Black light experiment shows how quickly a virus like Covid-19 can spread at a restaurant

A viral video from Japan aims to show how easily germs and viruses can spread in restaurants when just one person is infected.

The experiment simulates the atmosphere at a buffet restaurant or on a cruise ship. It was conducted by the public broadcasting organization NHK in conjunction with health experts.

The video shows 10 people coming into the restaurant, with one singled outas an “infected” person. A fluorescent substance only visible under black light is applied onto that person’s hands, representing germs from a cough or a sneeze.Each participant then goes about the buffet as they normally would, not considering a potential contamination.

At the end of the video, the participants are cast under black lights illuminating where the “infection” has spread.

The substance, used to signify the germs, can be seen on food, serving utensils and platters, and even on the faces of some of the participants.

Japan has had 16,049 confirmed Covid-19 cases and 678 deaths, according to Johns Hopkins University data. More than 4.3 million cases of Covid-19 have been recorded worldwide, including at least 297,000 deaths.

Here’s what the experts have to say

While these kinds of experiments are not new, John Nicholls, a clinical professor in pathology at Hong Kong University, said they demonstrate how quickly a virus can spread, especially when hand washing is not performed.

“What the video demonstrated, is that it will spread to surfaces and to people very efficiently,” Nicholls told CNN, “and I think it really highlights the need of what people have been saying about hand hygiene to stop the spread of disease.”

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However, Nicholls said that the situation is “artificial” because there was so much fluorescent liquid on the “infected” person’s hands that it wouldn’t accurately reflect the amount of germs on someone’s hands.

Kentaro Iwata, an infectious disease specialist at Kobe University, agreed. He spoke about how coronavirus spread on the Diamond Princess cruise ship as an example.

“The experiment just described the possibility of the spread by contact, and that is not proof of what happened, so the distinction has to be clearly made between what could happen and what did happen,” Iwata told CNN.

NHK also did a second experiment where the simulated environment anticipated contamination and put in the necessary precautions. All of the participants, including the “infected” person, washed their hands before and during eating.

Frequently touched surfaces, such as serving utensils, were replaced or wiped down. When the participants went under the black light, none of the substance from the “infected” person had spread to the other participants.

But both experts said the experiment is a good way to show the importance of hand washing and hygiene.

CNN’s Bex Wright, Yoko Wakatsuki, Junko Ogura, and Mallory Gafas contributed to this report.