The SARS-CoV-2 coronavirus that causes severe respiratory coronavirus disease (COVID-19) is transmitted through respiratory droplets from an infected person. While these droplets are often spread through the air, by coughing or sneezing, they can also survive on surfaces. Fortunately, there are some simple steps that anyone can take to deactivate or destroy the virus.
A recent study found that, on surfaces like cardboard, it seems able to survive for 24 hours, but it can last up to 72 on plastic. Interestingly, it only seems to survive for four hours on copper. A meta-analysis of studies pertaining to other types of coronavirus (eg SARS and MERS) indicated coronaviruses can technically persist on surfaces for up to nine days in the right conditions.
But don’t douse everything you own in Purell just yet – the good news is that the threat this poses may not actually hold up in the real world:
According to one Johns Hopkins professor of cell biology:
“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. But what’s more important is the amount of the virus that remains. It’s less than 0.1% of the starting virus material. Infection is theoretically possible but unlikely at the levels remaining after a few days. People need to know this.”-Carolyn Machamer, Professor of Cell Biology at Johns Hopkins University
The CDC echos a similar sentiment, saying
“Based on what is currently known about the virus, and about similar coronaviruses that cause SARS and MERS, spread from person-to-person happens most frequently among close contacts (within about 6 feet). This type of transmission occurs via respiratory droplets, but disease transmission via infectious aerosols is currently uncertain. Transmission of SARS-CoV-2 to persons from surfaces contaminated with the virus has not been documented.
Transmission of coronavirus occurs much more commonly through respiratory droplets than through fomites.“
So while the virus can remain viable on surfaces for a significant length of time, lack of known cases that are a result of surface contamination could be good news and suggests we should focus more on social distancing than slathering our groceries with Purell. So if you were doing that before, you can take a deep breath of relief (so long as you are six feet or more from anybody else).
Of course, this doesn’t mean we should neglect good sanitation and disinfection practices. Even if respiratory droplets are the most likely form of transmission, surface disinfection can’t be a bad idea. We are also in such early stages in the game that new, conflicting data could potentially still emerge regarding its viability of transmission via surfaces.
Clean Before You Clean
Like other microbes, coronavirus can find its way into layers of oil and grime on your skin and set up camp. Before you disinfect the surfaces in your home, do an initial cleaning to remove surface accumulation that might undermine the efficacy of your disinfectant. Be sure to use proper protective measures as you undertake this cleaning to avoid inhaling or coming into contact with any potentially infected substances that you stir up and wash your hands afterwards.
Use the Right Products
When you wash your hands with soap and water, the surfactant property of soap allows your skin’s oils to bind with water (something that doesn’t happen with water alone) and lifts it off of your skin to send it down the drain. The result is germ-free hands.
But when a sink and soap isn’t available, cleaning the virus off surfaces other than the skin can be improved by using alcohol-based or ammonia-based products, which sterilize the surface by killing the virus instead of moving it away.
Hand sanitizers may look and smell like complex chemical cocktails. But the ingredient that actually does the work of killing germs is still just simple alcohol. The reason other ingredients are added is primarily to help counteract alcohol’s skin-drying properties.
But just because alcohol is what kills the germs doesn’t mean you can easily make your own. Even 80 proof vodka’s 40% alcohol content, still falls twenty percent short of the officially recommended alcohol content for a hand sanitizer. It turns out some of those germs can hold their liquor.
The CDC recommends at least 60% ethanol or 70% isopropanol concentrations in hand sanitizers based on tests of viruses similar to the 2019 coronavirus. Why not 100%? Because it would dry out and irritate your hands so much that it would likely cause more harm than good.
You can also use EPA-approved disinfecting sprays for surfaces or make your own cleaner by diluting one cup (240mL) of bleach with a gallon of water.
When using bleach, be sure you are taking the right precautions. Bleach can irritate mucus membranes, so too much exposure to them might actually make the body more susceptible to infection. If you use a bleach-based solution on a food preparation surface, such as cutting boards or countertops, rinse it thoroughly before using it. Never mix bleach with ammonia or other household cleaners, avoid inhalation (use lots of ventilation) and make sure you are wearing protective gear like non-porous gloves and eye protection when working with it.
Let Disinfectants Work
Do not wipe off your cleaning agent right after spraying it on. Disinfectants require time to spread across the surface and penetrate the protective outer layer of the virus. Wiping it off too early can undermine its efficacy.
A study published in the Journal of Hospital Infection found that human coronaviruses can be eliminated from most surfaces with between 15 and 60 seconds of cleaning with solutions containing 0.1% sodium hypochlorite, 0.5% hydrogen peroxide, or 62% to 71% ethanol alcohol. If you are cleaning a surface that is known to have come into contact with an infected person, however, the length of cleaning should be five to six minutes.
Clean Key Surfaces: Especially In Public Restrooms
When it comes to contamination, there are two types of surface: High-touch and low-touch. High-touch surfaces include doorknobs, drawer or cabinet pulls, light switches, soap pumps, flush handles, toilet seats, paper towel dispenser handles, etc. The handles on toilet partition doors are especially suspect as they are invariably touched before handwashing occurs.
Low-touch surfaces like walls, cables, and the like still have the potential for contamination and shouldn’t necessarily be ignored. However, their likelihood of transmitting a virus is significantly lower since two separate touches would have to occur in a low-touch area before transfer occurs.
Surfaces onto which a sneeze or cough might deposit the droplets that can carry the virus, including mirrors, walls, floors and countertops. If you have children in your home, make sure to clean any surfaces that are at their height as well as surfaces at a grown-ups’ height, and to clean any items that children use, such as step stools or toys. Remember that children have their own way of engaging with the world around them and that they are likely to touch any surface they come across.
All body towels, washcloths, hand towels and rugs or floor mats should be thoroughly and properly laundered to kill potential viruses. To do this, use detergent and bleach for white loads and peroxide or color-safe bleach for dark loads. Always read and follow the instructions on labels to avoid damaging fabrics. If your washing machine has a sanitize or steam setting that is safe for the fabric you are using, use that to kill the virus. Otherwise, use the hottest possible water setting. Running laundry through the dryer on hot for at least 45 minutes will also help kill the virus.
Protect Yourself as You Clean
While cleaning a surface that might have been contaminated by coronavirus, it is important that you take proper precautions to keep yourself from becoming infected. You also should take care when using cleaners containing bleach, ammonia, or alcohol because those chemicals can release dangerous fumes and cause skin and eye irritation.
Avoid getting the cleaner on your skin or clothing, or in your eyes. Make sure that you are working in a well-ventilated space by opening windows and turning on the bathroom’s exhaust fan. Wear disposable latex or other protective gloves to protect your hands from both the cleaning chemical and the virus, or if you use reusable gloves they should be dedicated only to cleaning and disinfection surfaces of COVID-19 and should be cleaned according to the manufacturer’s instructions after each use.
After you have finished cleaning, be sure to thoroughly wash your hands with soap for 20 seconds, dry them with a paper towel (that you then discard), and then apply a hand sanitizer containing at least 70% alcohol. You may want to use a hand lotion after to restore moisture to your skin. Avoid touching your face, mouth, or eyes after cleaning.
Remember that anyone who has tested positive for COVID-19 or who is displaying symptoms of the disease should use a separate bathroom from the rest of your household if at all possible. The bathroom trash can should be lined with a trash bag that is removed on a daily basis; wear gloves when removing the bathroom trash, do not handle any of the trash in the bag directly, and consult with your local health department about how to properly dispose of the contaminated garbage.