The invention relates to an infusion device for therapeutic use comprising a water-tight cover in the form of a housing, a housing part or a receptacle for holding said infusion device and a control system which is used for controlling the cover water tightness and comprises c) a medium arranged in the cover and characterized by at least one physical or chemical quantity variable according to the cover water tightness and d) an information system which automatically transmits at least one information signal when said quantity changes in such a way that the loss of the cover water tightness is indicated.