Dr. Morse reminded his listeners of the changing relationships between humans and the environment.
Infectious diseases are the leading cause of death worldwide.
Viral emerging diseases undergo a two-stage process. In the first, virus meets human and there are many factors responsible for its appearance and dissemination. The viruses come from nature and, in the process, we are sampling nature's diversity. In the second stage the virus becomes both established and disseminated. Human intervention is a factor in the emergence of viruses, and he gave as an example the effect of agricultural practices in the development of new strains of the influenza virus, which seem to travel from ducks to pigs to humans.