Abstract
After World War II, mankind believed that infectious diseases were on the way to being defeated. Unfortunately, they still are the second worldwide cause of death. Globalization changes promote the emergence of new infections and pandemics; international deliveries and travelling facilitate the dissemination of infectious agents; man-induced environmental changes create new opportunities for contacts between species, leading to infections in aberrant hosts, including man; global warming enables insects, a major vector of pathogens, to thrive in more countries. The main pandemics have been caused by viruses, such as HIV and novel subtypes of influenza viruses. In addition, prion proteins are a threat. The transmission of the Creutzfeld Jakob disease variant through blood transfusion and the recent discovery of prion protein in the spleen of a haemophilia patient are a matter of further concern. The end of the war against infectious diseases is not in sight. Mankind's battle with pathogens has lasted millennia and is destined to continue.