Impact of zoonoses on human health.

Meslin, F X

By reviewing the most significant zoonotic disease outbreaks that have occurred mostly during the past ten years, the author provides a clear idea of how varied these diseases can be in regard to their aetiological agent, size and direct impact on public health. Most examples involve emerging zoonotic diseases caused by viruses and prions and transmitted to humans by a bite, close contact with affected live animals or carcasses, or through the consumption of their tissues. These outbreaks vary from very small and localised clusters of individual cases to millions of deaths, as reported during the past influenza pandemics. The author also shows that even for the larger outbreaks, the direct impact on public health measured by the morbidity and mortality of zoonoses is largely inferior to that of major communicable diseases that affect only humans, particularly human tuberculosis, malaria, HIV/AIDS. However, it is very difficult to predict the outcome on public health of these emerging zoonotic diseases since transmission patterns are not always sufficiently understood to assess this impact accurately. In addition, new modes of agent transmission may compound the initial impact on public health. Finally, the author indicates additional reasons that explain why these diseases are important by placing special emphasis on the financial losses recorded in both human and animal health and also the societal non-monetary losses these diseases can incur. Lessons learnt following major crises generated by the emergence of zoonotic diseases, such as bovine spongiform encephalopathy, severe acute respiratory syndrome and avian influenza, are provided.