Diagnoses of HIV infection are down one-third overall in the United States over 10 years. The number of cases reported each year dropped from 2002 to 2011. Nearly every demographic saw lower instances of infection with HIV, with the exception of younger and older men who have had male lovers.

A total of 493,372 people were diagnosed with HIV during the years examined by the researchers. In 2002, 24.1 people out of every 100,000 were found to be HIV-positive. By 2011, that number declined to just 16.1. On July 16, the United Nations announced just 2.1 million new diagnoses of AIDS, just 62 percent of the number reported in 2001.

The Centers for Disease Control and Prevention estimates roughly 1.1 million Americans are living with HIV in their bodies, although 18 percent are unaware of it.

Women, and people aged 35 to 44, experienced the most dramatic drops in HIV infections. This improvement in new HIV cases in America parallels declines in much of the rest of the world. Antiretroviral therapy, consisting of three or more antiretroviral (ARV) drugs given in combination, has helped to slow progression of the disease worldwide.

Homosexual and bisexual men were found to have an overall steady rate of infection as a group. Different ages of the men were affected unevenly by the disease. Infection rates climbed for the youngest of the group, ages 13 to 24. Men between 45 and 54, as well as those in the 55+ age bracket, also saw a greater number of cases. For males between the ages 35-44 who came into sexual contact with other men, HIV infection declined.

The hardest-hit of all groups were the youngest. Young men 13-24 who experienced homosexual sex shot up by 132.5 percent.

As testing patterns and methodologies change, so can the diagnosis rate of diseases.

The study made note that "HIV testing services were expanded during the analysis period and early outcomes of testing initiatives often indicate increases in diagnoses."

Data was collected from the National HIV Surveillance System, managed by the CDC. The data collected was made available through program and funding legal requirements.

"Accurate HIV diagnosis data recently became available for all states, allowing for the first time an examination of long-term national trends," researchers wrote in background text for the article.

Study of the rate of AIDS infections in the United States was published in the Journal of the American Medical Association.