We took a survey in our class, the question being, "Which do you think caused the Bubonic plague?" Most people chose mosquitoes, a common carrier of the disease, Malaria. Mosquitoes have also carried many other deadly diseases. Brackish water, if you didn't know, is fresh water mixed with salt water.  It makes you even thirstier, and it dries up your immune system.  This is what wiped out many of the colonists in 1607. However, you have learned from our website that the correct answer is fleas. Well, the most correct answer on the graph. The real cause is something a little more specific. Search our website to try and find the more specific answer.