Hard to know: Covid-19 was recently identified and named in 2019-2020. It had not been identified in the past as causing human disease although other strains of coronavirus have. Since there were no available tests to separate this strain from others found in nature it is not clear where it has been in nature or if it was actually new.
Answered 11/1/2021
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Coronavirus: The virus has been identified as far back as the 60's. The present strain was identified first in 2012. Its means of spread has not changed. Like many viruses, like Ebola for example or even the flu, exactly why the antigens on the surface change and cause more virulence is multifactorial.
Answered 3/5/2020
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