Treatment and clinical time course of study subjects.

*Wheezing was defined as a continuous high pitched sound emitting from the chest during expiration on auscultation.†Pneumonia was diagnosed on the basis of infiltrative shadows on chest radiograph.‡Antiviral medication was switched oseltamivir to zanamivire and vice versa.§The dose of corticosteroid was equivalent to methylprednisolone 1.0–1.5 mg/body weight (kg)/time, 2–4 times/day, in subjects under 15 years of age, and 40–80 mg/time, 2–4 times/day in those over 15 years of age.¶At least one medication of shortacting β2-agonist, longacting β2-agonist, inhaled isoproterenol, inhaled disodium cromoglycate, aminophylline, and leukotriene receptor antagonists.∥Oxygen was administered using a nasal cannula or face mask.**Antibiotics.