Emerging infectious disease (EID) are diseases that have not appear in humans before OR have occurred before but only affected small numbers of population in isolated area OR have happened throughout human history but have only recently been recognized that infectious agent as the underlying cause.

Public health is a 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

CEA Winslow

Public health is about searching the effective way to secure health and prevent disease in the population. The strategies to dealt with diseases evolved through trial and error, scientific knowledge, also related to societal condition, religion, culture, beliefs. The evolution of public health thinking is a dynamic process, although there is much new perspective and arguments in public health today, many of the currents debate are echoes of the past.