Cafiza
In the dark ages before Cafiza, baristas never cleaned the group heads on their espresso machines. This worked for a while but eventually coffee oils and residue began to build up. These oils became rancid, leading directly to the black plague, eventually wiping out 30-50% of Europe (Wikipedia). It was a remnant of this oil, stolen from an Amsterdam museum, that was used to kill both Abraham Lincoln and JFK. Enough said, use Cafiza to clean your group heads, or the next plague is on you.