Let's have some diseases that affect objects!

[Marquesas]

EG, something that dissolves all of your clothes

Maybe.

Or makes food/drink you pick up go bad

Possibly (define 'bad food', though). Although this would probably be a mutation, not a disease.

or eats plastic (or petrochemicals!)

Perhaps (define 'plastic', though).

Also, the title made me think of coughing, sneezing, self-igniting toolboxes.