One of the most important health issues faced by the world today is the threat of a global disease outbreak called a pandemic. A pandemic is an epidemic infectious disease that spreads rapidly to several areas of the world, affecting a very high number of people. In accordance with the WHO (World Health Organization) definition, a pandemic is declared if a new disease spreads worldwide involving at least two continents. When it is used in reference to contagious diseases or conditions, the risk is that the entire world population is likely to be exposed to the pathogenic agent and develop the disease. These diseases are caused by newly detected or re-emerging biological agents. Analysing the history of outbreaks caused by these agents and trends in epidemiological data can help to better identify the related risks for the whole population, and save lives.