Time, travel and infection

The collapse of geographical space over the last 200 years has had profound effects on the circulation of human populations and on the transfer of infectious diseases. Three examples are used to illustrate the process: (a) the impact of the switch from sail to steamships in importing measles into Fiji over a 40-year period; (b) changes in measles epidemic behaviour in Iceland over a 150-year period; and (c) changes in the spread of cholera within the United States over a 35-year period. In each case, the link between time, travel and disease has been an intimate one. Over the last 200 years, the earth’s human population has grown seven-fold from less than a billion to over six billion. Half of that increase has come in the last 40 years. Striking as this is, still more impressive has been the growth in the spatial mobility or volatility of the expanding population as transport barriers have been reduced. In western countries this has increased mobility 1000-fold with half the rise coming since 1960. If we combine the two increases of populatio