Contrary to "lingering" zoonoses, public awareness of "emerging" zoonoses is very high. The WHO/FAO/OIE joint consultation on emerging zoonotic diseases held in Geneva, 3-5 May 2004, defined an emerging zoonosis as "a zoonosis that is newly recognized or newly evolved, or that has occurred previously but shows an increase in incidence or expansion in geographical, host or vector range". Emerging zoonotic diseases have potentially serious human health and economic impacts and their current upwards trends are likely to continue.
Examples are avian influenza, Bovine Spongiform Encephalitis (BSE) and the Nipah virus. Some of the "lingering" zoonoses are re-emerging in some regions, although they seem to attract less public awareness. Brucellosis, dog rabies and parasitic diseases such as cysticercosis/taeniasis and echinococcosis/hydatidosis for example.
Many factors lead to the emergence of zoonotic diseases. Environmental changes, human and animal demography, pathogen changes and changes in farming practice are a few of them. Social and cultural factors such as food habits and religious beliefs play a role too.