From the moment you turn off your morning alarm, to the time you hit the pillow, your life is full of surfaces. Swiping through your phone, opening doors, putting in your PIN – there are many you don’t think twice about touching.
But SARS-CoV-2, the virus that causes COVID-19, will likely change the way we all think about, and interact with, surfaces forever. Our peer-reviewed study published in Virology Journal reveals new information about the virus and how it behaves on surfaces.
Understanding SARS-CoV-2 on surfaces
From analysing sewage to testing face masks, our research has been contributing to the global battle against COVID-19.
At this stage of the pandemic, researchers do not fully understand the role contaminated surfaces play in the transmission of SARS-CoV-2. To improve our understanding of how this new virus behaves, our researchers studied the survival rates of infectious SARS-CoV-2, dried in an artificial mucous solution, on six common surfaces.
We conducted the experiment at three different temperatures, 200C, 300C and 400C, with the relative humidity kept at 50 per cent. The surfaces used in the study were stainless steel, glass, vinyl, paper and polymer banknotes, and cotton cloth. These are examples of high contact surface areas such as glass on touchscreens and stainless steel doorknobs.
A droplet of fluid containing the virus at concentrations similar to levels observed in infected patients was dried on multiple small test surfaces and left for up to 28 days. At various time periods, the virus was recovered and placed in tissue culture cells to observe if any infectious virus remained.
Impact of temperature on virus
At 20°C, the virus was extremely robust. We were able to recover infectious material after 28 days from the smooth (non-porous) surfaces. These are stainless steel, glass, vinyl and paper and polymer banknotes.
The length of time infectious virus was able to survive on the porous material (cotton cloth) was much shorter. On cloth, we were unable to detect any viable virus past 14 days.
At 30°C infectious virus did not survive beyond seven days on stainless steel, money (polymer banknotes) and glass. However, on vinyl and cotton cloth, infectious material was not detectable beyond three days.
At 40°C virus was inactivated much faster. Infectious SARS-CoV-2 was detectable for less than 16 hours for cotton cloth. While on glass, paper and polymer notes, and stainless steel it was detectable for up to 24 hours, and 48 hours for vinyl.
How many particles can cause an infection?
It generally takes more than one virus particle to infect a person and make them sick. We call the number of virus particles that can cause infection the “infectious dose”. This dosage differs between different viruses and is usually quite large.
Researchers do not yet know the infectious dose of SARS-CoV-2. But, from our knowledge of related viruses, we estimate it is around 300 particles. If the virus was placed (on smooth surfaces) at standard mucus concentrations of an infected person, enough virus would easily survive for two weeks to be able to infect another person.
Further research on this topic is necessary. However, our findings indicate the 28-day sample would not contain enough viable virus to infect a person.
Whether virus particles on a surface can infect someone is dependent on several conditions. Outside of the body, SARS-CoV-2 virus particles gradually become inactive over time. The time it takes for viruses to naturally inactivate depends on many factors. The makeup of the virus itself, the type of surface it is on and whether the virus is liquid or dried can impact the time it remains viable. Environmental conditions such as temperature, exposure to sunlight and humidity also play a part.
Cash or card? A droplet of liquid containing the SARS-CoV-2 virus on a $5 note.
How virus transmission works
In general, we know people deposit viruses onto surfaces by coughing or sneezing. They are also readily transferred between contaminated skin and surfaces.
The results from our study confirm that high-contact surfaces may pose a risk. These are the type of surfaces that have a significant number of different people touching them each day. They include bank ATMs, handrails, door handles, elevator buttons, supermarket self-serve check-outs and money.
While we can’t yet answer the likelihood of developing COVID-19 from surfaces, we do know the SARS-CoV-2 virus can’t penetrate skin. To catch the disease, you would first need to introduce the virus into your mouth, nose or eyes. Our findings reinforce the message that you should avoid touching your eyes, nose and mouth and keep washing your hands. It’s also important to be careful when removing facemasks as the virus can survive on the outside where you could transfer it to your hands.
Building our understanding of COVID-19
Although we still don’t know how much virus it takes to infect someone, our research is forming a better understanding of how this new virus behaves.
Our knowledge that the virus survives longer at colder temperatures may also help to explain the spread of SARS-CoV-2 in environments such as meat processing facilities.
Our research will help to provide insight into the risks associated with COVID-19. And can help with the development of procedures for minimising the chances of virus spread via surfaces.
5th November 2020 at 11:09 pm
Hi guys. You must to do the experiments with different relative humidity, because the humidity can be a key to the spread to the virus and a key in the survival time, because affect his lipidic cover.
31st October 2020 at 10:31 am
Is there something you can wipe a surface with that leaves a long-lasting film/residue that destroys quickly any virus that lands on it? Perhaps tea-tree or eucalyptus oil.
20th November 2020 at 11:45 am
We are not aware of any product that can remain on a surface and destroy the virus. From other studies we have performed, we do know that tea tree and eucalyptus oils are not effective at inactivating the virus.
We know that solutions with 70% – 80% alcohol are effective at inactivating the virus.
28th October 2020 at 1:12 pm
Thanks for that information. When covid first arrived I stopped using money…preferring to go contactless. Must confess I was getting a bit slack with hand washing and started using money again. It’s pretty obvious that even with very low case numbers, money may go through lots of hands within that survivability window. And it may be that it only takes the right conditions for it to spread the infection.
Back to contactless and back to handwashing.
27th October 2020 at 5:27 pm
I don’t see this here, but it is mentioned in the Riddell et al. 2020 article mentioned above (second column on page 5 of the PDF):
The survival time for the influenza A virus (the most common flu virus) at room temperature is up to 17 days,
so covid-19 survives a lot longer.
25th October 2020 at 3:14 am
Hello! Thanks for sharing this research. After reading it I wondered somethings: were these experiments carried out in a dark room or just a room in the shadow but with indirect light (i.e. inside our homes)? Recently The Lancet and Jama released studies where the virus wasn’t found beyond 14 days. The Lancet said the virus could survive up to 14 days in our fridge and Jama said it could survive up to 9 days in steel. With that being said I wonder if indirect sunlight (i.e. the light that illuminates our homes) would also degrade the virus as the fridge is a dark place most times but we open it sometimes to get our food. Also, I was thinking about spreading the virus from surface to surface and how that affects the quantity of infectious copies. If I have several copies of the virus in my hands then the more surfaces I touch then the less copies will be left in each surface ¿Right? So, if I enter my house and I take off my clothes then the more I touch my clothes the less virus I’ll have in my hands and if I don’t use gel or soap I’ll still leave some copies of the virus around my house but each time I touch a surface then less copies will be left and maybe the indirect light will affect the life span of the virus. Have you thought about that escenario?
20th November 2020 at 11:36 am
Hi Victor, many factors such as exposure to sunlight, heat and humidity plus the initial concentration of virus all influence the survival of virus on surfaces. For this reason, our studies were carried out completely in the dark, to avoid these variables – our focus was just on the effects of temperature on virus survival on different surfaces.
There have been studies looking at virus inactivation with ultra violet light (sunlight).
One study reported the following findings: Ninety per-cent of infectious virus was inactivated every 6.8 minutes in simulated saliva and every 14.3 minutes in culture media when exposed to simulated sunlight representative of the summer solstice at 40°N latitude at sea level on a clear day. Ref:https://academic.oup.com/jid/article/222/2/214/5841129
The initial concentration of virus on a surface does influence how long infectious material can remain. Yes, in theory, if the concentration of virus initially deposited on a surface is lower, then the amount of time that you will be able to detect viable virus will also be less.
You can even calculate this, by applying the D-value we have determined.
Your question about the effect of spreading virus around is an interesting one. And the answer depends on how much virus is needed to infect you. And this is purely theoretical!
If, for example, it takes 1000 virus particles to infect you and you picked up 10,000 virus particles on your hands, the more you spread those 10,00 particles around, the less likely it is that you will be exposed, at any point, to a sufficient amount of virus to infect you. But, if it only takes one virus particle to infect you, you might actually be increasing the risk of infection.
We do want to stress – the risk of being infected by contact with surfaces in much, much less than contact with an infected person and becoming infected by breathing in the virus. Our study showed that the risk is not zero, so keep washing your hands and don’t put your fingers in your mouth or eyes.