What is the major to become a social worker for people with HIV/AIDS?

I have talked to counselors and many do not know. One counselor told me to major in health science and maybe double major or minor in social work. He was not even sure about it. I plan to get a master’s degree in social work (MSW) but I am not sure if it applies for the career I am going for. Please help! I am frustrated and confused. =/