ABSTRACT
Disease has long been the greatest threat of all to humanity and, despite the advances of medical science, looks set to continue to be for the foreseeable future. As with famines and hunger, however, major epidemics and pandemics of diseases represent only dramatic periodic escalations of an underlying and persistent threat. Immigrants can, of course, be ‘vetted’ for alien diseases by state authorities before admission into the country, but this is neither feasible nor politically acceptable for tourists and other visitors entering or, particularly, for citizens returning from abroad. The globalization of the human strategy of antibiotic use and chemical pest control has had the side effect of globalizing resistance. Both pathogens and the pests by which they are transmitted have increasingly developed immunities to the pesticides and antibiotic drugs used against them. Human-driven changes to the environment other than urbanization can also upset the equilibrium in a given ecosystem and cause a resurgence of certain diseases.
