When revolution struck the Middle East during the Arab Spring in late 2010, it seemed clear that the seeds of discontent were spreading from one country to another, linked by common frustrations and similar goals.
Now, simultaneous uprisings in Ukraine, Venezuela and Thailand are raising questions about whether revolutions can be contagious, even when countries are separated by continents and oceans.
For now, experts said, current revolts in disparate countries seem mostly unrelated, though they do share similar tactics. Still, it wouldn't be unprecedented for revolutions to spark unrest from afar.
Ever since literacy became commonplace and international lines of communication opened up hundreds of years ago, people have been sharing ideas and gaining inspiration from the struggles of others.
"Revolutions can absolutely be contagious," said Colin Beck, a sociologist at Pomona College in Claremont, Calif. "In the modern world, most revolutions happen as part of revolutionary waves. It's been an increasing trend in the last 200 to 300 years."
There are two prerequisites for a revolt to spread beyond its borders, Beck said. First, there needs to be success. "No one is going to imitate a failed revolution," he said.
Potential dissenters also need to have a sense that an ongoing or recent revolt is relevant to what's happening where they live. When societies are similar, activists can more easily become emboldened and confident that they might succeed, too.
There are many historical examples of uprisings catching on in non-adjacent regions.
The French Revolution, for instance, began just a few years after the American Revolution ended in 1783. By that point, France's rising class of non-aristocratic, anti-British property owners was already fed up with the excesses of the monarchy, said John McManus, a military historian at Missouri University of Science and Technology in Rolla.