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There have been several alternate explanations of the pandemic called the Black Death, a couple of them viral: measles and smallpox. The difficulty is that the symptoms described don't appear to match the known symptoms of either of these, nor do they match those of a hemorrhagic fever such as Marburg or Ebola.

There were three forms of the disease: bubonic, wherein the major symptom was a highly swollen lymph node, septicemic, a blood infection, and pneumonic, where the disease was contracted from inhalation of infected droplets. All of these can be caused by Yersinia pestis, and that isn't true for the alternates. So either we're dealing with more than one simultaneous plague, perhaps as many as three, or we're dealing with one disease organism that causes all three. For the latter, Y. pestis seems the best, but not the only, fit.

Historical epidemiology has another couple of mystery plagues: the Plague of Athens (429 BC) that has never been convincingly identified and that has been theorized to be an Ebola sort of virus as well as Yersinia pestis, typhus, smallpox, measles, etc, etc; and the Plague of Justinian (AD 541) that most authorities think to be a strain of Y. pestis that became extinct afterwards, but in fact could have been nearly any of the others. These plagues were world-changers: the first determined the eventual outcome of the Peloponnesian War and hence much of the subsequent history of the West, and the second, one of the factors that so depopulated north Africa and Asia Minor that the onslaught of Islam in the next century became possible.

Fun stuff to read about and consider in the comfort of one's study, not so much fun to live through. I don't think we're about to do any such thing, but then there were people who said that in the 14th and 6th centuries AD, and 5th century BC that probably said the same.