An 11 month old girl has a fever and cough for 6 days. Her clinical status suddently worsens with increased coughing after choking on a carrot. She presents in severe respiratory distress with indrawing, and is very lethargic.

Her RR=100, O2 stats = 70% (on room air), HR = 140

Family members all have URTI symptoms, family history positive for asthma.

Based on the above history, what is your differential diagnosis?