(Bloomberg) -- Japan’s famed conveyor-belt sushi restaurants are scrambling to tackle a craze for making viral videos in which customers commit unhygienic acts.

The phenomenon, dubbed “Sushi Terrorism,” gained steam earlier this week after a teenager posted a video to social media filmed in Japan’s largest conveyor belt sushi chain. In it, he licked communal items including a soy sauce bottle and a bowl, and touched sushi as it rolled past with fingers he had put in his mouth.

The video, taken in Gifu city quickly went viral on platforms including Twitter, sparking a wave of copycat incidents and sending shares in the restaurant’s parent company down 4.8% on Tuesday.

The video pranks come at a particularly sensitive time for Japan, which is currently suffering its deadliest Covid outbreak since the pandemic began, and as restaurants struggle to survive amid surging inflation.

Food & Life Cos., which owns Akindo Sushiro, the outlet where the incident occurred, said in a statement this week it had filed a police report and received an apology from the perpetrator.

A spokesperson for the firm told Bloomberg News the video had “caused a lot of anxiety among our customers and made them uncomfortable.” The chain said it will add acrylic screens at some outlets to deter tampering on its conveyor belts, and said it would provide fresh seasonings and cutlery to those who request it.

Still, investors are concerned. Despite paring some of its earlier losses, shares in Food & Life remained some 4% down on Thursday.

The conveyor belt sushi restaurant format “was not designed for the era when individuals can post videos on the internet,” said Citigroup Inc. analyst Shuhei Oba in a note this week.

“We believe demand for cheap and delicious sushi will continue to grow longer term, but costs could increase as operators strengthen their response to such campaigns,” Oba wrote.

Restaurant chains were this week attempting to enforce stricter hygiene measures as older videos emerged and wall-to-wall media coverage inspired copycats. The latest target involved a man using a communal spoon to eat his meal at a popular udon chain in southern Kitakyushu city.

Spokespeople for two other major conveyor belt sushi chains, Zensho Holdings Co.-owned Hamasushi and Kura Sushi Inc., told Bloomberg News they were considering methods like deploying artificial intelligence and cameras to deter potential pranksters.

Sushi chains are facing an additional “weight of investment,” said Shun Tanaka, a restaurant industry analyst for SBI Securities Co. If businesses, already squeezed by having to maintain low prices, cannot maintain profitability, “it’s possible that the conveyor belt sushi business itself will disappear.”

--With assistance from Kurt Schussler.

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