Decease is the correct spelling of the word that means to die. Desease is not a word in English. Disease is an illness.
The verb decease means to die but it is much more common to see decease in the noun or adjective form(deceased).
The deceased will always be remembered. (Noun)
That man is deceased. (Adjective)
“Desease” is not a word in the English language. It must be a misspelling of “Desease”.
A Disease is similar to an illness and examples include HIV and Chickenpox.