Where did it say they're a food employee? Also, if it's, like, the flu, a lot of food employees still go into work because they only get paid half of minimum wage and, basically, live on their tips and they can't afford to miss out on those. If you're a food employee and have thrown up or had diarrhea multiple times in the past couple of days, you can't come to work without having shown no symptoms for, at least, 2 or 3 days and you need a clean bill of health from a doctor and I think that's what you're thinking off.

I was just assuming since he said he picked up an extra hour shift

Regardless of whether it was a food service job, you are putting your coworkers at risk by coming into work sick.

There are countless other jobs where people work in shifts that people could end up with an extra hour that also don't involve food; retail, for example.

As well as your employers' expectations of you.