Likely very little. By the 17th century, when there were severe recurrent outbreaks of plague in Europe and Britain, some people were certainly reading Thucydides, who recorded the plague of Athens. But literacy was much rarer prior to the 14th century plague, including among physicians. Indeed, if we look at the way that 14th century people interpreted the plague, it doesn't seem like they read Greek or Roman accounts of similar epidemics.