A method and solution or gel composition containing activated chlorine dioxide and phosphates, such as disodium hydrogen phosphate, sodium dihydrogen phosphate, trisodium phosphate, and sodium monofluorophosphate, is disclosed for lubricating the vagina and for treating HIV. The preferred concentration ranges are between about 0.005% to about 2.0% chlorine dioxide, and between about 0.02% to about 3.0% phosphate. The phosphate compound retards escape of chlorine dioxide in the pH range of about 6.0 to 7.4, at which pH the chlorine dioxide becomes activated and releases sufficient chlorine dioxide to reduce motility and become lethal to the involved micro-organisms.