Viral Infections USMLE Step 1 Practice Question
A 6-year-old boy is brought to the emergency department with a 3-day history of progressive cough and dyspnea. His mother reports he has been wheezing and has had low-grade fevers. Vital signs show: temperature 39.1°C, heart rate 120/min, respiratory rate 34/min, oxygen saturation 87% on room air, and blood pressure 102/65 mmHg. On examination, you appreciate subcostal and intercostal retractions with diffuse wheezing and fine crackles on auscultation. A chest X-ray demonstrates hyperinflation with bilateral interstitial infiltrates. Nasopharyngeal swab with immunofluorescence microscopy shows multinucleated giant cells. Complete blood count reveals lymphocytic predominance with normal white blood cell count. The patient attends daycare and has no recent travel history. Which of the following is the most likely diagnosis?
Answer choices
- AAdenovirus pneumonia with bronchial obstruction
- BInfluenza A with secondary bacterial superinfection
- CRespiratory syncytial virus (RSV) bronchiolitisCorrect answer
- DParainfluenza virus with laryngotracheobronchitis
- EHuman metapneumovirus with atypical pneumonia
- FRhinovirus acute asthma exacerbation
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.