University Post
University of Copenhagen
Independent of management


How much virus is there in the supermarket, in the gym, and on the city benches?

Virus — Did you know that you might pick up your next bout of flu from a cash dispenser? Two medical students helped set up a study that looks at where we get infected with influenza and other viruses.

If you touch the credit card machine in the supermarket or the gym’s exercise machine you may be up for an infection.

At the peak of the coronavirus, you may have realized that you risked getting infected by touching these kinds of surfaces. But it is only now that research has really begun to look at viruses on surfaces that can act as sources of infection in public spaces. Scientists now know that they can lead to infection through indirect contact, which is contamination via surfaces.

Johannes Roth Madsen and Jacob Pohl Stangerup Nielsen study seventh and eighth semester medicine, respectively, at the Faculty of Health and Medicine at the University of Copenhagen.

For one week last winter in the period 2-8 February 2022, they looked for virus residues from Sars-Cov-2 (coronavirus) on a total of 357 surfaces in Copenhagen.

By doing so, the two medical students helped launch a new project with six other researchers to find out how people infect each other indirectly.

Found evidence of coronavirus on surfaces

»The study has proven that coronavirus can sit as particles on surfaces that we touch in the course of our daily lives,« says Johannes Madsen.

The study found that 42 per cent of all of the examined credit card machines in supermarkets and in other places had RNA from Sars-Cov-2 on their surfaces. The Rejsekort travel card machines in public transport had remnants of it in 40 percent of cases.

The two medical students are surprised about this result, as no one needs to touch the travel card machines to check in. They don’t yet have a good explanation.

Offers perspective on influenza virus also

No previous Danish study has been done that shows how humans can be indirectly infected with Sars-Cov-2. There are, on the other hand, Danish studies on how we can be directly infected via, say handshakes, or when the infection floats through the air as droplets via sneezes from person to person.


You can only get infected with a virus as long as it is active. The coronavirus remains active for up to 72 hours. In the study, the researchers looked for RNA from the coronavirus on surfaces, and they found traces of it up to 21 days (the RNA does not need to be active to be found). Their method does not allow researchers to distinguish between active and inactive virus, and they therefore have not been able to determine the specific risk of infection from touching the examined surfaces.


Indirect transmission is when someone who is infected with the coronavirus first transfers the infection to a surface and then goes their own way. Then another person comes and touches the infected surface and gets the virus on their hands. When they then rub their eyes, nose or mouth, they get sick.

The same phenomenon applies to many other types of viral diseases, including seasonal influenza.

»We reckon therefore that it is easy to put our study into an influenza virus perspective, because it can sit on the same surfaces as the coronavirus and infect us from the same places,« says Jacob Pohl Stangerup Nielsen.

Supermarket’s hand disinfectant should be at the checkout

According to the two medical students, little is known about how we humans infect each other through indirect contact, and this was their motivation for doing the project.

»We wanted to find out how much virus there is on the surfaces in public spaces that contribute to indirect infection,« says Jacob Nielsen.

They offer suggestions for what the study can be used for in the future.

»We now know more about when it is a good idea to wash your hands. It could be after touching a freezer handle in the supermarket. We can see that you should at least not touch your mouth, eyes or nose before you have washed your hands,« says Johannes Roth Madsen.

In practical terms, there are some things that should be done differently in Denmark.


In addition to the two medical students Jacob P. S. Nielsen and Johannes R. Madsen, six researchers Kamille Fogh, Emma H. Mikkelsen, Emil Wolsk, Nikolai S- Kirkby, Henning Bundgaard and Kasper Iversen participated in the study. They were also helped by a number of other people who collected the samples.

The study is published in Open Forum Infectious Diseases and is called: »Sars-Cov-2 Surface Swabs in Locations With Public Access – Potential for Improved Sourced Control«

»Perhaps the hand sanitizer dispensers should be placed in other places in the supermarket. We can see that the surface of shopping baskets does not have nearly as much virus on it as the freezer handle further inside the store. And the credit card Dankort terminal by the checkout has the most. Perhaps it is more important that there are hand sanitizers inside the supermarket and right up by the checkout, instead of just one at the entrance,« says Jacob Pohl Stangerup Nielsen.

They both hope that their work, which has contributed to knowledge on where viruses settle, will help in guidance to fight a new epidemic.