How are historians able to identify the specific pathogens that were the causes of pandemics and plagues that occurred in the distant past with any certainty? Are there any ancient diseases that remain unidentified or a mystery?

by JustinJSrisuk
voyeur324

/u/anthropology_nerd has talked about this numerous times, recently in response to I've been taught that when Europeans found the new world, they brought with them many diseases that wiped out the native American population. but- wouldn't this work both ways? wouldnt the colonists encounter new diseases in America that they had no immunity to?

See also Why were Native American populations in South America so much larger than North?