For countless generations our biochemical system adapted to increasing our chances of survival and reproduction, not our happiness. The biochemical system rewards actions conductive to survival and reproduction with pleasant sensations. But these are only an ephemeral sales gimmick. We struggle to get food and mate in order to avoid unpleasant sensations of hunger and to enjoy pleasing tastes and blissful orgasms. But nice tastes and blissful orgasms don't last very long, and if we want to feel them again we have to go out looking for more food and mates.
In the Stone Age, the average human had at his or her disposal about 4,000 calories of energy per day. This included not only food, but also the energy invested in preparing tools, clothing, art and campfires. Today Americans use on average 228.000 calories of energy per person per day, to feed not only their stomachs but also their cars, computers, refrigerators and televisions.
The physicist Max Planck famously said that science advances one funeral at a time. He meant that only when one generation passes away do new theories have a chance to root out old ones.
It is therefore likely that major epidemics will continue to endanger the humankind in the future only if humankind itself creates them, in the service of some ruthless idology.