<Li> Changes in agriculture . The introduction of new crops attracts new crop pests and the microbes they carry to farming communities, exposing people to unfamiliar diseases . </Li> <Li> The destruction of rain forests . As countries make use of their rain forests, by building roads through forests and clearing areas for settlement or commercial ventures, people encounter insects and other animals harboring previously unknown microorganisms . </Li> <Li> Uncontrolled urbanization . The rapid growth of cities in many developing countries tends to concentrate large numbers of people into crowded areas with poor sanitation . These conditions foster transmission of contagious diseases . </Li> <Li> Modern transport . Ships and other cargo carriers often harbor unintended "passengers", that can spread diseases to faraway destinations . While with international jet - airplane travel, people infected with a disease can carry it to distant lands, or home to their families, before their first symptoms appear . </Li>

General infection is the least dangerous stage of an infection