M.L. is a 26-year-old homosexual man admitted to the hospital for progressive respiratory distress, fever, weakness, and chronic diarrhea. He tested HIV positive about 3 years ago, but his infection has remained asymptomatic until 2 months prior to admission. Pneumocystis jiroveci (carinii) pneumonia was suspected and confirmed by culture. Laboratory analysis demonstrates a low CD4+ count of 185 cells/ml. HAART treatment with the antiretrovirals azidothymidine (AZT), efavirenz (Sustiva), and ritonavir (Norvir) was started 2 months ago.
M.L.'s sexual partner recently tested negative for HIV. What conclusions can be made about his HIV status?