Eradicating sources or removing results.

With few exceptions, the prevalence of disease has never been reduced by improved treatment. Success has followed identifying and eliminating, or reducing, causative factors. This has been true of infective disease in the West and of the great tropical epidemics. Yet vastly greater endeavour and expenditure are devoted to the treatment of non-infective diseases than to efforts to identify and tackle their causes. This in spite of the fact that they are increasingly recognized as characteristic of modern western culture.