Data is gathered from Maryland's Emergency Departments using the Electronic Surveillance System for the Early Notification of Community-based Epidemics (ESSENCE)​. Additional data is compiled from the Centers for Disease Control and Prevention's (CDC's) Health Alert Network, the Maryland Department of Health Prevention and Health Promotion Administration, the Maryland Institute for Emergency Medical Services Systems (MIEMSS), the World Health Organization, the National Electronic Disease Surveillance System, and the Program for Monitoring Emerging Diseases (ProMED).​