Complex sentence: In 2005, the prevalence of HIV infection among adults aged 15 to 49 was estimated to be 16.1 percent, and the primary mode of transmission was through heterosexual contact, with women at much greater risk for HIV infection than men.
Split into simpler sentences: In 2005, the prevalence of HIV infection among adults aged 15 to 49 was estimated to be 16.1 percent. The primary mode of transmission is through heterosexual contact, with women at much greater risk for HIV infection than men.