The Anti-Team Penalty is a mechanic that is meant to make teamers lose mass. However, it can also accidentally affect solo players. Knowing how to avoid it is a skill in itself, both for teams and solo players.
The Anti-team penalty is found in every game mode besides Party Mode.
Activating Anti-team[]
Anti-team is triggered by hitting 3 viruses or more in a row in 1 minute. Mass will start to decay slightly faster than usual after hitting 2 viruses. The more subsequent viruses hit, the faster the rate of mass decay.
This affects teamers more, because when teamers hit viruses, they will usually give their loose pieces to their teammate(s), and won't be in 16 pieces anymore. So, if they hit more viruses, they are more likely to get the penalty sooner.
Note: Anti-team won't trigger if you hit a virus and start eating viruses using a larger cell.
Splitting[]
Anti-team can also be triggered by splitting too often. Teamers often use strategies that involve splitting at a frequent pace, but it is advisable to avoid splitting until you find a worthwhile target.
Stopping the Penalty[]
Once an anti-teaming penalty is active, mass of the player will vanish for some time and then stop. The cooldown does not depend on the player being alive or dead. If you respawn, then the policy will still be in effect, just lessened. However, it can be stopped by rejoining the server.
It is a strategy amongst team players to rejoin the server to ditch the penalty. One player stays in the game with all the mass of the team, while the other player rejoins. This can be done by randomly joining servers until landing again on the original server. But is it also possible to use a script/extension to immediately rejoin the same server. Some extensions have a hotkey that when pressed, the player will disconnect and immediately respawn in the same map.