PARIS (AFP) - The wave of terror attacks afflicting Europe is showing signs of "contagion", experts warn, at a time when the continent is already in the throes of an existential crisis.
In less than two weeks, Islamic State in Iraq and Syria (ISIS) militants claimed four bloody assaults in France and Germany that killed nearly 90 people, wounded hundreds and left the continent on edge.
Experts say each attack can inspire another, with militants egged on further by the media spotlight the atrocities attract.
"Terrorism tends to be contagious," international security consultant Benoit Gomis told AFP, citing previous research that has shown attacks since the 1970s have occurred in "clusters or bursts".
"The last few months confirm this decades-long trend," he added.
The attacks come as Europe grapples with ever-mounting tensions and uncertainty.
The Greek debt standoff, the migrant crisis that saw more than a million people stream into Europe in 2015, and most recently Britain's shock vote to quit the European Union have come on top of an enduring economic malaise.
"It's a tipping point. Where do we go from here?" asked radicalisation expert Tahir Abbas of the London-based Royal United Services Institute (RUSI) think-tank.
"My fear is that it could get a lot worse because of the underlying conditions, and the economy is weak."
Over 12 days starting July 14, a driver ploughed a 19-tonne truck into the crowd leaving a fireworks display in Nice, a man set upon train passengers with an axe in Bavaria, another blew himself up outside a music festival, also in Bavaria, and two militants slashed a priest's throat in northern France.
During the same period nine people were shot dead at a Munich mall by an 18-year-old "obsessed" with mass killers like Norwegian right-wing fanatic Anders Behring Breivik, authorities said.
Emily Winterbotham, a senior researcher at RUSI, said the recent surge in violence "could be because people are emboldened by seeing others' acts, seeing they can cause so much damage by driving a lorry down a busy road.
"They are emboldened by seeing other people 'succeed'."
Both the Munich mall shooter and the driver of the truck that rammed the crowd in Nice, killing 84, had done research on previous mass killings.
The wall-to-wall news coverage that follows major attacks can also encourage would-be militants, said Michael Jetter, a University of Western Australia professor who has studied the effect of media coverage on terrorist activity.
"There is the potential that people disenfranchised from society, or who are very unhappy, young males that are not integrated into societies, may be drawn to such coverage and think 'Hey, if I do this, I will get my two or three days of fame'," he added.
"And it's what we should try to avoid."
On Wednesday, several major French media outlets decided they would no longer use pictures of the perpetrators of attacks, including one that said it would stop naming them.
Researchers have noted a similar interplay between media attention and so-called suicide clusters, which occur when several people take their own lives in a short period often in a defined geographical area.
ISIS' violent ideology can provide would-be attackers the justification and framework they are looking for to trigger massacres, experts say.
And while ISIS has lost ground in recent months in Syria and Iraq, its propaganda machine - which uses slick videos and publications to inspire attacks - is as strong as ever.
"The violent mindset... of this group (ISIS) is spreading like a contagion, by winning the hearts and minds of young people who perhaps have never even met the leaders of ISIS or Al-Qaeda and their branches," said Sara Silvestri, a Cambridge University expert on Islam in Europe.
And as militant violence breeds copycat attacks, it also fans fears of reprisals that threaten to further divide society - exactly as ISIS wants, experts say.
France, home to Europe's largest Muslim community, saw anti-Muslim acts of hate triple in 2015, with spikes coming after last year's two major militant attacks in Paris in January and November.
"Taking it one step further, let's hope that we don't see a retaliation" for the priest's murder, said RUSI's Winterbotham.