Where viruses or diseases that you get from other people come from? Like how does the first person end up with it?

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Where viruses or diseases that you get from other people come from? Like how does the first person end up with it?

In: Biology

Viruses and other infectious diseases have evolved alongside life from the beginning. The first human to catch a disease was the first human, whatever descended from an arbitrarily defined proto-human.

Viruses also evolve and can sometimes jump between species. HIV seems to have evolved from SIV in monkees, and new kinds of influenza can apparently start in pigs and jump to humans who live in close contact.

P.S. From what I’ve read, interspecies infection can start slowly with little ability to infect, and gradually adapt to the new species.

Viruses, bacteria and other microbes typically coexist with their hosts without causing huge problems, but every now and then one will mutate and become more virulent. The most susceptible will get sick and often die while the resistant pass that trait along to their offspring who over time become increasingly resistant until the disease is no longer particularly dangerous. Then it mutates again and the whole process starts over.