Viral Infections USMLE Step 1 Practice Question
A 72-year-old man with COPD presents to the emergency department with a 5-day history of progressive dyspnea, productive cough with purulent sputum, and fever. Vital signs show temperature 38.8°C, heart rate 108/min, respiratory rate 22/min, blood pressure 142/88 mmHg, and oxygen saturation 88% on room air. Chest X-ray demonstrates bilateral lower lobe consolidations. Laboratory studies show WBC 14,200/μL and sputum culture positive for Streptococcus pneumoniae. A rapid influenza antigen test from a nasopharyngeal swab returns positive. The patient denies recent antibiotic use and reports that his grandchildren visited 1 week ago with upper respiratory symptoms. Which of the following best explains the pathophysiologic basis for this patient's concurrent influenza and pneumococcal infection?
Answer choices
- AInfluenza virus damages respiratory epithelium and impairs mucociliary clearance, facilitating secondary bacterial invasionCorrect answer
- BStreptococcus pneumoniae produces viral neuraminidase, allowing it to mimic influenza infection
- CThe patient's COPD prevents the immune system from controlling either pathogen independently
- DInfluenza-specific IgG antibodies cross-react with pneumococcal antigens, worsening bacterial proliferation
- EThe rapid influenza test demonstrates a false positive due to molecular mimicry with pneumococcal antigens
- FInfluenza infection directly inhibits bacterial phagocytosis by neutrophils, preventing pneumococcal clearance
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