How long does SARS-Cov-2 survive on surfaces?

 A study published in New England Journal of Medicine looked at the viability of the virus on surfaces.  The reduction of number of surfaces are measured in log numbers. Therefore we look at 10 fold reduction of viral agents. Say for example you have 100,000 viruses, then we would want to know how long it takes for enough viruses to die to reach 10,000.  In order for the virus to be almost extinct , it must be reduced by a 100 fold.  Therefore that original 100,000 viruses would reach 100.

In the case of SARS-COV-2, results from the NEJM are shown, survival of the virus at room temperature drops 10 fold for each 8 hours on cardboard,  12 hours on steel or 24 hours on plastic.  To have 100 fold drop then you have to double these times.   A single cough from a n infectious person generates 3500 infectious virions. Starting from this amount, the number of infectious viruses become undetectable at 2 days  on cardboard and steel and 4 days on plastic. This indicates that we should clean cardboard and plastic or wait a few days before handling them.