About 1 million Americans living with HIV

July 2005

ATLANTA — At the end of 2003, roughly 1 million Americans were living with HIV; blacks and gay and bisexual men were the most severely affected, according to HIV research data presented at the 2005 National HIV Prevention Conference.

About one-fourth of those do not know they have HIV, said M. Kathleen Glynn, DVM, MPVM, epidemiologist, division of HIV/AIDS prevention, CDC. Modeling results also indicated that blacks and men who have sex with men (MSM) remain the most affected populations; women and high-risk heterosexuals, however, do not fall far behind compared with years past.

“We have to equip them with the knowledge and services needed to stay healthy and help protect others from infection,” she told Infectious Disease News.

Glynn provided attendees with new figures based on refined estimation methods. These data currently provide the clearest picture, to date, of the scope of the epidemic overall and among specific racial, ethnic and risk groups, she said.

“Efforts must be continued to ensure that persons at risk for HIV find out their serostatus and are appropriately linked to care and prevention services,” the researchers wrote in their abstract. “These results show that HIV/AIDS surveillance data, representing persons diagnosed with HIV infection, can be used to provide robust estimates of the overall HIV prevalence in the United States.”

HIV/AIDS prevalence

Since the CDC’s last HIV estimates, released in 2002, more data have become available about HIV diagnoses before progression to AIDS. Glynn and colleagues used this information and two different modeling methods to determine HIV prevalence across the nation. However, both methods used HIV/AIDS surveillance data reported to the CDC through June 2004.

The researchers found with method A that there were an estimated 925,000 to 1.025 million people living with HIV/AIDS at the end of 2003. Of these, 366,000 were living with HIV, 395,000 had AIDS and 164,000 to 264,000 were unaware of their serostatus, according to the abstract.

Using a back-calculation model, Method B’s results indicated that overall HIV estimated prevalence was 1.039 million to 1.185 million. Of these, 417,000 people were living with HIV, 415,000 had AIDS and 252,000 to 312,000 were undiagnosed.

Researchers were also able to examine the magnitude of the epidemic within specific populations.

Almost half (47%) of those estimated to be living with HIV were black. White people accounted for 34% of those living with HIV, and 17% were Hispanic. Asian/Pacific Islanders and American Indians/Alaska Natives each represented about 1% of the HIV population.

By risk group, the researchers found that 45% were MSM, followed by an estimated 27% who acquired the disease through high-risk heterosexual contact and 22% from injection drug use. MSM and injection drug users accounted for 5%.

Males represented 74% of the HIV population. However, according to Glynn, this makeup may begin to change.

“More diverse populations are affected [by HIV] than ever before – and there are a wide range of factors influencing transmission in different groups,” Glynn said. “The solution will require culturally appropriate and carefully tailored approaches.”

In years to come

The modeling methods also revealed a pattern about how the HIV population may change in the future.

Glynn and colleagues evaluated the total diagnosed population into those that progressed to AIDS and those in earlier stages of disease and found that females, non-Hispanic blacks and those who acquire HIV through high-risk heterosexual contact currently account for a higher proportion of those living with HIV than they do among those living with AIDS.

“Treatment successes have brought new challenges. While advances in treatment are a godsend for HIV-positive individuals — resulting in longer, healthier lives – this also means there is a growing population in need of services,” she said.

Likewise, Glynn added that increased prevalence means an increased opportunity for HIV transmission and an increased need for HIV testing and prevention services and programs. Efforts to reduce HIV cases must be designed to meet the needs of all populations.

“The medical and public health community have to help people maintain safe behaviors over a lifetime, not just in a crisis mode,” she said.

Although future prevalence trends depend on trends in new infections, diagnoses, disease and deaths, these findings suggest that these populations may comprise an even greater percentage of HIV-positive people in years to come.

Therefore, in addition to updating overall prevalence estimates, Glynn and colleagues sought to determine how many individuals living with HIV are unaware of their serostatus.

Results indicated that, as of 2003, between 24% and 27% of individuals living with HIV remained undiagnosed. Researchers said they believe these estimates point to an increased need for HIV testing, prevention and treatment services to slow the U.S. HIV/AIDS epidemic.

A need for surveillance

National AIDS case surveillance has been conducted throughout the United States since the 1980s and is used to generate an active picture of the AIDS epidemic to provide information about people living with AIDS, Glynn said.

However, there is no national HIV surveillance system that monitors and tracks HIV diagnoses, despite the fact that “comprehensive national HIV surveillance data are critical,” she said. If available, such data could be used to estimate the number of people living with HIV/AIDS, both diagnosed and undiagnosed.

The researchers stressed that the estimation methods include uncertainty, and, like all estimates, are only as good as the data upon which they are based.

Previous estimates stated that 850,000 to 950,000 people were living with HIV at the end of 2000, approximately 25% of whom did not know they were infected. Researchers based these estimates on various data sources and used projections that assumed a constant number of new HIV infections and AIDS deaths annually since 1998.

Newer back-calculation methods take advantage of the increasing availability of information on HIV detection before progression to AIDS.

The wide range for the prevalence estimates and the estimates for the proportion of individuals who remain undiagnosed is largely the result of continued gaps in data on HIV diagnoses across the nation.

CDC officials said that continued efforts toward a national tracking system are critical to improve the precision of future HIV prevalence estimates and to accurately monitor the course of the HIV epidemic, Glynn said. It is also important to direct prevention efforts to those populations in greatest need.

For more information:

• Glynn L. Estimated HIV prevalence in the United States at the end of 2003. Plenary session T1-B1101. Presented at the 2005 National HIV Prevention Conference. June 12-15, 2005. Atlanta.