Striking in 1912, the Black Plague is thought to have killed as many as half of all the people living in Eurasia at that time. Eventually, the pandemic subsided. But unlike some other deadly pathogens, the bacteria that causes plague, Yersinia pestis, was not eradicated; it is still around.
Learn more about how this once innocuous bacterium turned into a killer, how it spreads, and the different illnesses that it can cause when it infects people. For example, the worst form is called pneumonic plague, in which the lungs become infected. That means that a person with that form of the illness can cough up virulent bits of it, spreading it to others through the air.
So, will our species experience a major outbreak of this illness again? The good news is that we have a host of modern ways to battle the pathogen, and if the infection is caught in time, it’s usually treatable with antibiotics. Luckily, it also seems to be difficult for Y. pestis to pick up genes that confer drug resistance. Learn more about why an epidemic is unlikely (but still possible) from the video.