Those damn Dust Men destroyed the clinic I had on one of the piers. Go break some bones, teach them not to come around here.
― Medic to Cole
"Infestation" is a side mission in Infamous.
In the Warren, Cole meets a medic who requests that he clears out the Dust Men from his nearby clinic, that way he can return to business.
By now, you should know what the objective is. Head to the marked location and take down the Dust Men any way possible.
Completing this side quest unlocks another medical clinic, and rewards the player with 100 Experience points. Also, enemy activity in the Warren will be slightly reduced.