Writing Stack Exchange is a question and answer site for the craft of professional writing, including fiction, non-fiction, technical, scholarly, and commercial writing. It only takes a minute to sign up.
I suppose you could say, "The disease follows me around...
like a moth drawn to a flame. (pretty cliche)
like a crazy ex. (also cliche)
like a bloodhound tracking down a stag.
like a mosquito/Great White/vampire
drawn to blood.
like a curse/nightmare that reminds me everyday of my terrible luck/life.
like the soul of a dead man who swore upon his
deathbed that he would haunt me until I meet my demise and take my
rightful place in the underworld." (only if you want to be super dramatic)
Depending on the context and if you are willing to reword the sentence a bit, you could describe the disease as a scar. Sorry, none of these are entirely crude, but I hope they at least help you come up with something far better than my tired mind could. I'll write anything else I come up with. Good luck!