PLE-4683

An 18 year old male came in for complaints of cough and watery nasal discharges 1 week PT.Upon examination at the ER, T = 38.5C, RR = 65, dyspnea and difficulty to console the child. After 1 hour, pulse oximetry revealed 70% thus patient was intubated. Auscultation of chest revealed fine crackles on both lung fields with occasional wheezes. CBC taken was normal. CXR revealed hyperinflation and air trapping. Which of the following is the most likely diagnosis?