetic material between two different but related viruses, resulting in a **hybrid genome** containing genes from both parental viruses.
- If recombination had occurred, the virus's genome *would* contain the neuraminidase gene, which is contradicted by the finding that the genome *lacks* it.
*Transduction*
- **Transduction** is a process where **bacteriophages** (viruses that infect bacteria) transfer bacterial DNA from one bacterium to another. This mechanism is specific to bacteria and their phages, and is not applicable to human influenza viruses.
- This process involves the transfer of genetic material between bacteria via a viral vector, which is unrelated to the expression of a surface protein from a *non-encoded gene* in influenza.
*Reassortment*
- **Reassortment** is a unique characteristic of viruses with **segmented genomes**, such as influenza, where segments can be exchanged between different strains during co-infection.
- If reassortment had occurred, the influenza strain's genome *would have acquired* the neuraminidase gene segment, which contradicts the finding that the genome *lacks* the neuraminidase gene.
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