Turns out the Black Death really was the granddaddy of them all. Scientists have mapped the genome of the bacteria that caused the bubonic plague and traced it to all modern incarnations of the disease.
Scientists recently pinpointed Yersinia pestis as the bacteria that killed 50 million people in the 14th century. After pulling the bacteria off rotting bones in an East London "plague pit" scientists decoded its DNA and found that it's genetically very similar to the DNA of the bacteria which cause disease outbreaks today.
OK, so that sounds insanely terrifying, but it's not as bad as you think. Scientists are actually DYING to know why the heck the plague doesn't kill as many people as it used to given that the bacteria has evolved so little over the last 600 years. Evidence suggests that human adaptation might be protecting us from further outbreaks, but the virulence of the disease could be affected by small genetic changes in the bacteria as well. By studying these changes over time, scientists hope to learn why the ancient bacteria was so deadly—and hopefully a thing or two about modern-day bacterial killers as well.