From The TimeSplitters Wiki

The fire games in Timesplitters have been in both TS2 and TSFP (flame tag was not in TSFP). They both use flames as their main form of play.

Flame Tag

Flame Tag is a very strange and easy to win mode. One player starts of on fire and passes it on to the other players, losing the fire when they touch other people. The player with the least time holding the flame at the end wins. This mode usually ends up with various winners, since it is very easy to avoid the person on fire. It did not appear in TSFP.

Virus

Virus has appeared in both TS2 and TSFP. One player starts of on fire, and tries to start other people on fire. A player cannot lose their fire, and will stay on fire until the end of the match. The last person without the virus will win the match, and if time runs out with two or more people untagged, they all win. The fire in Virus in green. The virus cannot be gotten rid of, even if the player with it is killed. A suicide will result in getting the virus. In TSFP, players with the virus are sped up.