Influenza and the work of the World Health Organization.

Before World War I, influenza was not considered a particularly serious problem. The great pandemic of 1918-1919 changed all that, and the possibility that such a catastrophe could occur again has conditioned all subsequent developments. In epidemiological terms, the hallmark of an influenza is the excess mortality that it causes combined with an enormous burden of ill-health that saps the energy of individuals, families and communities throughout the whole world. In order to engage in influenza prevention and control, the global influenza surveillance network was set up by World Health Organization (WHO) in 1948 as a worldwide alert system for the identification of new influenza viruses, gathering information from 110 participating laboratories in 82 countries and four WHO Collaborating Centers for Influenza reference and research: Centers for Disease Control and Prevention, Atlanta (USA), National Institute for Medical Research, London (UK), WHO Collaborating Centre for Influenza Reference and Research, Melbourne (Australia) and the National Institute for Infectious Diseases, Tokyo (Japan). This network helps WHO to monitor influenza activity all over the world and provides the organization with the viral isolates and information it requires to decide which new virus strains will be used to produce influenza vaccines during the following season. Each year, information about the isolates over the previous 12 months is analyzed and used to determine the composition of the influenza vaccine to be administered during the coming influenza season both for the northern and southern hemisphere. If necessary, the recommendations for the southern hemisphere differ from the ones formulated for the northern hemisphere vaccine. The information supplied by this network enables the organization to regularly update its World Wide Web (WWW) site (FluNet), which reports on the situation of diseases. This network will also enable the WHO to detect a new influenza pandemic as early as possible.

Hepatitis C.

Hepatitis C has been identified as the most common cause of post-transfusion hepatitis worldwide, accounting for approximately 90% of this disease in Japan, the United States and Western Europe. Hepatitis C is a major global public health problem. New infections continue to occur, and the source of infection includes transfusion of blood or blood products from unscreened donors; transfusion of blood products that have not undergone viral inactivation; parenteral exposure to blood through use of contaminated and inadequately sterilized instruments and needles used in medical, dental and 'traditional' medicine; procedures such as hemodialysis; high risk sexual practices; household or sexual contacts of hepatitis C virus (HCV)-infected persons; and infants of HCV-infected mothers. In many countries, the relative contribution of the various sources of infection has not been defined with population-based epidemiological studies. Such studies are necessary to enable countries to prioritize their preventive measures and to make the most appropriate use of available resources. Given the substantial morbidity and mortality attributable to HCV-related chronic liver disease, each country, irrespective of economic status, should develop a plan of HCV-related public health activities for the prevention of new HCV infections and the treatment of established chronic infections.