You’ve had your suspicions, and you’ve cast many a side-eyed glance at your fellow restroom patrons when they skip the sinks and head out the door. But a new study says even if you do wash your hands after using the bathroom, 95% of us aren’t doing it long enough to kill harmful bacteria. In essence, we’re all totally grody germ-spreaders.

Researchers at Michigan State University sent out trained student spies to observe bathroom hand-washing behavior, and found that only two in three people are using soap while one in 10 skip the sink altogether. Men are dirtier culprits, notes Live Science: Only half of men used soap and 15% didn’t wash their hands at all.

That, compared to the 78% of women observed who scrubbed up with soap and 7% who ditched the idea of cleaning themselves altogether.

And even if you are sudsing up and rinsing off afterward, bathroom users are only washing hands for six seconds. Only 5% washed their hands for 15 seconds or longer — about the time recommended by the Centers Disease Control, or enough time to sing “Happy Birthday” through twice.

It might not be all your fault, however: If the sink is dirty, that can cause people to pass it up altogether, in comparison to a shining bastion of cleanliness that will convince people to spend more time washing up.

“These findings were surprising to us because past research suggested that proper hand washing is occurring at a much higher rate,” study researcher Carl Borchgrevink, a Michigan State associate professor of hospitality business, said in a statement.

Start singing that birthday tune next time you’re in the restroom, and if you hear someone else doing it, you’ll know you’re safe to high-five in hygienic celebration afterward.

Gross! Just 5 Percent of Bathroom Users Wash Hands Correctly [Live Science]

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