Mortality is taken over the population as a whole. You want the case fatality rate (probability of death if you're infected), which in the US is 7-9%. Globally, some countries have TB case rates >30%.

TB is a very ancient, very scary disease that's co-evolved with us. It's not much of an exaggeration to say that large parts of modern medicine were invented specifically to get a handle on TB because it has historically ravaged entire populations when left untreated.

Now, now, sick people have smaller appetites and don't eat as many eggs.

No you're missing the subtext entirely. They're making a joke and it's about bird flu not TB.

I presume that the chickens are being killed due to fear of bird flu.