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Why does the CDC want you to hum Happy Birthday – twice?

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The Answer

Singing the Happy Birthday song takes about 10 seconds to sing. The CDC recommends washing hands for 20 seconds – about two times through the birthday song.

One of the best methods of preventing the spread of disease is frequent hand washing. Keeping your hands clean is even better than wearing a mask.

The Centers for Disease Control and Prevention (CDC) has been encouraging people to wash their hands well in an effort to minimize the spread of the Covid-19 virus.

For the latest information on the spread of Covid-19, check out their frequently updated Situation Summary.

The CDC has published a useful document on effectively washing hands.

Keeping hands clean is one of the most important steps we can take to avoid getting sick and spreading germs to others. Many diseases and conditions are spread by not washing hands with soap and clean, running water. CDC recommends cleaning hands in a specific way to avoid getting sick and spreading germs to others. The guidance for effective handwashing and use of hand sanitizer was developed based on data from a number of studies.

Show Me the Science – How to Wash Your Hands | Handwashing | CDC

Since most of us have been washing our hands several times per day since we were little, it’s easy to assume that we know what we’re doing. However, most of us probably aren’t doing so in a way that effectively removes germs.

In short, we should scrub the fronts and backs of our hands, including fingernails using clean running water – for at least 20 seconds. This is where Happy Birthday comes in.

Scrub your hands for at least 20 seconds. Need a timer? Hum the “Happy Birthday” song from beginning to end twice.

Show Me the Science – How to Wash Your Hands | Handwashing | CDC

We’re all lucky that a judge invalidated Warner Music’s claim on the copyright to the Happy Birthday song and it is now in the public domain. 🙂

Why is a 20-second hand wash better?

Washing hands with soap removes dirt and germs from hands. You might think that as long as you cover your hands with soap and then rinse the soap off would be just as effective as rubbing. It’s not.

Soap and water don’t kill germs; they work by mechanically removing them from your hands. Running water by itself does a pretty good job of germ removal, but soap increases the overall effectiveness by pulling unwanted material off the skin and into the water.

The handiwork of good health – Harvard Health

The phrase “mechanically removing” is the key part of the statement above. Rubbing the skin dislodges dirt and germs from the skin. The molecular properties of soap allows it to bind with those particles and the rinsing action of the water washes it all away. For a better explanation see How Soap Works on

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