Just ahead of Thursday's World AIDS Day, the first study of its kind by the Centers for Disease Control finds only a small percentage of people with the virus that causes AIDS are being successfully treated.

FOX News Radio's Lisa Lacerra reports:

The study finding only about 1-in-4 Americans infected with HIV have the virus under control with medications.

The Centers for Disease Control and Prevention says part of the reason is that about 20% of people who have HIV don't know it.  It's possible to have the infection for years without displaying symptoms.  And health officials say part of the reason people are not getting better may be they are still early in their treatment or didn't stick with their medication due to money or other issues, and in a small percentage of patients, the medicine may not have worked.

Lisa Lacerra, FOX News Radio.