That's what I'm doing (even still had Wreathed items in my Vault that I threw into the fire) but still I only get my Pets and items burned and not myself which seems to be needed for to make any progress with the Achievement.

I see. I attempted it myself after I posted, and it only said that I had no items to burn (although it did burn the wreathed item). Maybe it's random when using a wreathed item? I guess it can't be too easy.

Thanks for these changes. Hm... Makes me regret the times I cured myself of the 2009 and 2010 zombie virus...