One Health is an emerging concept that aims to bring together human, animal, and environmental health. Achieving harmonized approaches for disease detection and prevention is difficult because traditional boundaries of medical and veterinary practice must be crossed. In the nineteenth and early twentieth centuries, this was not the case-then researchers like Louis Pasteur and Robert Koch and physicians like William Osler and Rudolph Virchow crossed the boundaries between animal and human health. More recently, Calvin Schwabe revived the concept of One Medicine. This was critical for the advancement of the field of epidemiology, especially as applied to zoonotic diseases. The future of One Health is at a crossroad with the need to more clearly define its boundaries and demonstrate its benefits. Interestingly, the greatest acceptance of One Health is seen in the developing world where it is having significant impacts on control of infectious diseases.
