Testing high contact surfaces in grocery stores for COVID-19

As the COVID-19 pandemic continues and the virus continues to circulate, the transmission risks of everyday interactions can become an ongoing concern.

A recent study at the University of Guelph examined the risk of exposure to COVID-19 from high contact surfaces in grocery stores and found that the risk is low if physical distancing guidelines and recommended cleaning protocols are followed. .

SARS-CoV-2 is spread primarily through direct personal contact, respiratory droplets and bodily fluids. Recent evidence suggests that indirect transmission, that is, infection by touching inanimate objects or surfaces (fomites) that have come into contact with the virus, and then touching the eyes, nose or mouth , is small but doable.

When lockdown and quarantine protocols restricted activities, concerns about transmission were funneled into spaces the public could still visit, such as retail food stores. In these settings, there were concerns about the potential transfer of the virus to clients via high contact surfaces. Information on the presence, survival and infectivity of SARS-CoV-2, the virus that causes COVID-19, on surfaces was limited, especially outside of laboratories.

Selection and testing of surfaces

We tested 957 samples at four Ontario food retailers over a one-month period, during the second wave of the virus. Due to the reported survival of the SARS-CoV-2 virus on various surfaces, we tested a range of high contact surface areas accessible to both employees and customers.

SARS-CoV-2 has been reported on surfaces in environments with high viral load, such as hospital wards and patient rooms. Viral persistence and the ability to remain active depend on many factors such as air flow, temperature and relative humidity in an indoor installation.

The type of material that the virus comes in contact with can also affect persistence. Studies have shown SARS-CoV-2 to be 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 common cold symptoms – could survive on various surfaces such as metal, glass or plastic for two hours to nine days. Temperatures between 30 and 40 ° C reduced viral persistence and survival.

Based on this data, retail store touch surfaces were identified in four areas: payment kiosk, deli counter, refrigerated food section and carts and baskets, as well as on a variety of types of surfaces including glass and plexiglass. partitions, metal bumpers, plastic and metal handles.

Samples were taken in-store prior to daily operations and at the end of the workday to assess the public’s potential contribution to surface contamination. The collected samples were stored in a cooler and transported for further processing and detection of viral RNA. A commercially available detection system and reagent kit approved by Health Canada for environmental testing of SARS-CoV-2 was used to assess the presence or absence of viral RNA.

Presence of SARS-CoV-2 on selected surfaces

This study found that regardless of the location of the store (urban or suburban), the day or time of sampling, the location of the surface in the store or the surface material, all samples were tested negative for SARS-CoV-2 RNA, meaning that the values ​​were below the method detection limit, which was also validated by control testing.

These results suggest that the risk of exposure from heavily touched surfaces in a grocery store is low. It depends on the application and implementation by retail stores of physical distancing measures, regular disinfection routines, and systematic health monitoring of store staff.

These results highlight the importance of preventative measures to reduce the likelihood of encountering SARS-CoV-2 on surfaces commonly found and frequently touched in retail stores. This finding is consistent with a recent study on the presence of SARS-CoV-2 on inanimate objects in hospitals. The study found that transmission of the virus by passive vectors is unlikely if cleaning procedures and precautions are maintained.

Next steps: so what?

We believe that wearing masks, maintaining physical distance, and cleaning and disinfecting contact surfaces significantly minimizes the risk of transmission from grocery store surfaces to humans. These measures are expected to persist even after the vaccinations are administered, as it is not known how infectious new emerging variants are and the extent of vaccination varies from location to location. The variants may be less sensitive to disinfection or may be transmitted more easily.

Since it may not be possible to know the number of people infected in stores, the use of personal protective equipment and improved cleaning procedures may be necessary to ensure that future variations do not cause unforeseen problems.