The SARS-CoV-2 virus, which causes COVID-19, becomes almost immediately nonviable if deposited on a cash banknote, according to a study.

The research, published in the journal PLOS ONE, suggests that the use of credit and debit cards over cash as a COVID-19 prevention measure is not advisable. The researchers found that the virus shows greater stability on plastic money cards, with the live virus still being detected 48 hours after initial deposition.

However, no viable virus was detected on either cash or card that was randomly sampled in the study, the researchers said. "Early in the pandemic, we had this massive outcry for businesses to stop using cash; all these businesses just followed this advice and said OK we are credit card only," said study author Richard Robison, a professor at Brigham Young University (BYU) in the US.

"I thought, 'Wait a minute, where are the data to support that?' And there simply wasn't any. We decided to see if it was rational or not, and turns out it was not," Robison said. The researchers rounded up a bunch of USD 1 bills, quarters, pennies and credit cards and inoculated the money with SARS-CoV-2.

The cash, coins and cards were then sampled and tested for virus detection at four-time points afterwards: at 30 minutes, four hours, 24 hours and 48 hours. The researchers found that SARS-CoV-2 was difficult to detect on the dollar bills even just 30 minutes after being placed there. The study finds the virus was reduced by 99.9993 per cent at the 30-minute mark.

The researchers tested again after 24 and 48 hours and found no live virus on the banknotes. In contrast, the virus only reduced 90 per cent on money cards at the 30-minute mark, they said. While this reduction rate increased to 99.6 per cent by four hours, and 99.96 per cent by 24 hours, the live virus was still detectable on the money cards 48 hours later.

The coins performed similarly to the plastic cards, with a strong initial reduction in virus presence, yet still testing positive for the live virus after 24 and 48 hours. Researchers were surprised by the instability of the paper banknotes, which in the US are a blend of 75 per cent cotton and 25 per cent linen.

After putting 1 million viable virus particles on the bills, they could not find any virus at all after 24 hours. The research team also obtained fresh samples of USD 1 cash bills, quarters and pennies from around BYU's campus and local restaurants to test them for the presence of the virus.

Within an hour of obtaining the money, the researchers systematically swabbed the surfaces and edges of the cash or coins with a sterile cotton swab. They also swabbed a collection of money cards and detected no SARS-CoV-2 RNA on the banknotes or the coins and only a low level of the virus on the money cards.

"This pandemic has been infamous for people making decisions with no data," Robison said. "We have these people just saying things and massive numbers of organisations just follow it blindly without any data. It turns out in this case, they went precisely the wrong direction," he added.