Complex sentence: Without treatment, average survival time after infection with HIV is estimated to be 9 to 11 years, depending on the HIV subtype, and after diagnosis of AIDS where treatment is not available ranges between 6 and 19 months.
Split into simpler sentences: Without treatment, average survival time after infection with HIV is estimated to be 9 to 11 years, depending on the HIV subtype. After the diagnosis of AIDS, if treatment is not available, survival ranges between 6 and 19 months.