Answer
Syphilis, a sexually transmitted infection caused by the bacterium Treponema pallidum, plagued Delius in his later years. This debilitating disease severely affected his physical and mental well-being. As the ailment progressed, Delius's health deteriorated, often confining him to a wheelchair and causing excruciating pain. The impact of syphilis overshadowed his creativity, rendering it challenging for him to compose and conduct as effectively as he once had.