If you ever needed another reason to keep your hands washed, the results of a recent science experiment conducted at an Idaho elementary school should have you covered.

In November, around the start of flu season, teacher Dayna Robertson, 38, and behavior specialist Jaralee Metcalf, 23, helped students at Discovery Elementary School in Idaho Falls with a science experiment to show the effects of unwashed hands.

The pair took five slices of fresh, white bread — one was left untouched, removed from the bread packaging into a plastic bag. Another was touched by all of the 17 students’ hands and then placed in a plastic bag. Another was touched after the students had washed their hands with soap and water, and another after they had used only hand sanitizer. Lastly, a piece was wiped on a classroom laptop.

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A month later, the results were in. The control remained mold-less, while the piece touched with clean hands appeared the same.

But the slices touched by dirty hands and hand sanitizer were another story: Yellow and black mold had begun to take over the bread. The worst offender of them all was the slice wiped on the laptop. Nearly four weeks later, it was almost entirely black with mold. (The educators told TODAY that the laptops are regularly wiped down and cleaned, but the one used in the experiment was not.)

“As somebody who is sick and tired of being sick and tired of being sick and tired. Wash your hands! Remind your kids to wash their hands! And hand sanitizer is not an alternative to washing hands!! At all!” Metcalf captioned the now-viral Facebook post, which had 64,000 shares and 17,000 reactions as of this writing.

Roberston, speaking to TODAY, said the students thought the results were “gross” and have since “really turned their hand-washing around.”

"Clearly the nagging didn't work, so we needed a more hands-on approach to get it figured out, but it worked,'' Robertson added. "They are taking the initiative themselves."

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Metcalf told the outlet that other teachers across the country have since said that they, too, will conduct the experiment, which was inspired by the University of Michigan-affiliated C.S. Mott Children’s Hospital.

“It's kind of cool to see that it's inspired a lot of other people to take a look at how they wash their hands to keep healthy,” she said, adding that unwashed hands can affect more than just one person.

“I've missed five or six days of school already because of my illness or my son's illness," Metcalf told TODAY. "When kids don't wash their hands, it takes a toll not just on us as teachers, but also on our families.”

"Safety over attendance,'' she continued. "Some of those [illnesses] can be dangerous to students and others. We have staff whose parents have cancer and are immunocompromised, so for them to bring illnesses home to them, it can be life-threatening."

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Late last week, the Centers for Disease Control and Prevention (CDC) in a new report said there have been at least 2.6 million flu illnesses this year and 23,000 hospitalizations. Some 1,300 people across the U.S. have died of the flu so far this year.

Most of the illnesses this year have been caused by the influenza B/ Victoria viruses, which the CDC said is “unusual for this time of year.” This strain is most commonly reported among children 4 years of age or younger, according to the report.