Prevalence is the number of people living with HIV/AIDS in a given year. HIV prevalence is the topic of the MMWR article, published October 3, 2008, called “HIV Prevalence Estimates—United States, 2006.”

This article shows that an estimated 1,106,400 persons are living with HIV (range: 1,056,400 – 1,156,400) in the United States (50 states and the District of Columbia). Of those individuals, approximately 1 in 5 (21%) do not know they are infected. Men who have sex with men (MSM) of all races, African Americans, and Hispanics/Latinos are disproportionately affected by HIV.

Because of changes in the national HIV surveillance data, the two estimates cannot be directly compared. Since the 2003 estimate, there have been improvements in the HIV reporting system: additional states have implemented name-based HIV reporting and the methods for de-duplication (to remove cases that might have been reported by more than one jurisdiction) have been improved. These improvements have allowed CDC to re-calculate the HIV prevalence estimate for 2003, which is now estimated to have been 994,000 (lower than the prior estimate of 1,039,000 – 1,185,000).

Using the refined estimate for 2003 and the new estimate for 2006, CDC estimates that there are approximately 112,000 more persons living with HIV in 2006 than in 2003.

There are a few reasons. People with HIV are living longer than in years past because of better treatments. Also, more people become infected with HIV than die from the disease each year. (In 2006, there were approximately 56,000 new HIV infections, versus approximately 14,000 deaths among persons with AIDS.)

The reduction from 25% to 21% reflects increased diagnoses among persons with HIV and a decline in deaths among people living with HIV over the three-year period. This change reflects successes in both getting more people with undiagnosed HIV tested and in the treatment of HIV disease.

Despite this progress, CDC estimates that there are still approximately 232,700 individuals in the US who do not know they have HIV.

HIV continues to affect primarily men in the United States. In 2006, men made up three quarters of all persons living with HIV (828,000 persons), and women made up one quarter (278,400 persons).

Overall, the article notes that:

• Persons infected through male-to-male sexual contact accounted for nearly half (48%, or 532,000 persons) of all persons living with HIV in the US in 2006.
• Persons infected through high-risk heterosexual contact (HRHC) accounted for over one quarter (28%, or 305,700) of all persons living with HIV.
• Persons infected through injection drug use (IDU) accounted for 19% of all persons living with HIV (204,600 persons).

Among men:

• MSM accounted for 64% (532,000) of men living with HIV.
• IDU accounted for 16% (131,500) of men living with HIV.
• HRHC accounted for 13% (104,000) of men living with HIV.

Among women:

• HRHC accounted for 72% (201,700) of women living with HIV.
• IDU accounted for 26% (73,100) of women living with HIV.

These new data confirm that HIV takes a disproportionate toll on African Americans and Hispanics/ Latinos. Although prevalence rates among whites were significantly less than those of African Americans or Hispanics and Latinos, whites made up more than one-third of all people living with HIV.

Overall:

• African Americans accounted for 46% of those living with HIV.
• Whites accounted for 35% of those living with HIV.
• Hispanics/Latinos accounted for 18% of those living with HIV.
• Asians/Pacific Islanders accounted for 1% of those living with HIV.
• American Indians/Alaska Natives accounted for less than 1% of those living with HIV.

Blacks:

Despite making up only 12% of the US population, blacks represented almost half (46%, or 510,100) of all individuals living with HIV in the United States.

• Black men have an HIV prevalence rate of 2,388 per 100,000 people, which is six times as high as the rate for white men (395 per 100,000).
• Black women have an HIV prevalence rate of 1,122 per 100,000 people, which is 18 times as high as the rate for white women (63 per 100,000).

Hispanics and Latinos:

Despite making up only 15% of the population, Hispanics/Latinos accounted for 18% (194,000) of all individuals living with HIV in the United States.

• Hispanic/Latino men have an HIV prevalence rate of 883 per 100,000 people, which is twice as high as the rate for white men (395 per 100,000).
• Hispanic/Latina woman have an HIV prevalence rate of 263 per 100,000 people, which is four times as high as the rate for white women (63 per 100,000).

These data tell us that 70% of individuals living with HIV in the United States are between the ages of 25 and 49 (770,000 persons). Twenty-five percent are aged 50 and older (280,000), and 5% are between the ages of 13 and 24 (56,500 persons).

Even though the growing number of people living with HIV in the United States is partially due to better treatments, it is also due to more people becoming infected with HIV each year. Therefore, there is a growing pool of people with HIV who must be reached with testing, medical care, and prevention services. Additionally, we must maintain our efforts to educate persons without HIV so that they will have the tools to reduce or eliminate behaviors that could put them at risk of infection.

HIV testing and prevention strategies work when we apply what we know. While the total number of people living with HIV in the US is increasing, the number of annual new HIV infections has remained stable in recent years. This stability is an important sign of progress, since a growing number of people living with HIV would be expected to increase opportunities for HIV transmission. It is possible to slow the spread of HIV in the United States if governments, businesses, individuals, and communities work together to make sure everyone in need receives testing and prevention services.