Free, at last!

Infectious diseases have moulded the development of the human species more than any other biological or abiological factor. They have influenced not only our biology, but also our history and political development; from the outcome of wars to the success of empires, and from the pace of technological advance to the structure of society itself. The introduction of smallpox to the Americas by European conquerors, for example, devastated the indigenous populations and destroyed mighty empires and advanced societies. In the 1400s, the Black Death killed between 30% and 60% of the European population, and continued to blight the continent intermittently until the eighteenth century with severe and lasting social, economic and political consequences. Similarly, the 1918–19 Spanish flu killed more people in less than one year than did the horrifying battlefields of the First World War. Even without causing major pandemics, persistent infectious diseases such as malaria, tuberculosis or measles have been imposing their burden on humanity with no less devastating effects. The use of hygienic practices and the development of vaccines and anti biotics have given modern doctors and public health experts the edge over infectious diseases. Yet, many experts have long debated how to rid humanity of the worst diseases once and for all. So far, this has been a matter of rather academic and political debate, although global disease eradication—the complete elimination of a pathogen— became a reality in 1980 when smallpox was officially consigned to history (see Sidebar A; Figs 1,2). Despite this significant success, and despite the enormous advances made by the biomedical sciences during the last century, many infectious and potentially eradicable diseases continue to take their toll on humankind, particularly on the poorest of the world’s people. However, some promising developments and successes during the past few years have rekindled the hope that further eradications can be achieved (Aylward & Birmingham, 2005). However, this does not necessarily imply that we will have to deal with fewer pathogens—we are ‘discovering’ new diseases much faster than we are eradicating old ones.