His co-worker he was closely confined with (small plant; small lunch room) has tested positive and is hospitalized. The plant was closed, and some massive sterilization procedure underway.

And of course my son the line Engineer was called in to help close the plant (stop all the machines since the operators were sent home; unload and purge the materials; pickle the storage and computer systems). So his exposure there was 100X everybody else's as he had to visit every machine and every place in the plant.

'potentially infected' (exposed to the virus)

...and spend time confined in there with a dozen other people at a time, breathing the same air and sitting at the same table.

And that was probably it. The language from credible authorities is typically that surface transmission is much less of a factor than breathing in what someone else just breathed out. E.g., "Transmission of coronavirus occurs much more commonly through respiratory droplets than through fomites." (https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-si...)

Sorry for the weasel words, but there's so much the science isn't clear on that they remain necessary.

It might be more to do with eating.