If (and I repeat *if*) his last day of work was the 10th, and if he wasn't visibly symptomatic on that day, that would mean that either Alcon was imparting that they didn't notice symptoms while he was at work on the 10th, or someone else told them he wasn't symptomatic when he was admitted on the 12th.
Or it could mean that they simply took a leap of logic and deduced that because he wasn't symptomatic on the 10th, that he still wasn't symptomatic on the 12th, the day he was admitted.
Am I making any sense?
I don't know if you are making sense. I believe you have taken on a job well above your pay grade.
This is a task better suited to the Ebola Czar.