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.
13th October 2020 at 9:42 am
So Face masks are no longer a potential hazard but a definite hazard. Because disposable masks will have the live virus on them for 28 days!!.
So are bio hazard bins going to be provided across the country and in work places?
Will cleaning companies provide hazmat clothing to cleaners who have to dispose off the masks?
13th October 2020 at 12:06 am
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.
13th October 2020 at 2:32 pm
Hi Raimond, thanks for your comment. We are continuing to conduct research to improve our understanding of this virus, but it is impossible to study every aspect. There is already a great study by US colleagues looking at the effect of humidity on SARS-CoV-2 which you may be interested in: https://doi.org/10.1128/mSphere.00441-20.
Please note that the study does differ from ours and due to this has produced different results.
12th October 2020 at 10:28 pm
My wife and I may be referred to as the so called ‘granny killers” for not wearing a mask, but then again my wife at 87 with heart failure and other underlying health problems (last year in hospital for it all in ICU) somehow consider to be safer as we do then to infect ourselves. My view is, that more than likely the nursing home problems which after 270 days by long shot exceed the 14 days isolation my likely be the result of failure of proper housekeeping. There you got kitchen staff donning PPE and then go to the rubbish bin disposing of items and with the now contaminated gloved touch everything around the kitchen and so little wonder residents and staff become infected, more like the Legionaries Disease Bacterium issue. Neither my wife or I have fl vaccinations as they are more likely to be harmful for senior citizen and undermine the immune system. I view, I am likely in a better health condition if infected with COVID-19 then most others who have the vaccinations, etc. Also in nursing homes there is a considerable failure to provide nutritious food. Also not living in fear can also improve the immune system. Locking away the elderly depriving them of proper contact with their loves once also can be a killer. As I understand it a virus is not alive. It can however cause a lot of problems. Mask are useless as it is like trying to use wire fencing to keep mosquito’s out. Living a healthy lifestyle, what ever that might be for each particular person, is more than likely to prevent falling victim of the fear mongering and COVID-19. In my view lockdown’s/curfews and compulsory mask wearing are rather promoting a severe reduction of a persons immune system causing them more likely to become a victim of COVID-19. Don’t worry and be happy, might actually be a better treatment for everyone. Be positive minded.
12th October 2020 at 7:56 pm
Hi Csiro team,
firstly any research which contributes to the debate as to how the virus is transmitted is clearly helpful. According to your research the virus survives in certain conditions a considerable amount of time. The inference appears to be that therefore the virus is, or at least can be, transmitted long after an infected person has had contact with a surface such as door handles money and many others. This however contradicts the “Heinsberg-Studie” a German study which looked at the environment of highly infectious people i.e their home and work and took samples of hundreds of surfaces and found that whilst the virus was present on many surfaces it was not able to infect other people. It is in my opinion therefore important that you qualify your findings. You are as far as I can see not concluding that there is a high risk of contracting the virus of surfaces. General Hygiene should off course continue to be observed in any case. Greetings from Germany where its much colder than 20 degrees. Tomas Busse
13th October 2020 at 2:33 pm
Hi Tomas, thanks for your interest in our research.
While it is generally accepted that transmission via aerosols and respiratory droplets is the primary mode of infection, we need to understand how long the virus can remain viable on a surface to evaluate the risks of surface transmission. While it is still unknown what the infectious dose of SARS-CoV-2 is, it’s still important to understand the potential risks a contaminated surface may pose. As you have mentioned, good hygiene should always play a part in any disease mitigation strategy – washing hands, using hand sanitisers when available, cleaning of high contact surfaces and avoid touching your face are all important steps to help reduce the risk of infection.
12th October 2020 at 4:58 pm
Hi Dale, in general IT and industry speak, S.O.P is a Standard Operating Procedure. It’s actually an English term. I too am not a bureaucrat. Hope that helps!