Health & Wellbeing

Coronavirus can survive on banknotes for 28 days, but what does that mean?

Coronavirus can survive on ban...
The study found SARS-CoV-2 can persist on banknotes for up to 28 days
The study found SARS-CoV-2 can persist on banknotes for up to 28 days
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The study found SARS-CoV-2 can persist on banknotes for up to 28 days
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The study found SARS-CoV-2 can persist on banknotes for up to 28 days
A droplet of SARS-CoV-2 in artificial mucous has absorbed into cotton cloth
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A droplet of SARS-CoV-2 in artificial mucous has absorbed into cotton cloth
Droplet of SARS-CoV-2 in artificial mucous on a small section of a paper banknote
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Droplet of SARS-CoV-2 in artificial mucous on a small section of a paper banknote
The research was conducted within Biosecurity Level 4 laboratories at the Australian Centre for Disease Preparedness
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The research was conducted within Biosecurity Level 4 laboratories at the Australian Centre for Disease Preparedness
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A new Australian study measuring the survival rates of SARS-CoV-2 on various surfaces has found the virus may be able to survive up to 28 days on glass, stainless steel and even banknotes. However, experts urge caution over how these results are interpreted as they do not translate to conditions influencing real-world transmission of COVID-19.

The new research, from a team at the Australian Centre for Disease Preparedness (ACDP), focused very specifically on the effect of temperature on the lifespan of SARS-CoV-2, the virus that causes COVID-19. In order to eliminate other variables influencing survival time for the virus, the research was conducted under strictly controlled laboratory conditions.

The virus was suspended in an artificial mucus solution, designed to mimic the composition of body secretions. The experiments were conducted in darkness, to eliminate the damaging effects of ultraviolet light on the virus. And, the environmental humidity was permanently locked at 50 percent for the duration of all the tests.

The virus’ survival rate was then tested on several different surfaces at three different temperatures: 20 °C, 30 °C, 40 °C. The core findings from the study reveal the virus does survive longer at lower temperatures. It also survives longer on non-porous and smooth surfaces such as glass and stainless steel.

“At 20 degrees Celsius, which is about room temperature, we found that the virus was extremely robust, surviving for 28 days on smooth surfaces such as glass found on mobile phone screens and plastic banknotes,” explains Debbie Eagles, an author on the new study and deputy director of ACDP.

The research was conducted within Biosecurity Level 4 laboratories at the Australian Centre for Disease Preparedness
The research was conducted within Biosecurity Level 4 laboratories at the Australian Centre for Disease Preparedness

While the findings are robust and certainly of scientific value, adding to our understanding of this novel coronavirus, the general public's interpretation of media reports on this research are in many cases only focusing on the sensational finding that the virus can live on banknotes and phone screens for a month, without any qualification regarding real-world transmission.

Hassan Vally, an epidemiologist from La Trobe University, stresses the limitations of applying this kind of research finding to real-world public health conditions.

“The fact that the virus can survive for a longer time than previously thought under the conditions of this study, which are not generalizable to the real world, is of limited value in understanding the relative importance of contact with surfaces as a transmission route for the spread of COVID-19,” Vally explains.

Timothy Newsome, an expert in virology from the University of Sydney, backs up Vally’s concern over the value of the research influencing an individual’s own risk perception. He suggests studying virus persistence in isolation does not account for many real-world variables that influence viral transmission risk.

Newsome notes that “infectious dose, the effects of saliva and mucus on longevity, social behaviors, and authentic environmental stressors such as sunlight,” are all relevant when accounting for how transmissible the virus may be in real world conditions.

Droplet of SARS-CoV-2 in artificial mucous on a small section of a paper banknote
Droplet of SARS-CoV-2 in artificial mucous on a small section of a paper banknote

However, Newsome does believe the new study may have some utility, especially in defining what is possible. And understanding possible, albeit potentially uncommon, transmission routes can inform more effective broad public health recommendations.

“The findings that under certain, albeit artificial circumstances (in the dark), the longevity of the virus is greater than previous thought informs contact tracing and risk management,” says Newsome. “For example, fomite [surface] transmission cannot be excluded when transmission between individuals is days apart, particularly in a cold environment lacking sunlight. Defining virus persistence can also inform decontamination procedures.”

The Australian team behind the new research make it clear that the striking 28-day survival time is not necessarily a realistic indication of how the virus behaves in the real world. But, Eagles does affirm the value of the finding as crucial for authorities developing risk mitigation strategies.

“While the precise role of surface transmission, the degree of surface contact and the amount of virus required for infection is yet to be determined, establishing how long this virus remains viable on surfaces is critical for developing risk mitigation strategies in high contact areas,” says Eagles.

A droplet of SARS-CoV-2 in artificial mucous has absorbed into cotton cloth
A droplet of SARS-CoV-2 in artificial mucous has absorbed into cotton cloth

Some experts have suggested the new study is so narrow its results border on irrelevant. Speaking to BBC, Ron Eccles from Cardiff University questions the mucus solution used in the study. He points out human mucus is a complex combination of compounds and suggests it is unlikely the virus would persist for days on surfaces.

"Viruses are spread on surfaces from mucus in coughs and sneezes and dirty fingers and this study did not use fresh human mucus as a vehicle to spread the virus," says Eccles. "Fresh mucus is a hostile environment for viruses as it contains lots of white cells that produce enzymes to destroy viruses and can also contain antibodies and other chemicals to neutralise viruses.”

Faheem Younus, an infectious disease specialist from the University of Maryland, called the new study “nonsense” on Twitter. He suggests the artificial lab conditions used in the experiments are not at all generalizable to the real-world and claims banknotes and cell phones are not a COVID-19 risk. He even joked that those concerned should send him their money and phone if they are still afraid.

Underpinning these concerns regarding the new study’s findings is the growing belief among scientists that the vast majority of COVID-19 cases are due to respiratory transmission and not surface transmission. Nearly a year into this pandemic, cluster case studies suggest surface transmission of the virus is rare.

Monica Gandhi, from UC San Francisco, notes this shift from concerns over surface, or fomite, transmission to more aerosol forms of transmissions is one of the key things we have learned over the past six months.

“There was a lot of fear at the beginning of the pandemic about fomite transmission,” says Gandhi in a recent interview with Nautilus. “We now know the root of the spread is not from touching surfaces and touching your eye. It’s from being close to someone spewing virus from their nose and mouth, without in most cases knowing they are doing so.”

So although this new study offers valuable new insights into how SARS-CoV-2 can survive on surfaces under particular environmental conditions, the findings certainly do not imply there is a high risk for transmission from viral particles sitting dormant for weeks on banknotes or cell phones.

The new study was published in the journal Virology.

Source: CSIRO

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12 comments
guzmanchinky
it means use purell before touching your face or your food. duh.
KaiserPingo
Appart from US and some poor African countries, who uses that kind of oldfashioned money ?
FB36
It means, use credit/debit card for all shopping, instead of cash, as much as possible!
Catweazle
All European countries still use cash, KaiserPingo, if you search for "euro banknotes in circulation" you will find that European Central Bank data shows that in fact the number of euro banknotes in circulation is steadily increasing, from ~€8bn in 2002 to ~€25.5bn today. It seems you need to get out more!
Pablo
First, the study used "plastic" bank notes, ours in the US are still printed on paper. Second, this study will indubitably be used by anti-cash bureaucrats to speed their efforts to get rid of cash in favor of traceable, fully taxable e-transactions. Orwell was a few decades off with 1984, but spot on as far as the new world order.
Bob809
It means that those who want to remove one of the ways lots of people here in the UK want to pay for there stuff, by cash, will be removed, one way or another. Using this tactic will of course scarethose vulnerable in he head people into never using cash again. So the number of cash users will drop and they will say, 'Well, cash usage has dropped, so lets get rid of it.' There are still many elderly people who prefer cash, my own 82 year old mother being one of them. It's just another of breaking down society as we know it.
Rusty Harris
Just means another way to "convince" people to ditch cash. And, once that happens, say bye bye to what little privacy you have left.
Also, ANYTHING you purchase, any money you make will be traced. Makes it easier for the government to TAKE your money in the
form of taxes or, anything else.
Signguy
Pablo: you are correct; THIS IS NOTHING MORE THAN FEARMONGERING!
buzzclick
The reason cold and flu rates go up in winter is because the cold temperatures and humidity do 2 things, the viruses live longer on surfaces and people touch their nose much more often. This certainly applies to the corona virus as well. Entering a public space thru a door, keep that in mind before touching the handle to pull, and push it open with your arm or shoulder. I have been doing this for so long that I do it without thinking. It blows me away that so many people still think you catch a cold or flu because of the cold. The coming winter will be a real test for the fight against SARS-Cov-2.
paul04
instead of wasting time testing cash, should have tested mail, frozen foods etc. cash is almost never sent overseas, but many other things are.