Unpurified drinking water, improper use of antibiotics, local warfare, massive refugee migration have contributed to changing social and environmental conditions around the world. These have fostered the spread of new and potentially devastating viruses and diseases : HIV, Lassa, Ebola, and others. The author takes the reader on a fifty year journey through the world's battles with microbes and examines the worldwide conditions that have culminated in recurrent outbreaks of newly discovered diseases, epidemics of diseases migrating to new areas, and mutated old diseases that are no longer curable.