When it comes to biological factors that tear through entire species, humans can't take all the credit.
Remember how the West African Ebola outbreak of April 2014 stirred up fears of how far and fast a virulent disease could spread — and of how ill-prepared to deal with it we might be? You should, because days after the World Health Organization pronounced the region Ebola-free in 2016, another case popped up [source: Fox].
History has shown that a pandemic now and then can be a good thing, at least for the survivors. Apart from their traumatic emotional effects, pandemics can create better prospects for poor laborers and aid in ecological recovery, as long as they don't kill too large a fraction of the population. But while in progress, they can profoundly alter how societies function, taxing infrastructures well beyond their tolerances and forcing people to spend their off-work hours nursing family members.
A disease that kills 80 to 90 percent of all people on Earth could tip this balance toward an unrecoverable social and technological crash. The more we travel, alter our landscapes and closely mingle with all types of animals, the more we increase our risks [source: Vince].
So how likely is either of these events? It's hard to say. We've averaged a pandemic roughly every 10 to 50 years over the past few centuries, with the most recent being the global H1N1 flu pandemic in 2009 and 2010 [source: Vince]. That means another pandemic could happen during your lifetime.