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The black plague is one of the deadliest diseases humans have ever faced; it killed as many as 50 million people - including about a third of the population of Europe - in the 14th century alone, in an outbreak known as the Black Death. In modern days, though, you hardly ever hear about people getting the plague, which might make you think we've wiped it out. But the black plague is still around and still infecting people - and we aren't even trying to eradicate it. Hi, I'm Kate and this is MinuteEarth. The black plague - technically known as the "bubonic" plague - is caused by a bacteria called Yersinia pestis.
This germ has a life cycle that normally goes back and forth between fleas and rodents. But occasionally it jumps into humans. And in humans, the disease is nasty; it fills a person's lymph nodes with pus - sometimes to the point of bursting - and eventually shuts down their organs. In times and places where lots of humans lived alongside lots of rats and fleas - like areas of poverty in big, crowded cities - the plague could spread far and fast; this has happened again and again throughout history and around the world. So you'd think we'd be doing everything in our power to kill it off once and for all - but we aren't.
It is true that, as we've distanced ourselves from rats and fleas and learned how to interrupt the transmission of infectious diseases, we've stopped the plague from turning into a modern pandemic. But Yersinia pestis hasn't completely disappeared; now, it's just hiding out in populations of wild rodents. Most of these critters don't get super-sick from the plague, so the disease just lurks in these so-called "reservoirs" - and every once in a while, it infects an unlucky human. These days, only about a thousand people worldwide get the plague each year - that's about half as many as get struck by lightning, which is pretty much the benchmark for rare-ness.
Plus, a course of modern antibiotics can generally treat the infection. So one reason we're not trying to eliminate the plague is that it isn't a big medical priority. Another big reason is that completely eradicating this disease is simply too much trouble. In fact, we've tried - and failed! About a hundred years ago, the Soviet Union funneled poison into burrows all across the country in an effort to destroy rodents that might be carrying the disease, and sprayed massive amounts of insecticides to kill infected fleas. But they couldn't kill off every single potential plague-infected critter,
and the rodents and fleas kept bouncing back, still carrying the plague. Around the world, there are dozens of different rodent species that serve as reservoirs for Yersinia pestis. Killing them all off would be incredibly difficult, if not impossible, not to mention a complete ecological nightmare. That, combined with the fact that the plague isn't much of a major medical issue anymore, is why there are no large-scale modern efforts to eradicate the plague. Ultimately, we haven't gotten rid of the plague because these days, it doesn't plague us enough to bother.
