Black light experiment shows rapid rate at which just one infected person can spread germs and viruses when eating out

Image of gambling. Credit: Freedom Master/

A black light Japanse experiment which has gone viral shows how easily germs and viruses can spread in a buffet environment when just one person is infected.

THE experiment was conducted by the public broadcasting organisation NHK in conjunction with health experts and shows 10 people coming into the restaurant, with one singled out as 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 up to the buffet and picks and chooses as they normally would, without thinking about a potential contamination.

At the end of the video, the diners are cast under black lights illuminating where the ‘infection’ has spread.

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

Clinical professor in pathology at Hong Kong University, John Nicholls said these experiments are not uncommon, but demonstrate how quickly a virus can spread, especially when hands aren’t washed.

“What the video demonstrated, is that it will spread to surfaces and to people very efficiently,” he told CNN.

However, Nicholls said that the situation is “artificial” because there was excessive amounts of fluorescent liquid on the “infected” person’s hands which wouldn’t accurately reflect the amount normally found.

Infectious disease specialist at Kobe Universit, Kentaro Iwata, referred to 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 the news channel.

NHK carried out a second experiment in a simulated environment where necessary precautions were put in place.

Everyone taking part, including the ‘infected’ person, cleaned their hands before and while eating, and surfaces and items, like serving utensils, were replaced or wiped down.

When the diners went under the black light, none of the substance from the ‘infected’ person had spread to the others.

This, said both experts, was a more effective experiment as it showed the importance of hand washing and hygiene.

Japan has had more than 16,000 confirmed coronavirus 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.

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Written by

Tara Rippin

Tara Rippin is a reporter for Spain’s largest English-speaking newspaper, Euro Weekly News, and is responsible for the Costa Blanca region.
She has been in journalism for more than 20 years, having worked for local newspapers in the Midlands, UK, before relocating to Spain in 1990.
Since arriving, the mother-of-one has made her home on the Costa Blanca, while spending 18 months at the EWN head office in Fuengirola on the Costa del Sol.
She loves being part of a community that has a wonderful expat and Spanish mix, and strives to bring the latest and most relevant news to EWN’s loyal and valued readers.

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