It's a classic Hollywood storyline: A new disease pops up and spreads worldwide, much faster than science can come up with a cure. But this isn't just the stuff of action films. It's called a pandemic, and it's happened more than once in our history.
One that's still pretty well-known, despite the passage of several hundred years, is the Black Death. The plague originated in Asia, reaching Europe by the late 1340s where it killed a staggering number of people. Because the records back then weren't entirely thorough, no one is completely sure how many died, but estimates range from 25 million to 100 million [source: Filip]. Either way, it was nothing to sneeze at. In some cities, so few people survived that there was no one to bury the dead [source: Kennedy].
That kind of stuff only happened before modern medicine, right? Not exactly. There's another pandemic that started just four decades ago and continues to claim lives today: AIDS. This disease originated in Africa as early as 1920 but didn't spread worldwide until the 1980s [source: McCoy]. Since then, somewhere between 63 million and 89 million people have been infected with HIV, and 30 million to 42 million of those have died [source: UNAIDS]. That means, incredibly, that AIDS may have killed as many people — or even more — than the Black Death.
Yet, despite all that we know about such diseases, they still live on thanks to unsanitary conditions, cultural misunderstandings and a lack of education. Even the plague still rears its ugly head from time to time, particularly in developing countries in Africa and Asia. Which makes you wonder: Will we learn from these past pandemics, or are we setting ourselves up for another one?