I don't think this is very likely. Mortality runs counterproductive to spreadability for diseases, and the human population is so massive and diverse at this point.
If we want to get serious, if humanity suffers an apocalypse it will most likely be from a combination of things. Even if it's chiefly climate change, that problem isn't distinct from global conflict (war) or even disease.
50% of us die from being baked by the sun
20% die in floods
10% die from disease
5% die from war
0.000000000001% die from a Republican Muslim suicide bomber that allahu akbars our fantasy leagues because we tread on his whatever amendment rights for some reason