Fighting the rise of emerging infectious diseases.

• Author: Brown, Corrie
• Position: Medicine & Health

EMERGING INFECTIOUS diseases (EIDs) are on the rise, occurring at an unprecedented rate in animal and human populations, and posing a major threat to the biological safety of our 21st century world. Mother Nature's potential threat may be, in the end, much greater than any destruction that could result from another world war, a nuclear bomb blast, or some heinous act of terrorism. In a worst-case scenario, the emergence of a new infectious disease with high transmissibility and mortality has the potential to devastate the human population before sufficient resources can be rallied effectively. We may have dodged a bullet with H1N1--the so--called swine flu--but have we learned our lesson as to what could have been?

The term "emerging disease" usually describes a known disease or closely related agent appearing in a new geographic area or occurring in a new species. It also could be a previously unknown disease agent detected for the first time.

Because 75% of emerging human diseases worldwide over the past two decades have originated from animal sources, there has been considerable consternation in the public health and veterinary communities. There is a critical need for a surveillance system that thoroughly integrates data on humans with that of wild and domestic animals, as veterinary pathologists often play a key role is the early detection of these EIDs.

"Zoonosis" is the term used to define an animal pathogen that moves into a human host. The highly pathogenic avian influenza virus (H5N1), or bird flu, is just one example of a zoonotic threat to human health and well-being. Others include severe acute respiratory syndrome (SARS), bovine spongiform encephalopathy (BSE) or "mad cow" disease, and the Ebola virus.

Given the ideal combination of circumstances, all have the potential to become epidemic or pandemic. "Epidemic" describes any widespread outbreak of an infectious disease, while the term "pandemic" typically is reserved for a global outbreak that affects a large proportion of the world's population.

The principal reasons that zoonotic diseases are so much more prevalent today are the increasing numbers of humans and the expanding globalization of trade. International commerce has tripled over the past 20 years, resulting in unprecedented levels of traffic in people, animals, and animal products. That, combined with unrelenting population growth, has created a synergy for microorganisms to move freely and quickly from their commonly inhabited domains into unexpected niches, often with lethal results.

Animal welfare, human health, and the environment all suffer as a result of these emerging diseases, but economic losses can be even more staggering. Owners and producers of animals and animal products experience direct losses from animal treatment costs, deaths, and the resulting decreased production, as well as from restrictions prohibiting the export or importation of infected...