Coronavirus Traces Found on Bleached Surface After 8 Days, as Study Finds It Can Live on Skin for 9 Hours

Fragments of the coronavirus that are no longer infectious can linger on surfaces wiped down with bleach for as long as eight days. That's according to the authors of a study, who say their work could help with checking if objects are carrying the germ.

The study, published in the journal mSystems, comes as scientists work to gain a deeper understanding of the coronavirus that causes COVID-19, which was first reported in China in late 2019 and has since infected at least 36.2 million people worldwide. Over the weekend, a separate team of researchers published a study in the journal Clinical Infectious Diseases that suggested the virus can stay stable on human skin for up to nine hours.

Evidence suggests the coronavirus can stay active on surfaces for days and go on to infect people. So the authors of the mSystems paper wanted to assess how well methods to collect samples of the virus from surfaces found in buildings work. This research could one day help ensure buildings are properly cleaned and virus-free, they said.

In their research, the team used a virus that was not infectious and couldn't replicate as a stand-in for the coronavirus to contaminate different surfaces. The seven surfaces used in the study included bare stainless steel, stainless steel painted with white acrylic paint, a plastic known as PETG, and fiber-reinforced plastics that are sometimes used to create office walls.

The team collected some 368 samples from the surfaces they contaminated, and measured how easy it was to recover the virus. Eight days after the objects were dosed with the virus, the surfaces were wiped down with bleach and sampled again.

"In some cases, noninfectious viral fragments of SARS-CoV-2 persisted on surfaces for as long as 8 days even after bleach treatment," the authors wrote.

Although there were viral fragments on the surfaces, the samples tested negative. This suggested the surfaces weren't carrying the virus, or were at levels too low to be picked up by equipment, according to the team.

The authors gave the example of the Diamond Princess cruise ship, home to a COVID-19 outbreak in the spring, where fragments of virus were found after it was with cleaned bleach. The "surprising" results and other apparent false-positives can likely be explained by the method used to test the samples, they said.

The skin study

To conduct the study published in the journal Clinical Infectious Diseases, scientists took human skin samples from autopsies. They swiped these with the coronavirus, as well as a strain of the flu.

The coronavirus was found to survive on the skin longer than the flu, at approximately 9 hours versus 1.8 hours.

"These results indicate that SARS-CoV-2 has a markedly higher stability on human skin than that of IAV [flu]," the team wrote. This finding was important for preventing the spread of the virus.

Both viruses were "completely inactivated" 15 seconds after being treated with 80 percent ethanol, the alcohol used in hand sanitizer. The team acknowledged their study was limited because they used one type of the coronavirus and the flu, and three skin samples were used.

Ian Jones, a professor of virology at the U.K.'s University of Reading who did not work on either paper, told Newsweek: "Studies of virus inactivation on surfaces are a necessary part of the overall picture of SARS-CoV-2 [the coronavirus] but it is always difficult to know how accurately model studies reflect real world situations, temperature, rubbing hands on clothing, how much hand to hand contact there is and so on.

"Rather than getting hung up on scraps of virus remaining for this and that time it is best to use these studies to reinforce the need to wash hands regularly as part of COVID awareness measures."

scientist, lab, stock
A stock image shows a scientist at work. Scientists are trying to understand how long the coronavirus that causes COVID-19 can remain active on certain surfaces.