Not all viruses present on a given surface will be transferred to hands upon touching that surface. Transfer rate or transfer efficiency is a measure of how easy it is for microorganisms such as viruses to move from a surface or object onto hands. We do not know the exact transfer rate of SARS-CoV-2. However, transfer efficiencies tend to be lower from porous surfaces, like fabric, than from non-porous surfaces, like stainless steel. In a laboratory study which used a virus similar to SARS-CoV-2, roughly 5-20% of the virus was transferred from a hard surface to fingers. In comparison only 0.4% of the virus was transferred from porous surfaces to fingers. But SARS-CoV-2 might not behave like the virus used in this study. Even low transfer efficiencies can result in hand contamination with the virus if the virus exists in high concentrations on a surface.
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