[Cholera: epidemiology and transmission. Experience from several humanitarian interventions in Africa, Indian Ocean and Central America].

With more than 50 countries affected and 200,000 notified cases per year (which is a gross underestimation), cholera, after having almost disappeared 50 years ago, has again become the calamity it was in the 19th century. To understand how this plague could have suddenly reappeared and spread all over the world and then taken root in the world's poorest countries, we give a brief outline here of the epidemiology of cholera, divided into three parts. The first part examines the origin and spread of the cholera pandemics, and particularly that of the seventh pandemic which, more than forty years after it began, is still, raging, in successive epidemic waves. The second part describes the modes of transmission of the cholera vibrio as they are seen in the field, examining the case of the cholera epidemic in the Comoro Islands in 1998. The third part shows the links between cholera and humanitarian disasters, through the use of concrete examples (refugee settlements, cyclones and volcanic eruptions). In conclusion, all the arguments presented here highlight not only the role of water and the lack of hygiene, but also the role of technical progress, especially in international transports, in the spread of the present pandemic.