- The coronavirus is primarily a respiratory illness, and it typically spreads via airborne droplets from an infected person's coughs or sneezes.
- Viral particles can survive for a time on surfaces, but the coronavirus' lifespan on surfaces depends on various factors like temperature and humidity.
- New research suggests the coronavirus can last between three hours and three days on surfaces, depending on the material.
- Here are some best practices for disinfecting surfaces.
- For more stories go to www.BusinessInsider.co.za.
The new coronavirus is a respiratory illness, which means it typically spreads via airborne droplets. When an infected person coughs or sneezes, droplets carrying viral particles can land on someone else's nose or mouth or get inhaled.
But a person can sometimes get the coronavirus if they touch a surface or object that has viral particles on it and then touch their mouth, nose, or eyes. The lifespan of the virus on a surface - a subway pole, a stairwell banister, or even money - depends on many factors, including the surrounding temperature, humidity, and type of surface.
But the rough range is "likely hours to a day or so," Rachel Graham, an epidemiologist at the University of North Carolina, told Business Insider.
A new study from researchers at the National Institutes of Health (NIH), supports Graham's assessment. The study, published today in the New England Journal of Medicine, suggests the virus can live up to four hours on copper, up to a day on cardboard, and up to three days on plastic and stainless steel.
The coronavirus can also live in the air for up to three hours, the study authors found.
How long the coronavirus could survive on surfaces
The NIH researchers compared the new coronavirus' lifespan on surfaces to that of the SARS coronavirus. They found that both coronaviruses lived the longest on stainless steel and polypropylene, a type of plastic used in everything from toys to car parts. Both viruses lasted up to three days on plastic, and the new coronavirus lasted up to three days on steel.
On cardboard, however, the new coronavirus lasted three times longer than SARS did: 24 hours, compared to eight hours.
"The stability of SARS-CoV-2 in aerosols and on surfaces likely contributes to transmission of the virus in healthcare settings," the NIH study authors wrote. (SARS-CoV-2 is the official scientific name of the virus.)
Another study published March 1 in the Journal of Hospital Infection looked at the lifespans of other coronaviruses found in humans on various surfaces. The SARS coronavirus, at a temperature of 68 degrees Fahrenheit (20 degrees Celsius), lasted for two days on steel, four days on wood and glass, and five days on metal, plastic, and ceramics. (The researchers also found that one strain of SARS lasted up to nine days on a plastic surface at room temperature.)
SARS survived for two to eight hours on aluminum and for less than eight hours on latex.
According to Graham, smooth, nonporous surfaces like doorknobs and tabletops are better at carrying viruses in general. Porous surfaces - like money, hair, and fabric - don't allow viruses to survive as long because the small spaces or holes in them can trap the microbe and prevent its transfer, Graham said.
"Coins will transmit a virus better than cash, but this shouldn't be a huge concern," she said. "Basic rule of thumb should be to consider money dirty anyway, because it is. It goes through too many hands not to be."
- Your smartphone, with all its glass and aluminum, can also carry viral particles.
Graham recommended disinfecting your phone, "particularly if it travels to the bathroom with you."
The surrounding temperature makes a big difference
The Journal of Hospital Infection study also found that spikes in temperature made a difference in the lifespans of coronaviruses. An 18-degree Fahrenheit jump, from 68 degrees to 86 degrees, decreased how long SARS lasted on steel surfaces by at least half.
That's because some coronaviruses, including this new one, have a viral envelope: a fat layer that protects viral particles when traveling from person to person in the air. That sheath can dry out, however, killing the virus. So higher humidity, moderate temperatures, low wind, and a solid surface are all good for a coronavirus' survival, Graham said.
This also explains why respiratory viruses are typically seasonal: Cooler temperatures help harden the protective gel-like coating that surrounds the particles.
How to disinfect surfaces
The authors of the Journal of Hospital Infection study noted that human coronaviruses could be "efficiently inactivated" on surfaces within one minute if they're cleaned with solutions containing 62% to 71% ethanol alcohol, 0.5% hydrogen peroxide, or 0.1% sodium hypochlorite.
"We expect a similar effect against the SARS-CoV-2," they added.
Graham said these surface disinfectants could even work within 15 seconds.
"To get the kill rates advertised on the packaging, though, that usually involves waiting for several minutes - between five minutes and six minutes," she added, though that duration is probably essential only if you're cleaning a surface in an area where someone's infected.
Graham said the important thing when disinfecting a surface is getting the potential infectious dose of the virus below a level that will cause disease.
"Most commercial products labeled 'disinfectants' talk about a 99.9% kill rate," she said - that should bring the dose below the threshold that would make people ill. But alcohol-based hand sanitiser is not ideal for disinfecting hard surfaces because the alcohol content is not high enough.
Hand sanitiser is meant to lower how much of the infection is on your hands "without stripping your skin of all its oils and moisture," Graham said. "Surface disinfectants - like Lysol, bleach - are better for surfaces."
Stop touching your face, and wash your hands
Graham emphasised the importance of washing your hands and not touching your face - those are the best ways to minimise your chance of picking up the coronavirus from surfaces.
The recent study concluded that if a person spent five seconds touching a surface where the influenza A virus lives, 32% of the virus living on that surface could transfer to their hands.
"If you're about to eat, fix your makeup, play with the baby, etc., wash your hands," she said.
She also suggested washing your hair if it gets sneezed on, even though the virus doesn't last very long on it.
Of course, the coronavirus can't infect you through your hands, so if you never touch your eyes, nose, mouth, you can avoid infection.
But that's easier said than done.
"Most humans touch their faces several hundreds of times per day, so it's still best to be aware of how clean your hands are," Graham said.
For more information direct from the source, see also:
- the National Institute for Communicable Disease (NICD)
- the latest statements issued by the national government
- the Twitter stream of health minister Dr Zweli Mkhize
- the World Health Organisation's Covic-19 outbreak page
the NICD hotline for Covid-19 is: 0800-029-999.
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