Referencing NYT article published 18 March, updated 18 April 2020:
The coronavirus can live for three days on some surfaces, like plastic and steel, new research suggests.
The length of time that the new coronavirus is found to survive on cardboard is about 24 hours, which suggests packages that arrive in the mail should have only low levels of the virus — unless the delivery person has coughed or sneezed on it or has handled it with contaminated hands.
The virus lives longest on plastic and steel, surviving for up to 72 hours. But the amount of viable virus decreases sharply over this time. It also does poorly on copper, surviving four hours.
Dr. Linsey Marr, who is an expert in the transmission of viruses by aerosol at Virginia Tech in Blacksburg, said based on physics, an aerosol released at a height of about six feet would fall to the ground after 34 minutes.