The Covid-19 virus can last for days on many surfaces, according to a new analysis helping to explain its high infectivity.
US researchers found it survives in aerosols for up to three hours, on copper for four hours, up to 24 hours on cardboard and up to two to three days on plastic and stainless steel.
Although the virus has high durability, the researchers say it is about the same as the original SARS virus. This leads to speculation that the additional cause of its high transmissibility is the lack of recognisable symptoms in many of those carrying it.
There is "emerging" evidence to support this, according to the research published in the New England Journal of Medicine and undertaken by US government researchers alongside Princeton University, USA.
The researchers warn: "The stability of SARS-CoV-2 in aerosols and on surfaces likely contributes to transmission of the virus in healthcare settings."
A second piece of genetic research, published last night, rejects conspiracy theories that the virus was human engineered.
Reporting in Nature Medicine, the researchers from the USA and Australia say it is possible that the virus has mutated after reaching humans.
Researcher Dr Kristian Andersen, from Scripps Research, USA, said: "By comparing the available genome sequence data for known coronavirus strains, we can firmly determine that SARS-CoV-2 originated through natural processes."
The researchers found the virus had undergone natural evolution recently, leading to a spike protein so effective at binding to human cells it could not have been engineered by humans.
The virus most closely resembles viruses found in bats and pangolins, they say, adding that it probably evolved to its present state in its animal hosts.
Dr Josie Golding, from the Wellcome Trust, UK, said the findings are "crucially important to bring an evidence-based view to the rumours that have been circulating about the origins of the virus (SARS-CoV-2) causing COVID-19.
"They conclude that the virus is the product of natural evolution, ending any speculation about deliberate genetic engineering."
Nature Medicine 17 March 2020
N. van Doremalen, et al. Aerosol and surface stability of HCoV-19 (SARS-CoV-2) compared to SARS-CoV-1. New England Journal of Medicine 17 March 2020; doi: 10.1056/NEJMc2004973
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