HIV is estimated to have caused 65 million human infections worldwide with 25 million deaths since the beginning of the epidemic (8), according to the World Health Organization and the Joint AIDS United Nations program data as of the end of 2005. The epidemic has different characteristics in different geographic areas, but overall remains the fourth leading cause of death, with a staggering 95% of those occurring in young adults in the developing world, mostly in sub-Saharan Africa. The epidemic continues to intensify in Africa and there are alarming signs that prevalence rates will take off in areas of Asia and Eastern Europe.
In the United States, there were an estimated 1.2 million people living with HIV/AIDS (8,9). The majority of people with HIV in the United States are men who have sex with men, and sex between men remains the dominant mode of transmission. One of the striking facets of the epidemic in the United States is the concentration of HIV infections among African-Americans. Despite constituting only 12.5% of the country's population, African-Americans accounted for 48% of new HIV cases in 2003. AIDS has become one of the top three causes of death for African-American men aged 25 to 54; it is the number one cause of death for African-American women aged 25 to 34 years, in most of these cases acquired via heterosexual transmission (9).
TABLE 1 Centers for Disease Control Definition of CD4 Lymphocyte Count and Clinical Categories of HIV Infection3
Categories of CD4 cell counts Category 1: >500 cells/mL Category 2: 200-499 cells/mL Category 3: <200 cells/mL Clinical categories Category A
Asymptomatic HIV infection Persistent generalized lymphadenopathy Acute (primary) HIV infection Category B
Candidiasis, vulvovaginal; persistent, frequent, or poorly responsive to therapy Cervical dysplasia (moderate or severe)/cervical carcinoma in situ Constitutional symptoms such as fever (38.5°C) or diarrhea lasting greater than 1 mo Hairy leukoplakia, oral
Idiopathic thrombocytopenic purpura
Pelvic inflammatory disease, particularly if complicated by tubo-ovarian abscess Peripheral neuropathy Category C
Candidiasis of bronchi, trachea, or lungs Candidiasis, esophageal Cervical cancer, invasive
Coccidioidomycosis, disseminated or extrapulmonary Cryptococcosis, extrapulmonary Cryptosporidiosis, chronic intestinal (>1 mo duration) Cytomegalovirus disease (other than liver, spleen, or nodes) Cytomegalovirus retinitis (with loss of vision) Encephalopathy, HIV-related
Histoplasmosis, disseminated or extrapulmonary Isosporiasis, chronic intestinal (>1 mo duration) Kaposi's sarcoma
Lymphoma, Burkitt's (or equivalent term) Lymphoma, immunoblastic (or equivalent term) Lymphoma, primary, of brain
Mycobacterium avium complex or Mycobacterium kansasii, disseminated or extrapulmonary
Mycobacterium tuberculosis, any site (pulmonary or extrapulmonary) Mycobacterium, other species or unidentified species, disseminated or extrapulmonary
Pneumocystis jirovecii (carinii) pneumonia Pneumonia, recurrent
Progressive multifocal leukoencephalopathy Salmonella septicemia, recurrent Toxoplasmosis of brain Wasting syndrome due to HIV
aCategories A3, B3, C1, C2, and C3 meet the case definition for AIDS. Source: From Refs. 7, 31.
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