This chapter examines the human health and economic consequences of emerging infections. It also presents the health and economic impact of two high profile emerging infection events – Severe Acute Respiratory Syndrome (SARS) and influenza. An outbreak caused by another breech in the animal/human species barrier occurred in the Guangdong Province of China in late 2002. The initial cases in the outbreak of SARS in China spread from human to human. Infected persons passed the infection to other family members and to health workers, and they in turn spread it to others in the community, causing an outbreak associated with severe illness and death. The International Health Regulations are a global framework agreement of all Member States of the World Health Organization, and are designed to limit the international spread of public health emergencies, including emerging infections, with minimal interruption to travel and trade.