It wasn't clear that it had to be a "fatal" disease. At least that's not the impression I got. Just that it had to be "something." The guy in S. Korea apparently just had a gimped leg and apparently it was enough to protect him.
I'd have to rewatch the mid-part of the WHO area, but pretty sure that's what was called out in the dialog, and then they identified a couple specific bugs by name, although didn't say which one he ended up using.
Only ones i immediately remember were TB and H1N1. Best case, anything not immediately fatal is going to incapacitate you pretty quickly. Which was why they were locked away in the vaults to begin with...
The gimpy leg part I don't get. Unless he had some sort of bad infection he wasn't admitting to? Physical damage isn't going to turn the zombies away, it would smell the same. They aren't taking pity on the guy because he's got a limp, he's got something wrong so the food smells tainted...