New research suggests that SARS-CoV-2, the virus that has enabled COVID-19 to spread across the world, may survive on porous surfaces for up to 28 days.
The study in question concluded that the virus may be more likely to thrive on surfaces in cooler, darker places.
More evidence helps healthcare officials learn about the virus, but many experts believe this data shouldn't cause alarm for those who are washing their hands and already cleaning their homes.
This guide has been medically reviewed by Raj Dasgupta, M.D., a pulmonary and critical care physician and the assistant program director of Internal Medicine at the University of Southern California.
Back in March, not long after the official start of the pandemic, a landmark study published in the New England Journal of Medicine indicated that the novel coronavirus could remain infectious on common surfaces like plastic for up to 72 hours and on cardboard for 24 hours. An April follow-up study published in The Lancet established instances where some surfaces, like stainless steel, could harbor infectious particles for up to a week in the right environment. Since then, health officials have stressed regular cleaning and disinfection of all kinds of surfaces that we touch routinely (inside and out!) to fight SARS-CoV-2, the virus that leads to a COVID-19 diagnosis, as well as regularly cleaning one's hands. Many people have assumed that an object which couldn't be disinfected entirely — like a plush surface or paper — couldn't hold infectious germs after a week at most, but new research is challenging how we interact with these high-touch surfaces as scientists learn more about COVID-19.
A team of researchers at Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO), a national science agency, conducted a study in which they applied SARS-CoV-2 virus particles on even more common surfaces than were previously studied, including glass, stainless steel, and paper money, in a new environment altogether. Their findings suggests that the virus could remain infectious for up to 28 days, much longer than the traditional flu virus and significantly longer than previous evidence postulated. Smooth surfaces, like the glass screens found on our phones, hosted infectious germs at 20 degrees Celsius (around 68°F) for almost four weeks, whereas regular flu germs may only be infectious for a maximum of 17 days.
But the study, published in Virology Journal in early October, is largely different from the two extensive pieces of lab-driven research from earlier in the year. It may well be that this study will only help healthcare professionals understand the virus better in a clinical setting, because officials like Sandra Kesh, M.D., an infectious disease specialist and deputy medical director at Westmed Medical Group, say that people will need to continue to wash hands and clean surfaces as they have before.
"People get very alarmed; the way that [researchers] presented the data, it suggests that the virus can survive much longer, in amounts that's not only detectable, but in amounts that are infectious," Dr. Kesh explains. "But there's a major caveat that I think people need to understand. The laboratory conditions that they perform the study in are not the same as what we experience in the real world."
Below, we've recapped everything that we've learned from leading research thus far, explaining why some experts are cautious about the new study, as well as what you need to focus on as we move into the winter season.
How environment plays a role in cleaning and disinfecting
Scientists are working to establish the length of time SARS-CoV-2 can remain infectious on surfaces, as it's an important piece of information to help people stop the spread of COVID-19 in their communities. But nearly all of the research into the virus thus far has been conducted in a laboratory, which is vastly different from our homes, schools, and offices, including the natural elements in these environments that influence how long the virus can survive on surfaces.
In the Australian study, researchers discovered the 28-day viability period by placing virus particles into a "solution" that they spread across surfaces, Dr. Kesh points out. But the biggest discrepancy between the real world and the laboratory is that the study was conducted in the dark at a controlled temperature with controlled humidity, which isn't a setting for most American families. "As scary as the results are, I don't think there's cause for [added] alarm: The primary mode of transmission remains airborne droplets as well as aerosols, particularly in enclosed environments," Dr. Kesh explains.
Top health officials have established that surfaces most likely become contaminated when an infected individual dispels infectious droplets in the air around the object. And while the scientists behind the new study did use a mucus-like substance to spread the virus onto their test surfaces, Dr. Kesh says that human mucus contains white blood cells, which may influence the virus' susceptibility on a surface differently than a lab-engineered solution.
"The other thing to remember is that the virus is inactivated by UV radiation, Dr. Kesh adds. "Usually, we have sunlight in our homes and have the lights on, too," Officials at the Centers for Disease Control and Prevention have shared evidence indicating that low humidity and colder temperatures are more hospitable for the SARS-CoV-2 virus specifically, "whereas warmer temperature and higher humidity" impacted how long it remains infectious on most surfaces. In homes and other interior spaces, the temps and humidity tend to be less consistent than in laboratories, making a 28-day infectious period significantly less likely overall.
How long does SARS-CoV-2 live on surfaces?
The pandemic research that's been conducted thus far has measured how long the virus can be detected on a surface, but not all studies determined how long the virus remains infectious, which is a key difference. Most experts maintain that the virus doesn't remain viable beyond 24 hours, especially as sunlight and humidity may inactivate virus particles faster. "In my opinion, infectious viruses will only persist for hours in mucus on surfaces rather than days," Ronn Eccles, Ph.D., the former director of the Common Cold Centre at Cardiff University, shared with the BBC in reaction to the study.
Using data collected from the NEJM, Lancet, and Virology Journal, we're outlining how long the virus can be detected on surfaces in a laboratory setting below.
Plastic: Research suggests that SARS-CoV-2 can be detected anywhere from 3 to 7 days, and the latest evidence stipulates that infectious virus may persist up until 28 days on non-porous plastic surfaces.
Metal: On copper, researchers established that viable virus wasn't detected on this particular metal after 4 hours. Other evidence suggests that stainless steel and metals can play host to the virus between 3 and 7 days.
Paper: While the Lancet study determined that SARS could be detected on paper money for up to 4 days after first exposure, money was one surface that successfully held onto the virus in the 28-day range in the Virology Journal findings. The Lancet also determined that virus particles couldn't be detected on printed paper or tissue paper after 3 hours.
Glass: Initial evidence suggested that virus could be detected on surfaces like windows or our screens on televisions, computers, or smartphones for up to 4 days.
Cardboard: Food packaging and shipping boxes were initially subject to debate at the onset of the pandemic, as people disinfected their shopping when they returned home. The NEJM study suggests that viable virus couldn't be detected on cardboard after 24 hours, meaning you might be able to quarantine your shopping outside of the kitchen until then.
Cloth or non-porous surfaces: While evidence has been limited on this category, the CSIRO team's research found that common cotton didn't hold onto the virus beyond two weeks (most of which was inactivated upon first contact).
Some of the research differs on whether a surface remained infectious in a given time period, but at any rate, you should be actively cleaning and disinfecting high-touch surfaces inside your homes guided by the timelines above. Washing your hands properly after returning home is most important, since you can easily bring germs inside your home after being outside and touching all kinds of surfaces.
As more information about the coronavirus pandemic develops, some of the information in this story may have changed since it was last updated. For the most up-to-date information on COVID-19, please visit the online resources provided by the CDC, WHO, and your local public health department.
Should I adapt the way I'm cleaning and disinfecting at home?
As we head into the winter, one thing is clear: We'll need to continue to clean our homes and monitor our hand hygiene moving forward. It seems that all evidence suggests that colder temperatures are more hospitable for SARS-CoV-2 on surfaces as compared to warmer months. But the good news? Many have already established a cleaning schedule for our homes and are paying attention to the hand hygiene of our entire household.
Some of the foremost experts in the health and sanitation industries convened at Good Housekeeping's annual Discover Cleaning Summit to discuss how frequently Americans should be cleaning at home. While much of the focus on home cleaning prior to the pandemic has centered around the toilet, many are now focusing on high-touch points in the kitchen and living room, says Liz Scott, Ph.D., a professor at Simmons University and an infection control consultant for brands within the cleaning industry. Particularly, people are (and should be!) paying more attention to disinfecting surfaces properly in the kitchen and living room: "The high risk areas are firstly our hands, and then secondly, the hand-contact surfaces that we touch," she shared at the Summit. "We have to focus our efforts on surfaces that are high risk of where we might become infected, because there are pathogens there that can be transmitted to us."
The latest research on how long SARS-CoV-2 can live on surfaces shouldn't leave you itching to disinfect each and every surface in your home every day. Rather, Dr. Scott says you should feel good about cleaning, or taking the time to disinfect, the kitchen counter, fridges and sinks, dining tables, coffee tables, and things like doorknobs, handles, and latches on a set schedule. If someone who doesn't live in your home has spent time in an inside space recently, or if someone in your home has become ill, that's a smart time to disinfect a surface, as it can help lower the risk of contracting COVID-19 through high-touch surfaces.
If you're looking for the easiest ways to keep your surfaces clean, the Good Housekeeping Home Appliances & Cleaning Products Lab has the latest on the best disinfectants to use at home. Plus, Director Carolyn Forté walks you through the correct way to disinfect any surface in your home, and shares a quick DIY disinfectant formula for when you need it, below.
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