The virus that causes COVID-19, SARS-CoV-2, spreads primarily through respiratory droplets and aerosols expelled by an infected person. While airborne transmission is dominant, the virus can also transfer through contaminated surfaces, a process known as fomite transmission. Scientific evidence suggests that while surface contamination is possible, the actual risk of infection from touching an object like a grocery cart is low. Understanding this relative risk helps inform the simple, effective preventative steps people can take to shop safely.
Understanding Surface Contamination
The possibility of surface transmission begins with how the virus interacts with different materials. When an infected person coughs, sneezes, or speaks, respiratory droplets containing SARS-CoV-2 can land on nearby objects, such as a grocery cart’s handle. Materials commonly used for cart handles, like plastic and stainless steel, are non-porous surfaces that allow the virus to remain viable for a period of time.
Laboratory studies have shown that SARS-CoV-2 can be detected on plastic and stainless steel for up to two or three days under controlled conditions. Research found the virus remained infectious for up to 72 hours on plastic and 48 hours on stainless steel. These experimental conditions do not perfectly replicate the real world, where factors like temperature and humidity affect survival time. These findings establish that a grocery cart handle has the potential to harbor the live virus.
Assessing the True Risk of Fomite Transmission
Despite the virus’s ability to survive on surfaces, the actual likelihood of contracting COVID-19 from a grocery cart is very low. The Centers for Disease Control and Prevention (CDC) emphasizes that the principal mode of infection is exposure to respiratory droplets and aerosols carrying the infectious virus. Airborne transmission, especially in close contact settings, remains the primary focus of public health warnings.
Quantitative microbial risk assessments suggest that the chance of infection via surface contact is less than 1 in 10,000 for each touch of a contaminated surface. Fomite transmission requires stringent conditions: active virus must be present, a person must touch the surface, and then quickly transfer a high enough dose to their eyes, nose, or mouth. The amount of viable virus also decreases significantly over time; researchers found that after a few days, less than 0.1% of the starting viral material remained infectious. This low probability means the theoretical risk from a contaminated cart handle is significantly less than the risk posed by inhaling viral particles from an infected person nearby.
Preventing Virus Entry: The Role of Hand Hygiene
Preventing infection from a contaminated surface involves breaking the chain of transmission before the virus can enter the body. The virus must travel from the cart handle to your hands, and then from your hands to your mucous membranes—the eyes, nose, or mouth. This final step of self-inoculation is where preventative measures prove most effective.
Applying an alcohol-based hand sanitizer (at least 60% alcohol) or using a disinfectant wipe on the cart handle before shopping can reduce the amount of virus on the surface. Proper and frequent hand hygiene interrupts the transfer of the virus from your hands to your face. Washing hands with soap and water for at least 20 seconds is highly effective because the soap’s surfactants break down the lipid outer layer of the enveloped virus, deactivating it.
If soap and water are not available immediately after touching public surfaces, hand sanitizer is a good alternative. Shoppers should sanitize their hands immediately after finishing shopping and before touching their face or preparing food. Focusing on these simple, consistent actions is the most reliable way to mitigate the risk of surface transmission.