With the arrival of anibiotics and modern vaccines, as well as improved sanitation and hygiene, many diseases that formerly posed an urgent threat to public health were brought under control or largely eliminated. As a result, by the mid-20th century some scientists thought that medical science had conquered infectious diseases.
Despite these public health advances, new microbes emerge and old microbes re-emerge just as they have throughout history. Several pressures contribute to the emergence of diseases, such as
Practices such as the misuse of antibiotic medicines also contribute to disease emergence.
In addition, unsanitary conditions in animal agriculture and increasing commerce in exotic animals (for food and as pets) have contributed to the rise in opportunity for animal microbes to jump from animals to humans. From time to time, with the right combination of selective pressures, a formerly harmless microbe found in humans or animals can evolve into a pathogen that can cause a major outbreak of human disease. These pressures are shaping the evolution of microbes and bringing people into closer and more frequent contact with pathogens.
Last Updated November 02, 2010