The index patient was an otherwise healthy boy aged 6 years. The boy and his family attended a gathering with relatives at the motel on December 25, 2006, and he spent approximately 3 hours swimming in the pool. During this time, he had onset of coughing and dyspnea. He stopped playing in the pool but continued to cough, with one or two episodes of posttussive emesis. His parents had intended to spend the night at the motel but checked out early and returned to their home (approximately 15 miles away) the evening of December 25. During a period of 5 hours, the boy's condition worsened. He became agitated and more dyspneic and was taken to a local emergency department (ED) with erythematous eyes and nasopharynx, a barking cough, inspiratory stridor, expiratory wheezes, and respiratory distress. The parents told the physician that multiple persons in their group had developed burning eyes, nasal burning, congestion, and cough. Physical examination of the boy indicated croupy cough, stridor at rest, and moderate retractions. Oxygen saturation level was 98% on room air; lungs were clear on auscultation, and no chest radiograph was performed. In the ED, he received a dexamethasone injection, 3 doses of racemic epinephrine, and cool-mist respiratory therapy. He was transferred to the pediatric intensive care unit in stable condition for observation, with a guarded prognosis and a diagnosis of upper airway obstruction from chemical epiglottitis and laryngotracheobronchitis; drug therapy was discontinued, and no additional treatments were administered. The boy's condition gradually improved, and he was discharged the next morning. The attending physician recorded chlorine irritation as the cause of illness.