He isn't even sick.
Yeah, there’s that little detail too. And he has been not sick for a long, long time, all the while carrying this bug that’s settled in enough to cause an X-ray-visible lesion on his lung. Where is the panic about all the people he was in close quarters with over all that time (which may well be measured in years, since TB progresses much more slowly in otherwise healthy individuals)? Heck, during at least a few patches of that time, he probably had garden variety bronchitis or post-nasal drip that caused him to cough, thus actually raising his transmission potential somewhat above the lightning-strike-on-a-sunny-day level.
He is extremely sick...but asymptomatic at this point. That makes him even more dangerous because when he’s feeling fine, he’s less likely to take precautions.