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The Covid-19 virus can remain infectious on surfaces like banknotes and smartphone screens for much longer than previously thought, up to 28 days, researchers at the National Science Agency of Australia (CSIRO) have found. However, some experts questioned whether viruses remaining on surfaces pose a real threat of infection. Most often, coronavirus is transmitted by airborne droplets when sneezing, coughing or talking.
At the same time, Australian scientists conducted experiments in the dark, and meanwhile, it is known that ultraviolet light kills viruses.
In the course of previous laboratory studies, it has already been established that SARS-Cov-2 can persist on banknotes and glass surfaces for up to two to three days, and on plastic and steel – up to six.
But now scientists from CSIRO have found that coronavirus is much more tenacious, and at room temperature can live on smooth surfaces such as plastic and paper banknotes and glass smartphone screens for up to four weeks. A common influenza virus, by comparison, survives up to 17 days under the same conditions.
“By figuring out how long a virus actually remains viable on surfaces, we can more accurately predict and contain its spread and better protect populations,” said CSIRO Executive Director Dr. Larry Marshall.
However, former director of the Center for the Study of the Common Cold at the University of Cardiff, Professor Ron Eccles, criticized the work of the Australians, saying that the assumption that the virus can live on the surface for 28 days “instills unwarranted fear in people.”
“Viruses get to surfaces from dirty fingers and droplets of mucus when coughing and sneezing, and this study did not consider fresh mucus as a mechanism for spreading the virus,” explains Professor Eccles. – Meanwhile, such fresh mucus serves as a hostile environment for viruses, since it contains many white cells that produce enzymes that destroy viruses, and may also contain antibodies and other elements that neutralize these viruses. Therefore, from my point of view, infectious viruses contained in mucus on surfaces can live for hours, but not days. ” …
And the professor of medicine at the University of California Monica Gandhi last week did stated in an interview with Nautilus magazinethat the coronavirus is not transmitted through surfaces. “At the beginning of the pandemic, many feared secondary transmission, but now we know that the reason for the spread is not that you touch surfaces and your eyes, but that you are close to the carrier of the viruses, from which they fly out of the nose and mouth. , although they themselves, as a rule, do not even know about it, “explained Professor Gandhi.
Wash your hands often, but so do your smartphone screens
Covid-19 spreads mainly through airborne droplets. Scientists have already found that infection in this way is possible within more than three hours after the virus enters the air. Much less was known about the ability of viruses on surfaces to remain infectious.
In particular, the assessment of the virus survival on steel surfaces gave a very wide range of results: from 3 to 14 days at room temperature.
The authors of the new study wanted to find out how long the virus remains viable on glass, paper and plastic banknotes and steel. They found that it lives much longer at room temperature than previously thought.
In this case, the experiments were carried out under conditions favorable to the survival of the virus – in the dark and at constant humidity and temperature, which practically does not happen in real life. When the temperature was raised to 40 degrees, the viruses did not survive for a day. In addition, viruses felt better on a flat, smooth surface, and on the tissues, for example, after 14 days, not a trace of them remained.
Be that as it may, experts point out that no one has canceled the golden rule of constant hand washing, but to this we must add the need to wipe the screens of smartphones more often.
At the same time, scientists have found a connection between the trend of SARS-Cov-2 to survive better on steel surfaces at low temperatures and outbreaks of Covid-19 in meat factories and refrigerated storage facilities around the world.
CSIRO researchers also emphasize that based on their experiments, it can be concluded that viruses are able to persist on fresh and frozen food.