Public health has been defined as "the science and art of preventing disease, prolonging life and promoting health through the organized efforts and informed choices of society, organizations, public and private, communities and individuals"(Winslow 1920) or as "the art of applying science in the context of politics so as to reduce inequalities in health while ensuring the best health for the greatest number"(WHO1998). As the challenges of public health have evolved, from sanitary surveillance and infectious diseases in the past, to chronic diseases, lifestyle factors,socioeconomic conditions, occupational and environmental health determinants,health reforms and others, so have the methods of assessment advanced by research technologies development. The new health threats and epidemics, such as AIDS, SARS (Severe Acute Respiratory Syndrome), influenza H5N1, or emergencies like natural disasters or bioterrorism, effects of globalization and migration present new tasks to public health governance requiring new working methods.
