Bare feet are much less a risk for COVID-19 than shoes are

[This article will be updated regularly as new information becomes available.]

Being barefoot during the current COVID-19 crisis poses no particular risk of catching or spreading the coronavirus any more than dressing any other way. In fact, it poses even less risk of spreading the virus than shoes do, as will be explained below.                                                      

The world is currently experiencing a COVID-19 pandemic

As this article is published, the United States and the rest of the world are currently facing the outbreak of the disease COVID-19. To date [updated 11/22/20], this pandemic has affected 58.9 million people worldwide and resulted in 1.4 million deaths, with the U.S. having more cases than any other country. The U.S. and many other countries are under states of emergency.

An abundance of information has been made available by scientists and medical authorities as to how this disease is acquired and spread, as well as steps people need to take to help prevent its spread. Unfortunately some misunderstandings and confusion still abounds.

There is no specific information available about any role that bare feet may play as related to the coronavirus

One topic that has not been addressed by anyone at all – until now – relates to what role bare feet might play in the contraction or spread of the coronavirus that causes COVID-19.

I hope to provide some useful information about that, as well as put some of these issues into reasonable perspective. This information will be helpful to not only those who choose to live totally barefoot, but to anyone who may choose to not wear shoes occasionally in public.

Coronaviruses in general have been around for many years

First, a little information about coronaviruses in general. Coronaviruses are a particular group of viruses that can infect humans and animals. Their name comes from crown-like spikes on their surface.

These viruses can cause a common cold or a more serious disease, including Middle East respiratory syndrome (MERS), severe acute respiratory syndrome (SARS), and the novel (new) coronavirus disease 2019 (COVID-19).

COVID-19 is caused by the virus that has been specifically named SARS-CoV-2. It first appeared in Wuhan, China in late 2019. Symptoms usually occur within 2 to 14 days of exposure, and include fever, cough, and shortness of breath.

More serious symptoms can occur, usually when people have other medical conditions, including pneumonia. Some cases can result in death. There is no known cure or vaccine for it at this time.

The coronavirus is spread mainly by person-to-person close contact 

According to the CDC, the virus is mainly spread by respiratory droplets in the air produced from an infected person as they cough, sneeze, or talk in close proximity with another person (within 6 feet). These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into their lungs.

From the CDC:

The virus does not spread easily in other ways
It may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes. This is not thought to be the main way the virus spreads, but we are still learning more about this virus.

The COVID-19 coronavirus viability outside the body varies depending on the surface it’s on

A recent study was done to determine how long the novel coronavirus (SARS-CoV-2) can survive (remain viable) on various surfaces or environments.

A research study published March 17, 2020 in the New England Journal of Medicine,Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1,” by researchers at the NIH, the CDC, and multiple universities, compared the novel coronavirus (SARS-CoV-2) with SARS-CoV-1, the most closely related human coronavirus, and which was responsible for the 2003 epidemic.

This study found that the stability of novel coronavirus (SARS-CoV-2) was similar to that of SARS-CoV-1 under the experimental circumstances tested.

The findings from the study as to how long the novel coronavirus can remain viable and infective were as follows:

Stainless steel – 3 days
Plastic – 3 days
Cardboard – 24 hours
Copper – 4 hours
Aerosol (Air) – 3 hours

[Update 4/8/20]  An even newer study, entitled “Stability of SARS-CoV-2 in different environmental conditions,” published on April 2, 2020 in the British medical journal The Lancet, tested similar, plus a few more, surfaces as the previous study. This study found similar results for porous materials, but some longer virus viability time durations for nonporous surfaces.

Those findings were as follows:

Outer layer of a surgical mask – 7+ days
Inner layer of a surgical mask – 7 days
Plastic – 7 days
Stainless steel – 7 days
Glass – 4 days
Paper money – 4 days
Cloth – 2 days
Wood – 2 days
Cardboard – 24 hours
Copper – 4 hours
Paper & tissue paper – 3 hours

This study also confirmed previous findings that higher humidity levels and higher temperature levels reduce the time duration of viability of the virus. The inconsistent and unexpected finding for the surgical masks was not explained in the study.

The hardness or porosity of the surface seems to determine how long the coronavirus can survive on it

What is apparent here is that, generally, the harder or more nonporous the surface, the longer the coronavirus can survive on it. One could extrapolate the study findings above to suggest that most any nonporous surface would facilitate a longer infective period for a coronavirus than a porous surface would.

Here are some other examples of nonporous and porous surfaces. Not all items on the lists are equally nonporous or porous.

Nonporous materials
       Porous materials
Ceramic
       Cardboard
Chalkboard
       Fabric
Glass
       Leather – untreated
Leather – treated for shoes
       Paper
Metal
       Pumice
Plastic
       Skin
Porcelain
       Soil
PVC
       Sponge
Rubber
       Wood – untreated
Stainless steel
Tile
Vinyl
Wood – varnished

Copper is the exception; the coronavirus doesn’t survive very long on copper

You may have noticed the one glaring exception to the comparative viability of coronaviruses based on surface hardness (or porosity). Why does it survive for such a relatively short time on copper – a very nonporous metal?

The reason is that copper has been found to have its own antimicrobial properties, which have been seen even in ancient times. And that apparently helped to kill off the virus on its surface in the study.

Higher temperatures and higher humidity also limit the life of coronaviruses

Two other important factors, temperature and humidity, also affect the length of time coronaviruses are viable and infective. Higher temperatures and higher humidity both have been found to reduce the length of time that coronaviruses can survive outside the body. A number of studies have confirmed this.

One such study, “The Effects of Temperature and Relative Humidity on the Viability of the SARS Coronavirus,” was published in 2014 in Advances in Virology.

From the study:

In this study, we showed that high temperature at high relative humidity has a synergistic effect on inactivation of SARS CoV viability while lower temperatures and low humidity support prolonged survival of virus on contaminated surfaces.

Viruses very similar to the new coronavirus have been found to survive for about an hour or less on human skin

The new coronavirus has not yet been tested to see how long it would remain viable on unwashed bare skin, but several similar viruses have been tested, including CoV 229E, influenza A (H1N1 and H3N2), RSV, and others.

These tested viruses are similar to the novel coronavirus in many important aspects. They are all respiratory, that is, affect the lungs, and all cause flu or flu-like conditions.

The most significant similarity is that, like all coronaviruses, they are “enveloped.” That is, they have a lipid (fatty) bilayer on their outside. Unlike “nonenveloped” viruses, this lipid bilayer makes them significantly more susceptible to environmental conditions.

The lipid bilayer is why washing with soap is so effective against SARS-CoV-2 (and all other enveloped viruses); the soap dissolves that layer, rendering the virus noninfectious.

The most recent study, not yet officially published, was reported by Dr. Sayed Sattar, Professor Emeritus of Microbiology at the Faculty of Medicine at the University of Ottawa. Dr. Sattar and his research team studied the coronavirus CoV 229E, one of the viruses that causes the common cold.

In the January, 2020 article entitled “Human Pathogenic Coronaviruses: Understanding Their Environmental Survival For Better Infection Prevention And Control,” published  in InfectionControl.tips, Dr. Sattar reports that the CoV 229E coronavirus was found to retain its viability on the skin of human hands up to about an hour.

In another study, published in 2014 as “Survival of influenza virus on human fingers,” in Clinical Microbiology and Infection, the researchers found that the influenza viruses being tested remained infective for only up to 30 minutes on human skin (fingers).

An older study, “Possible Transmission by Fomites of Respiratory Syncytial Virus,” which was published in 1980 in The Journal of Infectious Diseases, found similar results. The RSV viruses tested remained infective on hands for only up to 25 minutes.

Bare skin seems to be the least hospitable place for the coronavirus to remain viable

Though the survival duration of the novel coronavirus itself has not been tested specifically on human skin, all the available evidence strongly suggests that bare skin is likely the very least hospitable surface for any coronavirus to come into contact with. Earlier studies, as mentioned above, found that similar viruses lose their infectiveness after about one hour or less on human skin.

Human skin also meets several other criteria as being a very unfavorable environment for coronaviruses to survive. It is very warm, it is moist, it is soft, and it is porous.

The coronavirus is respiratory and cannot penetrate and invade the body through the skin

Though skin is indeed porous, coronaviruses, like other microbes and pathogens, cannot penetrate skin to absorb directly into the body. It is a respiratory virus whose main way of infecting is to be breathed in after an already infected person sneezes, coughs, or exhales nearby.

Infection can also occur by a hand or other body part that has viable coronavirus on it directly touching the face, especially the nose or mouth, and thereby finding a path into the respiratory system and lungs.

Of course, washing the skin – hands, for example – with soap and water or using a sanitizer with at least 60% ethanol (alcohol) will immediately kill coronaviruses. And that is wise advice for hands, as the hands touch many surfaces as well as faces and other people.

Note, some hand sanitizers being sold are “alcohol-free”; those are not nearly as effective as alcohol or ethanol based sanitizers.

Bare feet are unlikely to spread the coronavirus as they touch nothing except the floor

Bare feet, unlike hands, touch nothing at all except the floor or other surface that’s being walked on. They aren’t going to touch faces, other people, food, or anything else that hands usually touch.

So, not only would any coronavirus that might have come into contact with bare feet die off fairly quickly – most likely in an hour or less – the feet aren’t going to spread the virus by touching anything above the floor. And bare feet get washed regularly.

Shoes are made from mostly nonporous materials, so coronaviruses will remain viable on them much longer than on bare feet

Shoes come into contact with the same surfaces that bare feet do. But shoes are constructed from various materials that, for the most part, are nonporous, thereby allowing possible coronaviruses that may get on them to remain and thrive for a relatively long period of time – even days.

Soles made out of rubber, for example, being very nonporous, could harbor infectious viruses for up to 3 days or longer.

Other materials that many shoes are made from, such as tanned and waterproofed leather, PVC compounds, and various plastic materials, are similarly problematic for allowing coronaviruses and similar microbes to thrive on them over a substantial period of time.

Several scientific studies have proven that various bacteria and other pathogens do attach themselves to shoes, particularly the soles of shoes, and remain on them for extended periods of time.

The most well-known and quoted study was done in 2008 by Dr. Charles Gerba, microbiologist and professor at the University of Arizona. He and his research team tested new shoes that had been worn by 10 participants for 2 weeks.

They found large numbers of bacteria both on the bottom and inside of the shoes; averaging 421,000 units of bacteria on the outside of the shoe and 2,887 on the inside.

Another more recent study in the U.K. by Ravel (footwear company) in 2019 found similar results.

Shoes are never washed, all the more reason that infective viruses will remain on them for a long period of time

Another interesting part of Dr. Gerba’s study was that after the shoes were worn and tested, they were then washed. The scientists washed the footwear in a standard washing machine using conditions suggested by the manufacturer, which included cold water and regular detergent. After washing, they found the bacteria on the shoes were reduced by 99% on the outside and 90% on the inside.

In the real world, however, shoes are almost never washed. Not only that, those unwashed shoes are touched and handled by bare hands as they are taken off or put back on daily, or more often. Another opportunity for any coronaviruses lingering on unwashed shoes to transfer to hands.

Bare feet, unlike shoes, are washed on a regular basis.

Bare feet are usually not touched by hands unless they are being washed. And by that time, any coronaviruses that may have come into contact with the feet during the day are most likely dead and gone anyway.

So, all things considered, being barefoot when out and about in public during this pandemic is a safer choice than wearing shoes. Neither shoes nor bare feet are very likely to help spread the coronavirus to other people, since neither is likely to touch faces or other people.

But by comparison, even if feet do come into contact with viable infective coronaviruses on the floor or ground, they are much more likely to survive for longer periods of time on shoes than on bare feet, and therefore have a greater chance of being spread to other people by shoes than bare feet.

The public knows little to nothing about how the coronavirus is actually spread

The problem comes in when most people don’t fully understand the virus and how it’s spread – what’s risky and what isn’t. Currently, there’s a plethora of information available about the coronavirus and COVID-19 on both the internet and popular news media.

But, except for very technical scientific information that most people aren’t likely to read, what you see or read seems to be the same thing  over and over. “Don’t get close to other people, and wash your hands frequently.”

That advice is excellent – and should be followed – but it also leads people often to conjure up in their own minds other irrational fears that really aren’t justified.

They may think, “If hands need to be washed often to stop the virus spread, then bare feet, which may appear dirty and not washed, would probably be even worse than hands for spreading the virus.”

Of course, such thinking is irrational and completely false. But how do you deal with such thinking in case someone actually confronts you and makes the claim that your bare feet are spreading the coronavirus?

Don’t be intimidated by the unfounded fears of others

Here are a few suggestions in case you run into such problems while out and about barefoot:

Let’s say someone says, “You need to have shoes on because your bare feet are going to spread the coronavirus,” or something similar.

A few possible responses (these, or any variation or combination of the ideas below):

“That’s not how it works. It’s a respiratory virus spread by droplets in the air. You don’t catch it from somebody’s feet. This is no time to be spreading misinformation.”

“It’s hands that could spread the virus, because they touch everything and then touch faces. Feet touch nothing but the floor.”

“If you think bare feet will spread the virus, what do you think shoes will do? They both touch the same surfaces. But shoes are actually worse, because they never get washed like bare feet do.”

“Viruses like the coronavirus won’t survive on bare skin for more than an hour or less. Scientific studies have proven that. It could live for days on shoes. My bare feet are safer than any shoes could ever be.”


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Julian Toussaint

An informative, very well reasoned and balanced article Kriss, complete with some great practical advice. Thank you for this post. I do hope such messages spread and are understood in this time when many react in panic and irrational fears manifest. Thank you for the post

tobias köhler

Interesting and well researched. But what is it about porous surfaces that lets the virus die more quickly?
I’m now scrubbing all four paws with soap as the first thing when I come home.

tobias köhler

Thank you. I think though that it cannot be compared directly: Skin is not a dry surface, it’s slightly moist (we have sweat glands). So the virus might not dry out. It won’t enter the body and the epidermis can’t be affected by this virus (there are other viruses causing skin problems such as warts or herpes), but it might find conditions to survive on the outside of the skin. Soapy water will dissolve the membrane and if washing hands is a good remedy against viruses, washing feet will do the same. (Hence my ritual sitting on the edge of… Read more »

Kent

Excellent piece! Great work my friend!

Hobbit

Moisture can’t be the only factor. If humidity deactivated virions, how would
they hold up at all inside pulmonary passages lined with mucus??

Neil C

Once again Kriss you inform the misinformed. When reading the title, I thought as a barefooter, my bare feet were a non issue which of course is true. You point out, however, that despite shoes also being pretty much a non issue, bare feet are even less of a threat to spreading the pandemic. Hand washing, wearing mask in public and keeping safe distance from others of at least 6 feet is our best strategy so far. I was hoping that with the threat being respiratory in nature, people would start to realize how my bare feet are not the… Read more »