Confronting COVID-19: An Analysis of Surface Contamination Risks

By Paul Benda

Officials from the Centers for Disease Control and Prevention have acknowledged that COVID-19 is a new disease and they are still learning how it spreads. Here I will outline the recent science behind the transmissibility of the virus that could lead to infection. While this is not intended specifically to address the unique challenges facing banks, it does contain information that all bank employees could find helpful in reducing risk to staff and customers, especially when they use an ATM.

The CDC believes that the primary spread of the virus is from person to person; specifically, those in close contact (within six feet) and through respiratory droplets expelled by a person through coughing or sneezing. However, the CDC states that it may be possible for a person to become infected by touching a surface or object contaminated with the virus and then touching their mouth, nose or possibly their eyes.

My goal here is to outline the recent science regarding the risk of infection from contaminated surfaces in an accessible manner. There are many unknowns and many variables around the ability to be infected through an indirect manner, which is why guidance from the CDC and others is always vague. This paper focuses on two different analyses, one from China that appears to show how transmission can occur in an indirect manner and the other from a recent New England Journal of Medicine study on the surface stability of SARS-CoV-2, the novel virus that causes COVID-19. Using these two papers as baseline, the following can be concluded:

It is possible to be infected with SARS-CoV-2 through indirect transmission, but it appears to be exceedingly rare, and a whole series of factors must occur to make it happen.

With proper precautions, you should be able to minimize your risk (to near zero) from indirect transmission when you go outside your house. (This paper does not address the risk from droplet or aerosol-based infection which is why social or physical distancing is still important and people exhibiting symptoms should be avoided.)

Packages and shipments you receive are likely safe without any additional action.

For standard U.S. Postal Service mail, UPS or FedEx shipments, the risk is de minimis. If it is a same-day delivery, it is still likely safe, and if left to sit for 12-24 hours at room temperature the risks become de minimis as well.

For takeout or near real-time food delivery, the likelihood of significant contamination being on the package is still very low, especially if prepared by asymptomatic personnel, but out of an abundance of extreme caution wiping down the high-touch parts of the packaging with an approved cleaner and then washing your hands, likely reduces the risks to near zero.

Items brought home such as groceries and office supplies are likely safe.

After airborne/droplet transmission, the highest risk appears to be from high-touch surfaces such as bathroom fixtures, door handles, shopping cart handles, etc. Handle those types of interactions carefully. If you can, wipe them down before use. If you cannot, recognize after you touch them that your hands, even though very unlikely, may be contaminated. This is okay as long as you don’t touch your face and provide the virus a path into your body.

Continue your shopping trip, making sure not to touch your face, but prior to getting back in your car or touching a surface you own, sanitize your hands and/or remove whatever gloves you have on. If you are carrying shopping bags, load them first, preferably not through the driver’s door. Then take off your gloves or sanitize your hands (and car key if used to open the door) prior to opening your driver’s door. This ensures your hands are clean and you won’t transfer virus to your door handle or, more importantly, your steering wheel.

How likely is it that I’ll get coronavirus from a contaminated surface?

There are a lot of news articles based upon a limited number of studies that discuss with alarm how the virus can be found on surfaces one day, four days or even weeks later. It is useful to think about how you get sick from a contaminated surface. You need three things:

You need to transfer the virus from a contaminated surface onto yourself, most likely bytouching something with your hand.

You need to transfer the virus from your hand into your body. For SARS-CoV-2 it is believedto enter through your eyes, nose or mouth.

You need a sufficient amount of the virus to enter your body to actually make you sick.

While there are a limited number of studies on infectious dose-rates that use measures such as a 50 percent tissue culture infectious dose (TCID50) or plaque-forming units to measure the amount of virus to make you sick, it is likely that it will require a significant number of virions (potentially thousands) to make you sick with the virus.

For each of those steps, the amount of virus being transferred gets decreased as no transfer mechanism is 100%, so, if you work backwards to step one, someone sick needs to leave on a surface a substantial amount of viable virus—meaning it is infectious and can make you sick.

Those two items are key and should drive how you consider risk mitigation techniques, and what it means when an article says the virus can be found on the surface three days later. Is the virus viable or does just the RNA remain of a “dead” virus? Is it in substantial quantity or only trace amounts? “What’s getting a lot of press and is presented out of context is that the virus can last on plastic for 72 hours—which sounds really scary,” says Carolyn Machamer, a professor of cell biology at Johns Hopkins School of Medicine, who has studied the basic biology of coronaviruses for years. “But what’s more important is the amount of the virus that remains. It’s less than 0.1 percent of the starting virus material. Infection is theoretically possible but unlikely at the levels remaining after a few days.”

The important thing to remember is that the virus does degrade over time and at a substantial rate, so the one thing that can be said unequivocally is that the risk from surface contamination goes down over time at room temperatures.

As we know people can get sick via fomites, but it appears to be very rare and is likely a combination of a perfect storm of a large amount being deposited, someone coming into contact with it after a relatively short period of time, and then creating a pathway into the body.

Case study: Using a bank drive–through ATM

Looking at the previous analysis, what are the concerns in completing a transaction at an ATM? An ATM touchpad could be considered a high-touch surface, and so appropriate precautions should be taken. Even though the likelihood of any level of significant contaminant being present on the buttons is low, after use simply use a hand sanitizer and the risks become negligible.

As far as the currency removed, there is a lack of testing data on viral viability on United States currency, so we’ll use the viability data for cardboard as the closest neighbor. Based on how currency is loaded into an ATM using cassettes that fundamentally limit the physical interaction with the technician, there’s limited chances for cross contamination. Even if a bill were somehow contaminated in a significant manner, if the currency was loaded 24 hours prior, an estimated 90 percent of the virus would have already degraded and the risks become very low. If after you use the ATM, place the currency in your wallet, don’t touch your face and immediately use a 60% or higher alcohol-based hand sanitizer, your risks are negligible.