(CNN) — Sushi train restaurants have long been an iconic part of Japan’s food culture. Now, videos of people licking shared soy sauce bottles and messing with plates of food on conveyor belts are prompting critics to question their prospects in a Covid-conscious world.

Last week, a video taken at Sushiro, a popular sushi chain, went viral, showing a male customer licking his fingers and touching food as it came down the rotating belt. The man is also seen licking a condiment bottle and a cup that he places back onto a communal pile.

The prank has set off a deluge of criticism in Japan, where such acts are becoming more common and being called “#sushitero,” or “#sushiterrorism,” online.

The trend has rattled investors. Shares in Sushiro’s owner, Food & Life Companies Co Ltd, fell 4.8% last Tuesday, as the video circulated.

The company is taking the incident seriously. In a statement last Wednesday, Food & Life Companies said it had filed a police report against the customer, alleging damages. The firm also said it had received an apology from him, and that it had instructed restaurant staff to provide specially disinfected utensils or condiment containers to any customers who felt uneasy.

Sushiro is not the only company dealing with the problem. Two other leading conveyor belt sushi chains, Kura Sushi and Hamazushi, told CNN that they had experienced similar disruptions.

In recent weeks, Kura Sushi has also gone to police over another video of a customer who picked up food with his hands and put it back onto the conveyor belt for others to eat. The clip appeared to have been filmed four years ago, but only recently resurfaced, according to a spokesperson.

Last week, Hamazushi reported its own separate incident to police. The chain said it had spotted a video widely circulating on Twitter, which showed someone dropping wasabi onto sushi as it rolled past. This “deviates significantly from our company’s rules, and is unacceptable,” the firm said in a statement.

“I think these incidents of ‘sushi tero‘ are happening because there are fewer staff in stores to keep an eye on customers,” Nobuo Yonekawa, a Tokyo-based sushi restaurant critic for over 20 years, told CNN. He added that restaurants had recently cut down on labor to cope with other rising costs.

Yonekawa noted that the timing of the pranks was especially sensitive, particularly as Japanese consumers continued to be more hygiene-conscious due to Covid-19.

Japan has a reputation for being one of the world’s cleanest places, where people wore face masks regularly even before the pandemic to prevent spreading of illnesses.

The country is currently experiencing a record wave of Covid-19 infections, with the number of daily cases peaking at just under 247,000 in early January, according to Japan’s public broadcaster NHK.

“In the time of Covid and in light of these incidents, conveyor belt sushi chains need to reevaluate their hygiene standards and food safety,” he said. “These chains will need to come out and present solutions to the customer to regain trust.”

Sensitive times

Businesses have good reason to be worried. Daiki Kobayashi, a Japan retailing analyst for Nomura, predicts the trend could weigh on sushi restaurants’ sales for as long as half a year.

In a note to clients last week, he said the videos at Hamazushi, Kura Sushi and Sushiro were “likely to weigh on sales and customer footfall.”

“ how critical Japanese consumers can be of incidents involving food safety, we think the negative impact on sales could last for six months or longer,” he added.

Japan has dealt with this issue before. In 2013, frequent reports of pranks and disruptive behavior at sushi restaurants also “dented” sales and traffic at chain operators, according to Kobayashi.

Now, the new videos are sparking a fresh debate online. In recent weeks, some Japanese social media users have questioned the role of conveyor belt sushi restaurants as consumers demand more attention to cleanliness.

“In this day and age where more and more people are aiming to go viral on social media, and the coronavirus has made people more sensitive to hygiene, a business model based on the belief that people will behave, like conveyor belt sushi restaurants, may no longer be viable,” one Twitter user wrote. “It’s sad.”

Another user likened the issue to those faced by buffet operators, suggesting that the pranks had “exposed” a problem with communal serving in general.

AI cameras and acrylic boards

For now, companies are taking drastic measures to ease concerns.

Last Friday, Sushiro stopped serving unordered food on conveyor belts altogether, in hopes of deterring people from touching others’ food.

Instead of letting customers grab plates as they wish, the company is now placing photos of sushi on top of empty plates coming down the belt, which show people what they can order, a Food & Life Companies spokeswoman told CNN.

Sushiro will also install acrylic boards between the conveyor belts and diners’ seats, to limit their contact with the food passing through, according to the company.

Kura Sushi is taking a different route. This week, a company spokesman told CNN that it would try to use technology to catch perpetrators.

Since 2019, the chain has outfitted its conveyor belts with cameras that use artificial intelligence to gather data on which kinds of sushi customers pick and how many plates each table consumes, he said.

“This time, we want to deploy our AI-operated cameras to monitor if customers put the sushi they picked up with their hands back on the plates,” the spokesman added.

“We are confident we will be able to upgrade the systems we already have in place to deal with these kind of behaviors.”

— Natsumi Sugiura and Moeri Karasawa contributed to this report.

‘Sushi terrorism’ prank videos in Japan are hurting their famous conveyor belt restaurants