Like all living creatures, microbes have evolved over time in human, animal, insect and plant populations that were separated by oceans and mountain ranges. Over the past 150 years our ever-changing and rapidly growing trade and travel dynamics have resulted in a global mixing bowl for all forms of life. In particular, this is true of human and animal disease-causing microbes. We face unprecedented challenges with controlling and preventing infectious diseases in this new worldwide reality. Microbes do not respect borders. This presentation will address this unique and defining public health challenge.