Theory of the eradication of malaria.

The natural disappearance of malaria from certain areas-a phenomenon which has for many years been observed in various parts of the world-is discussed in relation to the recent deliberate elimination of the disease from large tracts of land. The process of elimination, the detection of residual foci, and the ways in which the disease may be reintroduced into a country are outlined briefly, and the course of events in epidemics which arise from small origins is described in detail. The factors affecting the basic reproduction rate in such epidemics-mean duration of infectivity of a primary malaria case, density of mosquitos in relation to man, and longevity and degree of anthropophilism of the vector concerned-are analysed, and a simplified method of expressing this rate mathematically is given in an annex.