A pump module for an infusion pump includes a plunger-cylinder unit that can be coupled to the infusion pump in order to deliver fluid from a fluid feed line into a fluid drain line to a patient. The plunger-cylinder unit has a delivery chamber that is fluidically connected to the fluid feed line and the fluid drain line. The delivery chamber is delimited by the cylinder (14). The plunger can be moved linearly/back and forth in the axial direction. A plunger seal seals the plunger in relation to the cylinder. The section of the wall of the cylinder, over which the plunger seal passes during the back-and-forth motion of the plunger, is sealed in a sterile manner in relation to the surroundings.
