disease question for Canadians entering US

[supercanada]

As I know, some disease cannot enter US, my question is, for disease related to sex problem,
1. whether US will know the disease of Canadians, share the medical database?
2. If the disease recovered, still have problem?
3. I heard if somebody has sex related problem, the doctor MUST inform the government, correct?
4. The Canadian government will tell US border?
Thanks