Santos replies: The factors that contributed to the increased rate of H1N1 transmission in the emergency department (ED) setting are multifaceted. Infection control practices likely played a large role in the spread of H1N1 in EDs. Universal precautions may be difficult to always comply with because of the severe time restraints, the large degree of patient contact, and the simultaneous management of multiple patients with which ED personnel are challenged. In addition, because transmission of H1N1 occurs through both respiratory and aerosol transmission, EDs are at a higher risk due to the many aerosol-producing procedures that are performed there. For example, EDs commonly perform diagnostic sputum collection, airway suctioning, and endotracheal intubation, and administer nebulized medications, bronchoscopy, and ventilation procedures. These factors, compounded with ED overcrowding likely contributed to the high rate of H1N1 infection in the ED setting.