The ins and outs of disinfecting coronavirus

The why, how, and what of wiping households clean of coronavirus.
March 25, 2020

Let’s be honest: we know dirt, grime, and dust when we see it around the household, but if we don’t see it, we generally assume the surface is “clean.” Coronavirus, though, can survive for perhaps three days on plastic and metal, according to a recent study (and 24 hours on cardboard). The eyes can deceive: just because a door handle gleams doesn’t mean it’s not covered with virus.

woman disinfecting coronavirus by wiping down countertops in the kitchen.
With any of the effective products you use for disinfecting coronavirus, it’s important to read the fine print on the container. In particular, how long does it take to kill viruses? Photo: Getty Images.

We’re typically better at cleaning than disinfecting. That must change. Here’s a quick primer on household disinfection, with the caveat that the below assumes that no one in the household has been diagnosed with or is suspected to have COVID-19, the disease this particular coronavirus causes. Such households should follow the more stringent U.S. Centers for Disease Control and Prevention guidelines closely.

General disinfectants

First, coronavirus is what virologists call an enveloped virus – the “envelope” being the fatty sphere in which it harbors its human-cell-corrupting RNA. To kill the virus, tear open the envelope. Plain soap does the trick for disinfecting coronavirus, but that demands sufficient physical agitation– hence the 20-second hand wash.

That works in the household, too, as do other household cleaning products (hat tip to Consumer Reports):

  • Soap and water can clean household surfaces – as long as you really scrub. Think about mashing coronavirus to oblivion – which it richly deserves – as you do.
  • A simple mix of bleach and cold water also works for disinfecting coronavirus: four teaspoons of bleach per quart of water – or, for larger loads, five tablespoons (1/3rd cup) per gallon. With standard Clorox or similar, a five-minute period exposed to those mixtures should kill coronavirus, according to the U.S. Environmental Protection Agency. Given bleach’s harshness on stainless steel and countertops, wipe surfaces down with water after those five minutes. A plastic toy or metal item can be immersed in bleach for 30 seconds to disinfect. Two important caveats: 1) wear gloves, and 2) don’t mix bleach with ammonia as the combination is toxic. Bleach solution should be used within 24 hours as it loses effectiveness with time.
  • A straight 3% hydrogen peroxide solution takes out rhinovirus – which is tougher to kill than coronavirus – in six to eight minutes, and so should be at least as quick in disinfecting coronavirus.

Note that you should clean visibly dirty surfaces with soap and water before disinfecting. Also note that vodka, vinegar, tea tree oil, and other natural products were not given bullets in the above list. Studies have not found compelling evidence that they’re effective.

Specialized disinfectants

There are many specialized disinfectants – 274 of them populate the EPA’s list of products capable of killing coronavirus.

That list is not exhaustive. Among other examples, Member’s Mark (Sam’s Club) and Kirkland (Costco) disinfecting wipes aren’t on it, but should be comparable to their name-brand counterparts. On the other hand, the EPA list is bereft of baby wipes, which are not effective disinfectants, especially in disinfecting coronavirus

person wipes bathroom faucet when disinfecting coronavirus.
We are typically better at cleaning than disinfecting, but the coronavirus needs a little elbow grease to kill. Photo: Getty Images.

With any of the effective products, it’s important to read the fine print on the container. In particular, how long does it take to kill viruses? In the case of Kirkland disinfecting wipes, the package says the wipes disinfect for viruses including coronaviruses in three minutes – that’s as compared to killing “99.9% of bacteria in 15 seconds.” In other words, viruses take 12 times longer to kill. So give it time.

With these and other products, take a look at the labels to understand both proper usage and time of effectiveness. Those three minutes comprise a span known as “contact time” – that is, the amount of time the surface should remain wet with cleaner for the advertised effectiveness to be expected. For most wipes, recommended contact time is between two minutes and five minutes. For dilutable or ready-to-use formulations, it’s more typically three minutes to 10 minutes.

The key here is that you need a good deal of disinfectant, particularly with a wipe, to ensure that it sticks around for five minutes of virus-killing. As with soap, proper disinfecting also involves elbow grease – you want to rub the stuff in, pick up much of the virus, and assume the remnant disinfectant will terminate the rest.

Target selection for disinfecting coronavirus

Now, where should you focus those products in your household?

Per the CDC:

Community members can practice routine cleaning of frequently touched surfaces (for example: tables, doorknobs, light switches, handles, desks, toilets, faucets, sinks) with household cleaners and EPA-registered disinfectants that are appropriate for the surface, following label instructions.

In other words, disinfect things people most frequently have their paws on, so add TV remotes, tablet computers, computer keyboards and mice, and cell phones to that list. How often you disinfect depends on how often a chance for coronavirus transmission presents itself. Why not once a day?

man disinfecting coronavirus in his car
Disinfecting coronavirus shouldn’t just happen in your home. Don’t forget the surfaces you touch in your car. Photo: Getty Images.

More vigilance is required, though, if you’ve been out shopping for food, medicine, or whatever else. In that case, you’ll want to retrace your steps from the moment of interaction with outside surfaces to the moment you washed your hands immediately upon return to the house – which we should all be doing.

For example, let’s say you used the touchscreen at the supermarket’s self-checkout. You then got in the car and drove home. Now imagine having left purple finger- and handprints on anything you touched. You might find purple on your keys, the car door handle, the seatbelt plastic/metal and latch, the steering wheel, the shifter, the turn signal, the climate buttons, the touch screen, and so on. You might find them on the garage remote-control buttons and then the house door handle and the sink knob.

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All of it should be wiped down with cleaner upon return, and with enough liquid left behind to satisfy the product’s contact-time requirements.

It may seem like a leap from wiping down your door handles to life-and-death decisions in intensive care units, but wiping down the house can help break chains of infection and ultimately take pressure off the U.S. health care system as it treats the most serious cases.

About the author

Todd Neff has written hundreds of stories for University of Colorado Hospital and UCHealth. He covered science and the environment for the Daily Camera in Boulder, Colorado, and has taught narrative nonfiction at the University of Colorado, where he was a Ted Scripps Fellowship recipient in Environmental Journalism. He is author of “A Beard Cut Short,” a biography of a remarkable professor; “The Laser That’s Changing the World,” a history of lidar; and “From Jars to the Stars,” a history of Ball Aerospace.