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.
21st October 2020 at 5:45 pm
Excellent work. Something we’ve been trying to tell the global community for the last 6 months now. From the pictures looks like DNA based RT-qPCR used for the analysis. As important as understanding the viability of the virus on surfaces and possibility for infection often less discussed is this technology being used for contact tracing. Whether the RNA of SARS-CoV-2 virus in viable or not you can guarantee one thing, someone with the virus has been in contact or vicinity of that location. Call it a mass screening tool where it’s not required to stick a swab up everyone’s nose. Promising also to identify through screening asymptomatic cases.
Key here is the discussion and research. More we know, the better tools and strategies that can be employed for everyone’s safety. Pity DHS’s that should be leading the charge to protect the community in Australia are not so open minded. Guess they know what they know and they don’t know what they don’t know.
21st October 2020 at 4:43 pm
Good work by CSIRO team
I am happy to note that virus survives for less time in warm weather. It will be good to understand that mouth wash and gargles can reduce the transmission from infected person to normal person if both persons are following such oral hygiene.
There are also claims that steam inhalation can help to mitigate the covid virus infection, so if some one inhales steam, even though the water vapour admixed with air and may be at 40-45 deg C, this encourages me to believe that viral load can be reduced.
21st October 2020 at 3:44 pm
Although the numbers of sick people have overwhelmed many of the worlds medical facilities, this virus could have been a lot worse ie higher mortality rate or killed the young. So the more that can be learned in infection control the better. We do not live in sterile environment and we cannot live in a sterile environment – so it is a matter of managing the risks and being sensible.
21st October 2020 at 3:36 pm
As the results above indicate from the beginning of this epidemic – your skin protects you – gloves need only be used if you have cuts on your hands or you are protecting your skin from particular washing detergents.
More work needs to be done to show how effective soap solutions are against the virus, and to look at ways to minimize the use of the costly solutions being marketed.
21st October 2020 at 3:22 pm
How long does he virus survive when subjected to direct and diffuse sunlight? How long does it survive under ultraviolet light of various wavelengths? If UV works, this information could be used to design UV sterilizers for escalator handrails and for moving rubber belts at supermarket checkouts. It may mean that the virus is less transmissible at outdoor venues such as beaches, fishing spots and outdoor sporting events.
22nd October 2020 at 12:28 pm
There have been studies looking at virus inactivation with UV. 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. More on this study is available here: https://academic.oup.com/jid/article/222/2/214/5841129