Different zoonoses whose etiologic agents were previously unknown have been identified in recent years as a result of new diagnostic techniques in molecular biology and improved epidemiological surveillance systems. Several factors have facilitated the emergence of new diseases and the reemergence of already known diseases, which were thought to be under control.

They include the following:

(1) environmental changes, such as deforestation and droughts, which allow etiologic agents and their vectors to thrive, (2) industrial food production for widespread consumption, which allows disease agents to spread quickly, (3) certain risky human habits, especially among immuno-compromised persons, such as having exotic pets at home, and (4) the adaptation of etiologic agents to new environmental conditions through the development of drug resistance. Other factors, such as the disruption of established health systems during the process of privatization, have also contributed to the situation. In most cases, bacterial zoonoses can be prevented through good personal and domestic hygiene and common sense. This report is not an exhaustive presentation of all emerging and reemerging bacterial zoonoses. Rather, it aims to illustrate, through numerous examples, the various factors that have contributed to the epidemiological changes that have taken place since the latter part of the twentieth century