The Alien Virus Canister (also known as the "Goo Jar") is a special trash item that can be found only in the level Caduceus. It can be brought to The Office via the Janitor's Trunk, then to another level where it can be broken to earn the Plague Bearer achievement.
The Alien Virus Canister appears as a long glass container filled with a glowing green liquid surrounded by a metal framework.
When dropped or otherwise hit with enough force, the alien virus canister will shatter and spread its contents across the nearest surfaces, including corpses. The resulting puddle of goo is unlike other messes in Viscera Cleanup Detail in that it glows bright green in dark environments. Corpses hit with alien virus canisters become stained with a darker green stain.
According to a document in Caduceus, the virus within the Alien Virus Canister has the ability to transform both living and dead tissue into a kind of 'sponge', feeding off cells, spreading the infection, and ultimately killing any living hosts. The player, however, is immune to its effects, unlike the effect of the alien artifact in Unearthly Excavation.
A variation of the standard Alien Virus Canister can be found within the game files half-filled with clear fluid.