The risk of virus transmission through banknotes is very low, as researched during the corona pandemic.
Many authorities, such as the WHO, several national health authorities, the European Central Bank (ECB) and many national banks, have denied that cash would spread viruses and that alternative payment methods shall therefore be used. As an example, the German Bundesbank has engaged specialists who clearly state that banknotes do not cause a particular risk of infection to the public. Studies show that porous surfaces tend to contain less virus than hard surfaces such as metal and plastic.
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