Health information exchange, biosurveillance efforts, and emergency department crowding during the spring 2009 H1N1 outbreak in New York City.

Novel H1N1 influenza spread rapidly around the world in spring 2009. Few places were as widely affected as the New York metropolitan area. Emergency departments (EDs) in the region experienced daily visit increases in 2 distinct temporal peaks, with means of 36.8% and 60.7% over baseline in April and May, respectively, and became, in a sense, the "canary in the coal mine" for the rest of the country as we braced ourselves for resurgent spread in the fall. Biosurveillance efforts by public health agencies can lead to earlier detection, potentially forestalling spread of outbreaks and leading to better situational awareness by frontline medical staff and public health workers as they respond to a crisis, but biosurveillance has traditionally relied on manual reporting by hospital administrators when they are least able: in the midst of a public health crisis. This article explores the use of health information exchange networks, which enable the secure flow of clinical data among otherwise unaffiliated providers across entire regions for the purposes of clinical care, as a tool for automated biosurveillance reporting. Additionally, this article uses a health information exchange to assess H1N1's effect on ED visit rates and discusses preparedness recommendations and lessons learned from the spring 2009 H1N1 experience across 11 geographically distinct EDs in New York City that participate in the health information exchange.