What condition is most likely in an infant with fever and both inspiratory and expiratory wheezing, but no history of reactive airway disease?

In this scenario, the presence of fever coupled with both inspiratory and expiratory wheezing in an infant, who doesn't have a history of reactive airway disease, strongly indicates bronchiolitis. This condition is typically caused by a viral infection, most commonly respiratory syncytial virus (RSV), affecting the small airways (bronchioles) in infants and very young children.

Bronchiolitis typically presents with wheezing (both inspiratory and expiratory), cough, and signs of respiratory distress along with a fever. The acute illness often manifests in infants younger than two years old and can include a history of upper respiratory infection symptoms preceding the more severe wheezing.

Despite other options being considered, they do not align as closely with the clinical picture presented. Tracheobronchitis would generally present with a more severe cough and usually some form of upper respiratory tract involvement without significant lower airway wheezing. Croup is characterized primarily by inspiratory stridor and a "barking" cough, rather than both types of wheezing. The presence of a foreign body typically would suggest unilateral wheezing or localized symptoms, which would not account for the bilateral wheezing and fever seen in this case.

Therefore, the combination of fever and