At the beginning of the 21st century, the major cause of many human diseases and public health emergencies that have been considered "new and emerging" have resulted from pathogens originating from animals and their products. Newly emerged zoonoses such as bovine spongiform encephalopathy (BSE), other foodborne diseases and a number of viral infectious agents (Nipah, Ebola, avian H5N1 influenza virus, Monkeypox virus) have had serious direct and indirect impact on public health. A wide variety of animal species, both domesticated and wild, have acted as reservoirs for these pathogens which have included viruses, bacteria and parasites. Considering the wide span of animal species involved and the usually complex natural history of the pathogens concerned, effective surveillance, prevention and control of zoonotic diseases have posed a real challenge to public health.
More such occurrences can be expected in the future as the alteration of our environment continues. In most situations, proposed hypotheses for the emergence of a new agent refer to the complex interaction of numerous factors such as relative size of animal species populations, increasing human populations and settlements, change in technology, and maybe the influence of global climatic changes.
WHO's task in this increasingly important area of public health is to strengthen the capacity of Member states and the international community to identify, prevent and respond to such dangers, and to minimize their impact on public health by working with our partners within a global framework.