ATrain Education


Continuing Education for Health Professionals


Module 2

Epidemiology of HIV

The human immunodeficiency virus (HIV) has infected tens of millions of people around the world in the past three decades, with devastating results. In its advanced stage—called acquired immunodeficiency syndrome (AIDS)—infected individuals have no protection from diseases that threaten their immune systems. Although medical treatment can delay the onset of AIDS, no cure is available.

Worldwide, the overall growth of the AIDS epidemic began to stabilize in the late 1990s and the annual number of new HIV infections has been steadily declining since then. As treatment has become more effective, people with HIV are living longer and, consequently, the number of people living with HIV worldwide has increased to about 35 million people (UNAIDS, 2013a). There has been a 33% decline in new infections since 2001. Nevertheless, 2.3 million people worldwide were new HIV infections in 2012 (UNAIDS, 2013a).

Although there are notable exceptions within certain high-risk groups, the number of AIDS deaths declined to 1.6 million deaths in 2012 (UNAIDS, 2013a). In many countries, prevention efforts among sex workers and men who have sex with men still lags behind prevention efforts for other high-risk groups. In addition, the prevalence of HIV among injection drugs users remains high and prevention efforts remain low in many countries (UNAIDS, 2013a).

Much of the success in reducing the number of deaths related to HIV is due to an increase in the number of HIV-infected people receiving antiretroviral therapy. This prevents HIV-related illness and death, reduces the risk of HIV transmission, and reduces the spread of tuberculosis. In low- and middle-income countries, the number of people receiving antiretroviral therapy has increased dramatically over the past ten years, from 300,000 in 2002 to 9.7 million in 2012 (UNAIDS, 2013b). The United Nations has established a goal of providing antiretroviral therapy to 15 million people by 2015.

The dimensions and pace of the epidemic nevertheless remain staggering—especially in sub-Saharan Africa, home to 12% of the world’s population but 70% of all new HIV infections in 2012. In eight countries in this region, 10% of the adult population is estimated to be HIV-positive (KFF, 2013). However, since 2001 the annual number of new HIV infections among adults in sub-Saharan Africa has declined by 34%. Two other regions, however, experienced significant increases in mortality from AIDS: Eastern Europe/Central Asia and the Middle East/North Africa (UNAIDS, 2013b).

In the United States

Since the height of the epidemic in the mid-1980s, the annual number of new HIV infections in the United States has been reduced by more than two-thirds, from roughly 130,000 to 50,000 people newly infected each year. Overall, more than 1.8 million people in the United States are estimated to have been infected with HIV, including over 650,000 who have already died. Today, more than 1.1 million people in the United States are living with HIV and about 200,000 are unaware that they are infected with the virus (CDC, 2013a).

By transmission category, the largest number of new HIV infections currently occurs among men who have sex with men of all races and ethnicities, followed by African American heterosexual women. By race/ethnicity overall, African Americans are the most heavily affected, followed by Latinos (CDC, 2013a).

Estimated Number of New HIV Infections in U.S., 2010

graph: estimated new HIV infections in US (2010)

Subpopulations representing 2% or less of the overall US epidemic are not reflected in this chart.

Estimated new HIV infections in the United States, 2010, for the most affected subpopulations.

MSM = men who have sex with men, IDU = injection drug users. Source: CDC, 2010.

In Kentucky

As of June 30, 2013, Kentucky had recorded 8,904 cumulative AIDS cases since the health department’s surveillance program began in 1982. The majority (83%) of HIV infections diagnosed in Kentucky have been among males. Among all males, 35% percent of cumulative cases were aged 30 to 39 years at the time of diagnosis (KCHFS, 2013). As in the United States generally, minorities in Kentucky are disproportionately affected by HIV/AIDS, with African Americans accounting for about 40% of the cumulative cases and Hispanics 19%.

People Newly Diagnosed with HIV in Kentucky

In 2011 (latest data available), 55% of newly diagnosed HIV cases were among white, non-Hispanic Kentuckians. Related to their representation in the general population, there are higher rates of infection among blacks and Hispanics. Blacks accounted for 35% of new HIV infections diagnosed in 2011, yet comprised just 8% of Kentucky’s population in 2011. Similarly, Hispanics accounted for 7% of newly diagnosed HIV infections in 2011, yet comprised only 3% of the population in that year. AIDS is the fourth leading cause of death among Kentucky’s young (25–44) African American men (KCHFS, 2013).

Pediatric Cases

There have been 81 pediatric HIV infections reported to the Kentucky HIV/AIDS surveillance program since AIDS reporting began in 1982. The majority of reported pediatric infections (75%) were due to perinatal transmission through an HIV-infected mother, 11 infections were reported with a primary exposure route of pediatric hemophilia or coagulation disorders, and 2 infections were reportedly due to pediatric transfusion or transplant (KCHFS, 2013).

Since 1991 there have been no pediatric HIV infections with hemophilia or coagulation disorders reported as the route of exposure in Kentucky. The two pediatric infections reported with pediatric transfusion or transplant as the risk factor were diagnosed in 1987 or earlier. Thirty-six of the 43 pediatric HIV infections among blacks were due to perinatal exposure, compared to 36 pediatric HIV infections among whites. Only one pediatric HIV infection has been reported among Hispanics (KCHFS, 2013).

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