RESUMO
As with other infectious diseases over thhe world, leprosy tends to be more severe and rapidly progressive in the regions of lesser climatic stimulation. It is almost universally true that those areas of the earth with a stimulation index of less than 3.0 are cursed with leprosy as a major public health problem. With an index above 6.0 the disease becomes distinctly more mild and less prevalent, while above 12.0 it continues to exist only by important of cases. Where the stimulation rises to 18.0 or above, there seems to occur a spontaneous cessation of the disease as a public health problem. Leprosy, imported from the tropics into cooler portions of the earth, persists only in those regions of benumbing cold where the real index of climatic stimulation falls to subtropical levels. Scandinavia and the maritime provinces of Canada, with their long cold winters, exemplify this depressing effect of prolonged cold on body vitality. The last wave of leprosy in Norway coincided to a remarkable degree with a world-wide period of subnormal temperatures and increased storminess. On the other hand there is considerable evidence that, when the disease spread with such virulence over Europe in the Middle Ages, the earth was under the influence of a major heat wave that sapped the vigor and vitality of population masses in temperate zones...