Blue expanding circle around players

Sometimes as I am playing TF2 I will see a player with a glowing, cyclically expanding circle around the base of the model. Does this mean anything?

Unfortunately I have not been able to get a screenshot of this phenomenon. There was one time a medic was near me and both of us had the circle. Could he have had something to do with it?

Solution 1:

There are multiple weapons that have that effect.

• Buff Banner
• Battalion' Backup
• Concheror

all have the same turquoise/orange effect, which you can see in the demonstration videos of those pages.

• The Quick Fix Über displays the same effect in blue/red, as you can see for example here. (Demonstration)

Finally the Amputator taunt called Medicating Melody also displays this effect.

If you want to understand which effect it really is, you need to look for the source. The soldier's banners get raised while active and have the special color. Which of the banners is being used can only really be said by looking at the soldier. The Amputator taunt can easily be identified by the taunting medic. The Quick Fix Über only affects the medic and his current healing target, while the other items affect everybody who is in a certain radius.

Solution 2:

The Medic is likely performing the Amputator taunt, which causes everyone around him to bear the glowing circle and receive passive healing for a few seconds.

I observe the same effect when a Quick-Fix charge is deployed, but I'm not sure if it's another buff or if it's coming from the Quick-Fix.