Today, we look at the transmission of the coronavirus – and ask – ‘How long can the SARS-CoV-2 coronavirus survive on surfaces like paper?’
The best way to survive COVID-19 is not to get it in the first place. Governments can only do so much. Preliminary evidence from Japan suggests the cancellation of events, gatherings, and meetings may slow the spread of COVID-19 by as much as 35 percent, but that has not been enough to contain the outbreak. During the unbridled phase of a pandemic, the best thing we can do is shelter in place, staying home to reduce contact with those outside our households as much as possible. It’s something nonessential workers can all do. Put simply, in the American Journal of Emergency Medicine: “Staying home saves lives.” This is how social distancing works. Instead of a scenario like this…you start breaking some of these exponential chains of transmission. So, one person staying home can have a huge effect.
And you can’t just wait until you hear it’s in your area. I grew up in Wyoming, which months in only had a few hundred confirmed cases in the whole state. But by the time a single death occurs in your community, hundreds or even thousands of cases are likely present. We just haven’t done the testing; so, unless you’re on some remote desert island somewhere—a remote desert island with good internet if you’re watching this—then you should just assume the virus is in your neighborhood, wherever you live.
Those of us who need to leave our homes to provide essential services, from direct care to food delivery, should strive to keep a safe distance from others, and sufficiently sanitize our hands every time we touch a public surface before we touch our mucous membranes––meaning our eyes, or the inside of our nose or mouth. This is good social distancing. This? Not so much. Once the pandemic is more under control, ample testing is in place, and the healthcare system is no longer overrun, these social distancing precautions may start to be relaxed, at least for less vulnerable individuals.
The good news is you can’t infect others if you’re not infected yourself, and you can’t get the virus unless the virus can get to you. The COVID-19 coronavirus is thought to be transmitted from one person to the next via respiratory droplets coughed out by the infected, propelled through the air, and then landing up the nose, in the mouth, or perhaps even on the eyes of a person nearby. As a sign in 1918 put it, “SPIT SPREADS DEATH.” Indirect avenues of spread involve infecting yourself by touching your eyes, nose, or mouth with hands contaminated by a virus-laden object or surface, such as rubbing your eyes, or picking your nose after shaking someone’s hand, or touching a public surface like an elevator button, handrail, gas pump, or toilet handle. The levels of virus swarming in the snot of COVID-19 sufferers can reach close to a million per drop, which explains how easy it is for them to so thoroughly contaminate their surrounding environment.
The presence of the COVID-19 coronavirus in stool samples for up to weeks after infection— in fact, sometimes you can have a negative throat swab, but a positive anal swab––suggests…another way toilets may potentially transmit infection. As you may remember from my why-you-need-to-disinfect-your-toothbrush-with-white-vinegar video, modern flush toilets aerosolize a plume of up to 145,000 droplets of toilet water into the air, which can remain floating around for at least thirty minutes. This may be one of the ways poliovirus is transmitted…. So, “Put a lid on it.” Close the lid before you flush and then, of course, thoroughly wash your hands.
The presence of the coronavirus in feces is also why the Oregon State health authority recommended people press pause on their peach emoji, and why the New York Post asked if coronavirus could be spread through farts, suggesting flatulence may be an aerosol-generating procedure, something I was surprised to see was actually put to the test. “It all started with an enquiry from a nurse.” She wanted to know if she was contaminating the sterile environment of the operating room. Investigators were determined to find out. A colleague was asked to toot onto two petri dishes, either fully clothed or with trousers down. And…only the bare-bottom fart sprouted bacteria, suggesting that clothing acts as a filter. Pants are like a mask for your butt; both for the gut bacteria and the splatter ring they found of skin bacteria thought to be blown from the cheeks by the sheer velocity of it all. Their final conclusion? “Don’t fart naked near food,” or at least within two inches of food. Similar advice was given in the New York Post piece, advising people to throw caution to the…wind. A whole ’nother meaning to silent but deadly.
Coughed virus… may make it more than 2 inches, though, which is why it’s safer to get groceries delivered than to go shopping yourself…. During the SARS outbreak, traces of the virus were not only found on items handled directly by patients (like TV remote controls), and surfaces touched by those who interacted with the patients (like a refrigerator door at a nurses’ station), but also floating in air samples taken from an infected patient’s hospital room, suggesting the possibility of more robust airborne transmission than just coughed droplets. A similar study performed in a COVID-19 patient’s hospital room found the virus on the majority of sampled surfaces, but all of the air samples were negative. Since then, though, we’ve learned differently. Studies performed at the Nebraska Biocontainment Unit and the National Quarantine Unit found the majority of air samples tested positive for traces of the virus—even in the hallways outside of patients’ rooms. However, the researchers were unable to verify if the airborne virus was infectious, given the extremely low concentration: less than a hundred copies per cubic foot of air. Nevertheless, because we know the virus can remain viable for hours when experimentally misted into the air, special care should certainly be taken by healthcare workers during aerosol-generating medical procedures.
How long does the virus last on contaminated surfaces? You may have heard that coronaviruses, like flu viruses, are “enveloped” viruses. Enveloped in what? As coronaviruses, shown here in yellow, bud out of infected cells, shown here in blue, they cloak themselves in the outer layer of our cells. They’re wrapped in a stolen swath of our own cell membranes. That oily coating helps them hide from immune surveillance because it looks like us, but it also makes them susceptible to disinfection and environmental inactivation. Non-enveloped viruses, like polio, can last for weeks outside of the body, whereas enveloped viruses tend to only be able to survive for days. As enveloped viruses go, though, coronaviruses tend to be relatively resistant.
There’s a coronavirus that infects pigs, for example, that can last for a month on nonporous surfaces like metal, plastic, or glass, but, at most, human coronaviruses only make it about a week. On copper and brass, coronaviruses may not be able to survive more than a few minutes at low levels of contamination, and a few hours at higher doses. But different coronaviruses have different environmental stability. The SARS coronavirus lasted more than six days dried on plastic, whereas one of the common cold coronaviruses didn’t even make it three days. The SARS virus… lasts up to four days in water or soil, but survived for just minutes after drying on paper when lightly soiled, or up to a day when heavily contaminated, and less than an hour on cotton cloth. But what about SARS 2, the coronavirus that causes COVID-19?
The COVID-19 virus appears to be more stable on paper than the SARS virus, with infectivity extinguished only after twenty-four hours at the same viral load that led SARS to become inactive after eight hours. The half-life of the COVID-19 virus on steel or plastic is about six hours; so, about 99 percent is gone by forty-eight hours, but it may take as long as 96 hours for all infectivity to disappear.
On cloth, the COVID-19 virus may only last for one day, but on the outer layer of surgical masks, it can survive for at least a full week. On printing paper, though, the COVID-19 virus appears to survive for less than three hours.
The virus can only infect you, however, if it can get inside you. Having the virus on your fingers is only a problem if you then inoculate yourself by transferring that virus to your eyes, nose, or mouth. It’s funny when they do experiments for like the common cold to see if transmission is more through the air or through touch; they put people in these crazy arm braces where they can’t bend their elbow, ensuring that they never touch their face.
Having the virus on your fingers is only a problem if you then inoculate yourself by transferring that virus to your eyes, nose, or mouth. It’s not your face in general—touching your forehead, cheek, or chin is presumably no more dangerous than touching your elbow. The virus can’t pass through your skin. The virus can only replicate in live cells, and the outer layer of your skin is covered by protective strata of dead skin cells. To get into your lungs, the virus has to find its way to your mucous membranes, the moist lining of your eyes, nostrils, or mouth. (The reason your nose starts to run when you cry is that tears drain through tiny channels that tunnel through the nasal bone and spill into your nostrils, and viruses in your eye can travel the same route to get to your lungs).
As long as you don’t touch your face, why does it matter if surfaces are contaminated? Because you do touch your face. The oft-repeated twenty-three-times-an-hour statistic is an overestimate, since, of the touches recorded in the cited study on university students, most were just to the skin on the face, but ten touches an hour were to the eyes, nose, or mouth. Adults videotaped in an office-type setting did worse, each touching their nostrils, eyes, or lips an average of nearly sixteen times an hour.
What about doctors? Medical professionals were covertly observed during a grand rounds lecture at a hospital. And… about one out of every three subjects picked their nose at least once.
In family medicine offices, clinicians and staff touched their eyes, nose, or mouth an average of nineteen times in two hours (with a range from 0 to over 100 touches). More concerning in terms of patient safety, however, was the finding that doctors only wash their hands about 30 percent of the times they should—even in intensive care units. And, even when they did manage to wash their hands, it was for an average of less than nine seconds.