Abstract
The New York City Department of Health has been developing two public health surveillance systems for chronic diseases. The first is the NYC Macroscope, which is built on a distributed query network of 740 New York City ambulatory practices all using proprietary software from one EHR vendor. The second model, Query Health, still in its initial phase, accesses data collected by a Health Information Exchange. This study compares these two models for potential disease surveillance and public health application.