Is there any known diseases that we have created ?

Answer 1

U.S., Soviet, and Chinese Military scientists created numerous strains of "superbugs",modifying known diseases into fast, incurable strains for use as biological warfare weapons.
Super infectious strains of Anthrax, Botulism, Flu's, and other diseases have been created.
....Possibly including HIV and H5N1.(Don't count on them ever admitting one "got away", though.)

Answer 2

diabetes
heart disease
some cancers
mutated versions of some viral and bacterial infections


There are lots more