Changes in lifestyle, increased global movement of people and goods, an aging population, the spontaneous evolution of pathogens, as well as advances in medical technology and the emergence of antimicrobial resistance, are responsible for the constant emergence or resurgence of new pathogens and their spread among populations. The HIV pandemic and, more recently, the 2003 severe acute respiratory syndrome (SARS) outbreak clearly demonstrated that emerging risks constitute a global threat requiring a coordinated international approach supported by effective and responsive national systems. In addition to infectious diseases, environmental risks—whether of natural or anthropogenic origin—are also constantly evolving. The heatwave in the summer of 2003 demonstrated that environmental risks could lead to significant excess mortality over a short period, fully justifying the implementation of environmental early warning tools and daily monitoring of general indicators such as hospital admissions and mortality. Since September 11, 2001, the recognition of the risk of bioterrorist attacks has led to the integration of this new threat into the design of epidemiological warning systems. With a view to early detection, syndromic surveillance systems—which collect information when a patient visits an emergency department—have been developed. Tomorrow’s health emergencies will not necessarily be detected by alert systems that target known risks. Health alerts today rely not only on highly responsive monitoring of indicators targeting known health risks but also on proactive surveillance of phenomena of unknown nature that may pose a threat to public health, whether infectious or environmental. (Excerpt from the report).