Obviously the first verse is about nightmares or having trouble with sleep, potentially the stress of a secret relationship is too much, "I feel like I'm the only one who can carry your disease" meaning
He's saying the guy is suffering in his head because though the "safety" of being "in the closet" seems easier its actually making things worse because the guy has to always watch himself.
The last verse is about a moment of intimacy, the subject feels no one will understand or accept him so the he tells the singer he's the only one who can carry his "disease".
Seeing the lyrics I agree with mouaii.
Obviously the first verse is about nightmares or having trouble with sleep, potentially the stress of a secret relationship is too much, "I feel like I'm the only one who can carry your disease" meaning
He's saying the guy is suffering in his head because though the "safety" of being "in the closet" seems easier its actually making things worse because the guy has to always watch himself.
The last verse is about a moment of intimacy, the subject feels no one will understand or accept him so the he tells the singer he's the only one who can carry his "disease".