Mc Keon, in nineteenth century studied the decline in the incidence of the infectious diseases like tuberculosis and he explained the co-relation between the declinein the incidence of infectious disease and told that the relation is better understood in terms of -

Thomas McKeown attributed the modern rise in the world population, AND DECLINE OF TB from the 1700's to the present to Broad economic and social changes (especially diet and nutrition- "Nutritional Determinism") rather than to targeted public health or medical interventions Ref: Internet