New emerging infectious diseases include "severe acute respiratory distress syndrome" (SARS) and avian influenza A H5N1. First cases of SARS, induced by a new strain of coronavirus, were described in China in 2002 and by May 2003 8360 cases and 764 deaths were reported by the World Health Organization. The disease can be transmitted from person to person and at the onset is characterized by nonspecific symptoms such as a fever of > 38 degrees C, dry cough, myalgia, and dyspnea. Adults can develop severe hypoxemia requiring intubation, whereas the course of the disease is generally benign in children. Avian influenza A H5N1 is another emerging infectious disease transmitted from avian species to humans, without clear evidence of transmission from human to human. The widespread outbreaks of H5N1 avian influenza in 2003-2004 have caused major problems for the poultry industry in many Asian countries. On January 2004 the disease crossed over to humans, for the first time in Vietnam, causing 74 deaths to date (mortality rate of 50%) in southeastern countries. Unlike SARS, the avian flu occurs in rural areas, where people live in intimate contact with birds, and many of the victims are children < 5 years of age. As for SARS, the World Health Organization has adopted a global action plan to control avian influenza among chickens and ducks and at the same time to limit the threat of a human flu pandemic.