I honestly have no idea what this is trying to say.
Writing a letter to your diseases makes them go away apparently.
Dear AIDS,
Even though you are slowly and painfully eating away at my body, I still love you and know that there is good in you. Now, please stop killing me.
Love, guy with AIDS
Is this a thing in the American school system?
There's an episode of the series Louie where Louis CK's daughter must write a letter to AIDS for school.
Louie jokes that she could write "Dear AIDS, please cut it out" but she scoffs at him for not taking the task seriously.
