Human Activities & the Emergence of Pathogens

The least movement is of importance to all nature. The entire ocean is affected by a pebble . –– Blaise Pascal Many infectious diseases were unknown to hunter and gatherer populations, in which the small size of groups, combined with their nomadic lifestyle, did not favor the establishment and transmission of human pathogens (Greger, 2007). The formation of larger human settlements that accompanied the development of agriculture, their proximity to species that were intentionally domesticated or unintentionally attracted by food, and the use of natural fertilizers that allowed microbial development are among the factors that shaped the emergence of infectious diseases. Measles originated from a related virus that infects sheep and goats, while smallpox and influenza were linked to the domestication of camels and waterfowl (Greger, 2007). As a result of human activities, certain pathogens, normally limited to other species, gained the ability to cross species barriers and subsequently became established in humans. A relevant example is illustrated by farming practices in southern China, where swine are often raised in proximity to ducks, geese, and humans. The overlapping habitats enable influenza virus …