βAn analysis of 22 earlier studies of similar coronaviruses, including Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS) published online this month in the Journal of Hospital Infection, concluded that human coronaviruses can remain infectious on inanimate surfaces for up to nine days at room temperature.β
It's a half-life thing. The larger your initial sample, the longer the sample can go and still have enough infectious ability left.
Scenario: Infected person sneezes over a large area and deposits over a wide area. Then you come by 6 hours later and touch a deposited surface and then 10 minutes later touch your eyes.
Each transition only picked up a fraction of what was left.
And each time period left only a fraction of what was there.
More important to limit travel, limit direct/close contact and clean commonly used surfaces frequently.
And better to avoid replicating the environmental conditions that created the "up to 9 day" figure: low temperatures and low humidity.
Even a day is a long period of time in optimal conditions, and not many situations are close to optimal.