It currently just doesn't work. Ideally a new version doesn't damage the entity, but marks the player as an attacker anyway. It should probably also constantly alert all the other entities of the same time nearby.
Ideally a weakness + slowness effect gets constantly applied for the whole duration, which should be extended for NPCs.
Players should be treated separatedly, with an constantly reapplying effect, until their blood gets back to normal levels. Low blood on players should also cause mild hunger, and blood should only regenerate when the food level and saturation are over a threshold.