Respuesta :
Black Death, which accounted for at least 1/3 of the European population, was known to have been caused by rats until 1894 when Japanese scientists finally traced it to a bacterium called Yersinia pestis. This bacteria is transmitted by fleas and the rats were the carriers.
Finally, it was determined that fleas on rats caused the black death, but that wasn’t until the global outbreak that happened more recently, in China, 1855 which was later declared as ended, in 1959, that we knew what actually happened. Scientists and specialists that studied the case determined that rats were one of the reasons for the spread of the disease. They achieved this by noticing that many rats were carrying symptoms of the plague that were similar to those that people were having. By realizing that many victims had flea bites, they eventually found out that the rat fleas were the ones carrying the disease.