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Sorry for my lack of understanding, Why now, when people been eating bats for centuries? If bats are simply a vector, where does that virus come from?

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    $\begingroup$ Please see the meta discussion and contribute. I thoroughly disagree that biology.SE doesn't have the expertise to answer questions about biological concepts and disease mechanisms as they relate to virology. They are, in fact, explicitly on topic. This question's problems are related to the lack of prior research. Address that issue and I will vote to re-open. $\endgroup$
    – De Novo
    Feb 5 '20 at 4:42
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Bats are reservoirs of many important human pathogens, some are emerging infections (e.g., 2019-NCoV, the coronavirus in the news recently), and some are not (e.g., rabies).

Contact between humans and bats is certainly not a new phenomena, but there is more required for an emerging infection than a reservoir and a new host. There must be some bridge that allows a virus to cross a previously effective species barrier. For SARS, there was an intervening amplifying host, the palm civet. We've now had long enough to study the molecular biology, so this is now quite well described:

Once SARS-CoV had jumped from bats to civets, it underwent further mutations in civets. The first K479N mutation allowed SARS-CoV to jump from civets to humans and the second S487T mutation allowed SARS-CoV to transmit from human to human, leading to the severe SARS outbreak in 2002–2003.

It may be useful to understand that, as they are RNA viruses, coronaviridae have a high error rate, increasing the rate of mutation. Additionally, making a species jump may allow for novel recombination.

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  • $\begingroup$ I think you could expand a bit on the lack of stability in viral populations. $\endgroup$
    – Bryan Krause
    Feb 1 '20 at 4:33
  • $\begingroup$ @BryanKrause done. Feel free to expand further if you'd like. $\endgroup$
    – De Novo
    Feb 5 '20 at 4:20
  • $\begingroup$ The four endemic human coronaviruses are all bat-origin coronaviruses that have jumped into humans in the past 100 years, so the premise of the question is wrong. $\endgroup$
    – iayork
    Feb 5 '20 at 14:27
  • $\begingroup$ @iayork that's fascinating. For some reason I was remembering bovine coronavirus, rather than bat as a source for human coronaviruses. $\endgroup$
    – De Novo
    Feb 5 '20 at 19:07
  • $\begingroup$ A more recent study suggests that two of them may have passed through livestock first (ncbi.nlm.nih.gov/m/pubmed/29551135) and may or may not have started in rodents $\endgroup$
    – iayork
    Feb 5 '20 at 20:02

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