I believe the symptoms of mental health can be learned by others, but the illness it self, no that can not be caught.

I once worked with a woman who was born deaf...back when that was automatically grounds for being institutionalized . She grew up surrounded by unmedicated chaos and she learned those behaviors. Once they started to look at ways to de-institutionalize many people she was taught ASL( she was in her 30's). She learned quickly and was eventually sent to the house I worked at. When she was frustrated or confused she would act out in a way interpreted as MI. But she herself wasn't MI or DD although she had those labels.

I also believe there are people who for one reason or another desire attention and mimic MI behaviors. I am however not sure if doing that might not be a type of MI in itself or just some sort of hole inside a person that would drive them to desire a MI.