In this Chapter, "relevant disease" means, in relation to any claim for benefit in respect of a prescribed disease, the prescribed disease in respect of which benefit is claimed, but does not include any previous or subsequent attack of that disease, suffered by the same person, which, under Chapter 3 of this Part, is or has been treated - (a) as having developed on a date other than the date which, under the said provisions, is treated as the date of development for the purposes of the claim under consideration, or (b) as a recrudescence of a disease for which compensation has been paid or awarded under the Workmen's Compensation Acts.