You've underestimated the reach of the Is-Ought problem. Again, we can't say "humans sometimes practice empathy therefore humans should practice empathy". You, like Sam Harris, start by ignoring the Is-Ought problem and proceed with an assumption "sickness"/pain/suffering is The Objective Negative Standard (says who?) which falls far short of approaching a refutation of Hume's observation. Here is his observation: there is a gap between Facts (that which Is--like "sickness") and Values (moral commands--that which we Ought to do) and this fundamental difference remains.