Covid-19 prevention: Don't forget to dry if you don't want hand washing to be a waste of time

Touching any surface with wet hands can also cause it to be recontaminated.

As the number of people infected with corona virus is increasing worldwide, the World Health Organization (WHO) continues to recommend that everyone should wash their hands frequently. You can wash your hands with soap or alcohol-based hand sanitizer.

But alcohol only works to inactivate the corona virus, but it does not necessarily remove dirt and other pathogens. Therefore, scrubbing hands with soap for at least 20 seconds is still recommended as the most effective method of disease prevention during the current Covid-19 epidemic.

However, in addition to misunderstanding the number 20 seconds and many people are washing their hands very lightly, health experts say there is one step of the handwashing process that most people are forgetting: They do not dry their hands. mine.

Covid-19 prevention: Don't forget to dry if you don't want hand washing to be a waste of time

A wet hand not only makes you uncomfortable, but also increases the load of germs that your hands can transmit back and forth between contact surfaces. Scientific studies have shown that pathogenic microorganisms have a higher chance of transmission on wet skin than on dry skin.

Wet hands transmit germs more easily than dry hands

That's the conclusion of a 2018 meta-review study published in the ofJournal of Infection Prevention by two authors: John Gammon, Associate Dean for Health and Human Sciences, Swansea University, and Julian Hunt a Research Fellow save here.

In this review, they examined 112 prior studies and selected 21 scientific articles that investigated the differences between a wet hand and a dry hand, and effective ways to dry it to limit the spread of the virus. transmit pathogens.

Prominent among these is the research by A. F. Merry at the Department of Anesthesiology at Green Lane Hospital in New Zealand and colleagues. In it, she tested seven different hand-drying scenarios, to test how much bacteria could be transmitted through them.

Scenarios include:

(1): A dry, unwashed hand.

(2): Hand wash under cold running water for 3 seconds, do not wipe or dry.

(3): Wash hands according to the discretionary procedure that participating volunteers usually do at home.

(4): Wash hands according to hospital procedures: Use soap containing povidone iodine or chlorhexidine for 3 minutes and dry with a sterile cloth.

(5): Hand wash under cold running water for 3 seconds, then dry with a hot air dryer for 45 seconds.

(6): Hand wash under cold running water for 3 seconds, then dry with a towel for 10 seconds and then dry with a hot air dryer for 10 seconds.

(7): Hand wash under cold running water for 3 seconds, then dry with a towel for 10 seconds and then dry with a hot air dryer for 20 seconds.

After the volunteers performed these scenarios, they were given four sterile plastic tubes to roll on their fingertips, simulating their contact with an intravenous catheter that would be inserted into the patient's body.

The tubes are then collected, dropped into sterile saline and centrifuged for 15 minutes to collect the bacteria. Each milliliter of water containing that bacteria will be grown in agar plates to see how much bacteria remains on the volunteer's hand after each touch.

And this is the result:

As you can see, a wet hand is the most terrible germ transmission agent. "Our data confirm the role of residual moisture on hands in influencing the level of bacterial transmission through touching surfaces. Hand moisture has never been taken seriously before, but it has implications. may undermine the benefits of hand-washing procedures," the authors wrote in the study.

Agreeing with this, Miryam Wahrman, author of the book "The Handbook: Surviving in a germ-ridden world" said that leaving hands wet after washing hands is a golden opportunity to help bacteria re-contaminate hands. friend.

"A damp hand touching a restroom doorknob is the perfect re-infection storm, leaving your clean hands covered with germs," Wahrman writes.

How should you dry your hands during the Covid-19 epidemic?

While Merry's research has convincingly demonstrated that the infectivity of a wet hand is much greater than that of a dry hand, the suggestion of drying hands with a towel and hot air dryer is not appropriate under this condition. current reality.

Some new studies have shown that using hot air dryers can help spread pathogens into the environment, although the dispersion is not as great as high speed dryers - using only cold air blowing at high speed. nearly 9 times higher than hot air dryer.

And reusable cloth towels also become a problem, because on them can be contaminated with bacteria and viruses.

"The findings highlight that hot-air dryers and cloth towels can be a problematic way of drying hands - especially in hospital settings," said John Gammon and Julian Hunt.

They cited a 2014 study published in the Journal of Hospital Infection that showed that high-speed cold air dryers can disperse dozens of pathogens within a radius of 1.5 meters. Less pathogens are released with hot air dryers, but they can still travel within 0.75 meters thanks to the blown air.

Using cloth and paper towels to dry hands will reduce air disturbances and limit the amount of pathogens spread within 0.5 meters:

"Studies show that drying hands with a tissue or cloth removes more bacteria than just washing hands, because the friction of drying reduces the number of bacteria even further," Wahrman said. know.

But if you use cloth towels, she says, you'll have to pay attention to a few things: They should only be used at home, where each person has their own towel and hangs it in place. Hand towels should be washed frequently, every few days if used heavily.

So Wahrman's advice is to use paper towels. A study in the journal The Society for Applied Microbiology also supports drying hands with paper towels, as it has been shown to be the most effective way to limit the spread of viruses.

Scientists built a dummy depicting children and adults, standing in different ranges to measure the amount of virus released by high-speed (circular) air dryers, warm air dryers ( square) and tissue (triangle) to it. As a result, using paper towels is safer:

John Gammon and Julian Hunt agree with these studies. They write: "Disposable tissues are recognized as the fastest and most effective way to remove residual moisture that can create opportunities for micro-organisms to spread. This is extremely important in any context. who are concerned about the spread of the corona virus."

"Our study serves as a timely reminder that proper and effective hand-washing is integral to hand hygiene, whether you're in the hospital, you're a surgeon art or just working in the office."

Meanwhile, Wahrman recommends during the epidemic season, you should carry a pack of clean tissues in your pocket. And especially note, paper towels used to wipe hands must be tough, absorbent and not crumbly. Otherwise, they can further contaminate your hands.

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