COVID-19 caught the world off guard. Syndromic surveillance systems are not new, but there are two common barriers to early detection of a new infectious disease outbreak. First, existing syndromic surveillance systems are operated in silos: Each hospital has its own monitoring, but does not share at the community, regional, national, or international level. Second, current systems rely on diagnoses, but ACT's S4 moves pathogen identification upstream through pattern recognition of symptoms.