In March 2003, a global alert was issued regarding an outbreak of severe pneumonia that began in China and gradually spread to many countries within a few weeks. The viral origin (coronavirus) was quickly identified, with its severity evidenced by a case fatality rate of between 5 and 15%. This outbreak highlighted the need to develop a global health alert system in collaboration with the WHO. The emergence of new infectious agents, particularly viruses transmitted from animals to humans, constitutes a risk that is increasingly well identified, and whose rapid international spread is facilitated by the growth of human migration and air travel. In two months, 8,000 cases were identified in 31 countries, resulting in more than 600 deaths. The active mobilization of the healthcare system and professionals, along with the implementation of an early policy for detection, isolation, and management of cases, is the essential element in controlling the epidemic risk. Informing the public, in the context of a global epidemic, remains difficult, and security-related abuses pose a significant risk to healthcare professionals and exposed populations.