Games : Minecraft Disease

I am trying to create a "disease" in minecraft. What I am doing is setting an entities score to 1 if they have the disease, then testing if they have that disease, if they do, it would set several other scores for the effects of the disease. Then I tried to make said disease contagious. If, say a zombie is infected by the disease, and I walk near it, it works perfectly fine and I get infected. What doesn't work is if said zombie walks past another mob, the other mob isn't infected. I can't figure out why. Here is the code:/execute @e[score_Death_min=1] ~ ~ ~ /scoreboard players set @e[score_Death=0,r=3,c=100] Death 1 And here is the error message: [12:11:58] Failed to execute '/scoreboard players set @e[score_Death=0,r=3,c=100] Death 1' as Test Subject