Quote:
Originally posted by codeoftherobot
It is not surprising that it started in China since their way of growing animals is very archaic and dangerous to health. Birds have been traced to be the cause of many flu and other respiratory diseases (beats me how but they just do. Just think about that bird you have in a cage ). The chickens are grown in close quarters to pig and cows so that the cows will unknowingly pick up the illness and when those animals are killed for meat or other products, the disease is passed onto humans.
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The reason deadly diseases usually come from animals is because from an evolutionary standpoint, killing your host is a very bad strategy. Their are millions of bacteria and viruses that are completely harmless to humans. Many have evolved to the point of coexisting with us. Diseases that kill the host to quickly must either mutate to a non-virulent strain or run their hosts into extinction, making it impossible to continue to spread. The diseases deadly to humans generally come from another organism that is similiar enough to humans for it to infect us (while being harmless to its normal host). The disease has not evolved to the point of coexisting or at least not heavily injuring us because we are not the normal host. Eventually the disease must either mutate into a harmless strain, eliminate all potential hosts, or kill its hosts before it can effeciently spread. In history "plagues" generally die out relatively quickly.