The Viruses are hazards and semi-main antagonists in the 2015 online MMO Agar.io. They appear to be green balls with spiked edges.
The viruses are common hazards found scattered all around the map. Smaller cells can hide in the viruses. However, once the player gets too big, they become extremely harmful, virulent and dangerous, breaking cells that collide with them into smaller pieces, leaving them vulnerable to bigger cells. New viruses can be created by ejecting seven pieces of mass into them, this can be used to destroy bigger cells.
- In some cases, they are actually helpful, smaller players can either hide in them to escape large cells, wait and ambush smaller cells, or feed them seven pieces of their mass, making them split in two, this can be used to break down bigger cells into smaller cells.
- In Experimental Mode 5% of the viruses were a little larger and a bit darker on June 1, 2015, they were removed the next day.
- While the exact number is unknown, there is actually a limit to how many viruses can be on a server at once. If there are too few viruses, they will begin to spawn randomly throughout the map. If there are too many, ejected food will pass right through them so players cannot create new viruses.
- In addition to the common green viruses, there are also red viruses. They are only found in experimental mode and are somewhat rare. They create food and can trap cells inside them and turn them into food for other players.