A year and a half after revolt spread rapidly from Tunisia to Egypt and beyond, unrest is again unfolding throughout the Middle East.
It started earlier this week with an attack in Libya that killed the American ambassador as well as three of his staff members. By Thursday, protests sparked by an anti-Muslim video made in America had expanded to include at least six places around the Middle East, the New York Times reported.
Involved countries include Egypt, Morocco, Tunisia and Sudan, with the worst violence so far affecting Yemen. Afghanistan may be next.
Much like the series of events that unfolded in the region early last year, the recent uprisings demonstrate how common it is for revolts to trigger yet more revolt.
"Revolutions can sometimes be contagious," John McManus, a military historian at Missouri University of Science and Technology in Rolla, told Discovery News last year. "The take-home lesson from history is that you always have no idea how it's going to turn out, and that's kind of the scary part. You have no idea where the forces are going to go once they're unleashed."
Historical examples of contagious unrest include the American Revolution, the French revolt of 1848 that spread through Western Europe, the events leading up to the Civil War, and the fall of the Berlin Wall, which was just one part of a wave of uprisings against Communism in Poland, Romania, Hungary, Czechoslovakia and Bulgaria.
In modern times, discontent can spread more quickly than ever with the help of social networking tools like Facebook and Twitter.
Officials in the United States and the Middle East are scrambling to diffuse the current conflict before it spreads even further.
Photo: Egyptians clash with police overnight and into a third day of unrest
near the US Embassy in Cairo on Thursday. Credit Image: Corbis/Cliff Cheney