The Virus

Effects

Inflicts poison on enemies who make contact with Isaac.
- (Removed in Afterbirth) The poison deals 2 damage per tick (3 damage per second) and lasts for 2-3 ticks.
- (Added in Afterbirth / Removed in Afterbirth †) The poison deals Isaac's damage per tick (1.5x Isaac's damage per second) and lasts for 2-3 ticks.
- (Added in Afterbirth † / Removed in Repentance) The poison deals Isaac's damage per tick (1.5x Isaac's damage per second) and lasts for 6 ticks for normal enemies and 3 ticks for bosses.
- (Added in Repentance) The poison lasts for 6-7 ticks and deals damage equal to (0.2*HeartContainers^2) + 2, where HeartContainers is the total number of heart containers and bone hearts Isaac has.
  - The poison can be continuously applied to bosses, which normally are immune to status effects for a brief time after being inflicted with one.
(Added in Repentance) Lets Isaac deal 24 contact damage per tick on top of applying poison (48 damage per second).
(Added in Afterbirth / Removed in Repentance) Enemies who are killed after they have been inflicted with this type of poison have a 20% chance to drop Black Hearts.
(Removed in Repentance) -0.1 speed down.
- (Removed in Afterbirth) This is not applied until the next time Isaac's speed stat is updated.
(Added in Repentance) +0.2 speed up.
(Added in Afterbirth) This item belongs to the Spun set. Collecting three items from this set will transform Isaac into a buff berserker.

(Added in Afterbirth / Removed in Repentance) The black heart is only dropped if the poison was caused by The Virus. The item's effect doesn't extend to poison tears.
(Added in Afterbirth / Removed in Repentance) If an enemy doesn't do contact damage, The Virus can safely be applied to it for more chances at black hearts. Black flies, Mulligans, and Hosts are the most common enemies this can be applied to.
- (Added in Afterbirth / Removed in Repentance) With Skatole, Hives and Swarmers will constantly spawn normal Flies, meaning they can be endless sources of Black Hearts.
- (Removed in Afterbirth †) Although Stonies and Shopkeepers can't be visibly poisoned, they still can drop Black Hearts if destroyed after being touched.
Enemies won't start taking poison damage if they are pushing up against Isaac; The Virus will be constantly trying to apply poison and refreshing the ticks where poison damage would occur.
- (Added in Afterbirth / Removed in Repentance) Gnawed Leaf and The Virus can still work if Isaac has a short-range orbital such as Cube of Meat or Ball of Bandages, as it will kill enemies pushing against Isaac that are not taking poison damage while still dropping Black Hearts.

(Removed in Repentance) Odd Mushroom: The speed down from the Virus does not stack with the Odd Mushroom; if both are collected, only a total of -0.1 applies.