According to UNAIDS, a member of the United Nations Development Group, 58 percent of people living with HIV/AIDS in sub-Saharan Africa are women. Although preventative drugs and condoms do block the transmission of HIV, neither are always practical,  available or affordable in developing nations. Help could be on its way, however, in the form of an anti-HIV intravaginal ring that is worn continuously for up to 30 days.

The device, which is known as the TDF-IVR (tenofovir disoproxil fumarate intravaginal ring), was developed at Illinois' Northwestern University by Prof. Patrick Kiser. It's essentially a looped polymer tube, that's filled with the powdered form of an anti-retroviral drug known as tenofovir – which ordinarily is taken orally.

When subjected to moisture, as would occur during intercourse, the polymer swells and releases some of the tenofovir. According to the university, this feature allows it to deliver "up to 1,000 times more of the drug than current intravaginal ring technology, which have release rates that decline over time."

Because the drug is delivered topically right to the place where it's needed, lower dosages are required than if it were to be administered orally. Additionally, women who are taking tenofovir orally have to remember to do so each day. The ring simply releases the drug as needed, plus it doesn't need to be applied immediately before intercourse, as does a condom or vaginal gel.

In recent tests on non-human primates, the TDF-IVR was shown to have a 100 percent success rate at blocking the simian human immunodeficiency virus. Human trials are scheduled to start next month, and will entail having 30 women using the ring over the course of 14 days.

If it proves safe and effective, it could ultimately also be used to deliver contraceptives, or antiviral drugs for other sexually-transmitted diseases.

A paper on the research was recently published in the journal Proceedings of the National Academy of Sciences.