Public health implications of emerging zoonoses.

Many new, emerging and re-emerging diseases of humans are caused by pathogens which originate from animals or products of animal origin. A wide variety of animal species, both domestic and wild, act as reservoirs for these pathogens, which may be viruses, bacteria or parasites. Given the extensive distribution of the animal species affected, the effective surveillance, prevention and control of zoonotic diseases pose a significant challenge. The authors describe the direct and indirect implications for public health of emerging zoonoses. Direct implications are defined as the consequences for human health in terms of morbidity and mortality. Indirect implications are defined as the effect of the influence of emerging zoonotic disease on two groups of people, namely: health professionals and the general public. Professional assessment of the importance of these diseases influences public health practices and structures, the identification of themes for research and allocation of resources at both national and international levels. The perception of the general public regarding the risks involved considerably influences policy-making in the health field. Extensive outbreaks of zoonotic disease are not uncommon, especially as the disease is often not recognised as zoonotic at the outset and may spread undetected for some time. However, in many instances, the direct impact on health of these new, emerging or re-emerging zoonoses has been small compared to that of other infectious diseases affecting humans. To illustrate the tremendous indirect impact of emerging zoonotic diseases on public health policy and structures and on public perception of health risks, the authors provide a number of examples, including that of the Ebola virus, avian influenza, monkeypox and bovine spongiform encephalopathy. Recent epidemics of these diseases have served as a reminder of the existence of infectious diseases and of the capacity of these diseases to occur unexpectedly in new locations and animal species. The need for greater international co-operation, better local, regional and global networks for communicable disease surveillance and pandemic planning is also illustrated by these examples. These diseases have contributed to the definition of new paradigms, especially relating to food safety policies and more generally to the protection of public health. Finally, the examples described emphasise the importance of intersectorial collaboration for disease containment, and of independence of sectorial interests and transparency when managing certain health risks.