A 11-month old child presents with complaints of respiratory distress. On examination there is bilateral crepitation and wheezing. Which of the following is the most likely cause?

Respiratory syncytial virus (RSV) is the most impoant cause of pneumonia and bronchiolitis in infants. The classic disease is bronchiolitis, characterized by diffuse wheezing, variable fever, cough, tachypnea, difficulty feeding, and, in severe cases, cyanosis. In severe cases, children must be hospitalized and given humidified oxygen. Ref: Levinson W. (2012). Chapter 39. RNA-Enveloped Viruses. In W. Levinson (Ed), Review of Medical Microbiology & Immunology, 12e.