EMSA is the front door of PHAST. It receives electronic messages, like lab and case reports, from healthcare providers. These messages come in a variety of formats and structures. EMSA standardizes all of these messages and automatically processes them according to a series of rules. These rules are customized to meet the needs of each Public Health Authority that uses it. Once the message is standardized and automated, the information from the message is sent to the Public Health Authority's disease surveillance system.