Virus fragments. The ability of the virus to infect decreases quickly.

Honestly curious, do you by chance have a source for this ability to infect decreasing quickly? I would love to share it becasue many people are getting paranoid about how long a tabletop or doorknob could infect them after being touched.

That doesn't mean much without also accounting for how easily an infected person actually spreads the virus into their environment, as well as how likely copies of the virus left in the environment are to actually infect someone.

I would suspect that as long as people don't sneeze/cough without a tissue they are not actually spreading that much copies of the virus on surfaces. And similarly I would also expect that if you wash your hands before eating or touching your face, you are not that likely to get infected even if you had touched a surface with viral particles on it.

But of course I have no evidence for any of this since the studies have clearly not been done yet.