As the COVID-19 pandemic continues to grow, and the virus continues to spread, the transmission risks of everyday interactions may become an ongoing concern.
A recent study from the University of Guelph looked at exposure to COVID-19 from high-touch surfaces within grocery stores, and found that the risk is low if physical distancing guidelines and recommended cleaning protocols are followed.
SARS-CoV-2 is mainly spread through direct personal contact, respiratory droplets and bodily fluids. Recent evidence suggests that indirect transmission, i.e. touching inanimate objects or surfaces (fomites) exposed to the virus and then becoming infected by touching the eyes, nose or mouth, is rare but possible.
When lockdowns and quarantine protocols restricted activities, concerns about transmission were geared toward places the public could still visit, such as retail food stores. In these settings, there were concerns about possible transfer of the virus to customers via high-touch surfaces. Information about the presence, survival and infectivity of SARS-CoV-2, the virus that causes COVID-19, was limited on surfaces, particularly outside laboratory settings.
Surface selection and testing
We tested 957 samples at four Ontario food retailers over a one-month period, during the second wave of the virus. Because of the reported survival of the SARS-CoV-2 virus on various surfaces, we tested a range of high-touch surface areas accessible to both employees and customers.
The presence of SARS-CoV-2 has been reported on surfaces in environments with high viral loads, such as hospital wards and patients’ rooms. Viral persistence and ability to remain active depend on several factors such as airflow, temperature and relative humidity within an indoor facility.
The type of material the virus is exposed to can also affect persistence. Studies have found that SARS-CoV-2 was viable for four hours on copper, 24 hours on cardboard, and 72 hours on plastic and stainless steel. Another coronavirus – the human coronavirus strain HCoV-229E, which causes symptoms of the common cold – can survive for two hours to nine days on various surfaces such as metal, glass or plastic. Temperatures within 30–40 °C reduced viral persistence and survival.
Based on these data, high touch surface areas were identified in retail stores in four areas: payment stations, deli counters, refrigerated food sections and carts and baskets, as well as separations on a variety of surface types, including glass and plexiglass, metal bumpers. , plastic and metal handles.
Samples were collected in stores prior to daily operations and at the end of the working day to evaluate the public’s possible contribution to contamination of surfaces. The collected samples were stored in a cooler and transported for further processing and detection of viral RNA. Commercially available detection systems and reagent kits approved by Health Canada for environmental testing of SARS-CoV-2 were used to assess the presence or absence of viral RNA.
Presence of SARS-CoV-2 on selected surfaces
This study found that, regardless of store location (urban versus suburban), sampling day or time, surface location or surface material within the store, all samples tested negative for SARS-CoV-2 RNA, meaning that the values were below the detection limit of the method, which was also validated by control trials.
These results suggest that the risk of exposure from high-touch surfaces within the grocery store is low. This is dependent on the enforcement of retail outlets and implementation of physical distancing measures, regular sanitisation routines and systematic monitoring of the health of store personnel.
These results emphasize the importance of preventive measures to reduce the likelihood of encountering SARS-CoV-2 on surfaces commonly found and frequently touched in retail stores. This finding is in line with a recent study on the presence of SARS-CoV-2 on inanimate objects in hospitals. The study found that transmission of the virus through fomites is unlikely if cleaning procedures and precautions are maintained.
Next Steps: So What?
We believe that wearing a mask, maintaining physical distance, and cleaning and disinfecting contact surfaces significantly reduce the risk of transmission from surfaces to humans in grocery stores. These measures should continue even after vaccination because it is not known how contagious the newly emerging types are, and the extent of vaccination varies from place to place. It could be that the variants are less susceptible to disinfection or can be transmitted more easily.
Since it may not be possible to know the number of infected people in stores, the use of personal protective equipment and better cleaning procedures may be needed to ensure that future variants do not have unforeseen problems.