Diffusion

The spread of ideas from one culture to another is referred to in human geographical studies as cultural diffusion. Diffusion occurs through the movement of people, goods, or ideas. Diffusion has been broken up into to separate categories by geographers, expansion diffusion and relocation diffusion. In the case of expansion diffusion, an innovation or idea develops in a source area and remains strong there , while also spreading outward. For example, Islam spread from its hearth …

…aware of what causes the spread of AIDS yet it continues to spread. The problem is that if a woman’s husband dies, she then becomes his brother’s responsibility. In order for the husband’s spirit to go to heaven the brother must have intercourse with his deceased brother’s wife. If the dead man died of AIDS then his brother will also get it and spread it to his own wife and family