Measles, the Uncontainable

Enchant target creature. If enchanted creature is blocked, copy all plague auras it has and attach
them to the blocking creature. If enchanted
creature blocks, copy all plague auras it has and
attach them to the attacking creature it is blocking.
Plague- While a player controls a permanent with
a Plague Aura, creature spells they cast enter with
a copy of that plague aura attached to it.