the bubonic plague, spread by rats bitten bye infected fleas
Black Death or The Black Plague was spread by fleas that were on rats. The Industrial Revolution could be the cause of its rapid spreading, but the cause is actually disputed by many scientists and historians. Many think it spread just because of how contagious it was.
It spread from Asia to Europe and was found in all towns and cities. It killed around 40-50% of all people living at that time.
plague
It depends on which plague, but yes. Many viruses can be spread without touching a person due to the virus mutating and becoming airborne, or if the inflicted person touchs something that somebody else then touches.
epidemic
This was a very vague question, but I belive the word you are looking for is "Plague"
rats
The rats and fleas carried the black death ** Correction... Rat fleas carried the Bubonic Plague. There is still speculation as to whether the black death was actually bubonic plague as there are very many differences between the pandemics. One theory is that the black death was actually Ebola.
i won't pretend I'm an expert at this, but i believe the silk road spread over many miles and the plague spread through those in trade to those in villages and so on. therefore making it somewhat like a wildfire
Rats, lack of sanitation and lack of understanding of how sanitation keeps germs from spreading.
Around 23.8 million people died