Comprehensive Overview of HIV/AIDS:
State of Kentucky Mandatory Training

HIV/AIDS Basic Medical and Epidemiological Information

The most commonly accepted theory is that HIV, first identified in 1983, came from a simian (monkey) virus that spread to humans in Africa during the 1930's and 1940's. The transmission of HIV has been driven by multiple changes in migration, housing, travel, sexual practices, drug use, war, and economics that have affected both Africa and the entire world since 1940.

AIDS was first recognized in the United States in 1981; the US Centers for Disease Control and Prevention (CDC) issued a warning about the symptoms that were caused by what we now know to be HIV. In the Commonwealth of Kentucky, the first reported case of AIDS was in 1982. Since then, the number of AIDS cases has continued to increase both in the U.S. and other countries.

People who are infected with HIV come from all races, all countries, sexual orientations, genders, and income levels. Globally, most of the people who are infected with HIV have not been tested, and are unaware that they are living with the virus.

The Human Immunodeficiency Virus (HIV) is the virus that attacks the immune system, damaging the body's ability to fight the organisms that cause infections and diseases. It is the virus that leads to a diagnosis of AIDS. But HIV and AIDS are not the same. Everyone who has AIDS has been infected with HIV; but everyone with HIV infection does not have AIDS.

This highly magnified transmission electron micrographic (TEM) image revealed the presence of mature forms of the human immunodeficiency virus (HIV) in a tissue sample under investigation. Courtesy of US Public Health Image Library.

HIV has divided into two primary strains: HIV-1 and HIV-2. HIV-1 is found throughout the world. HIV-2 is found primarily in West Africa, where the virus may have been in circulation since the 1960s - 1970s. Both HIV-1 and HIV-2 have several subtypes. It is virtually certain that more undiscovered subtypes are in existence now. It is also probable that more HIV subtypes will evolve in the future.

Acquired ImmunoDeficiency (sometimes Immune Deficiency) Syndrome (AIDS) is a complex of symptoms and diseases caused by the HIV virus as it impacts the immune system. It is an acquired disease. As HIV damages the immune system, infected persons become vulnerable to opportunistic organisms. These opportunistic infections generally do not pose a threat to persons with healthy functioning immune systems. The diagnosis of AIDS requires a positive HIV antibody test or evidence of HIV infection and the appearance of some very specific conditions/diseases.

A positive HIV test plus one or more of the following:

• Candidiasis, of esophagus, trachea, bronchi or lungs.
• Cervical cancer, invasive.
• Coccidioidomycosis, extrapulmonary.
• Cryptococcosis, extrapulmonary.
• Cryptosporidiosis with diarrhea greater than one month.
• Cytomegalovirus of any organ other than liver, spleen, or lymph nodes.
• Herpes simplex with mucocutaneous ulcer lasting longer than one month or bronchitis, pneumonitis, esophagitis.
• Histoplasmosis, extrapulmonary.
• HIV-associated dementia: disabling cognitive and/or motor dysfunction interfering with activities of daily living.
• HIV-associated wasting: involuntary weight loss >10% of baseline plus chronic diarrhea (2 loose stools/day for 30 days) or chronic weakness and documented enigmatic fever 30 days.
• Kaposi's sarcoma.
• Isosporiasis, chronic intestinal (greater than 1 month's duration).
• Lymphoma of brain.
• Lymphoma, non-Hodgkin's of B-cell or unknown immunologic phenotype and histology showing small, noncleaved lymphoma or immunoblastic sarcoma.
• Mycobacterium avium complex or M. kansasii, disseminated.
• Tuberculosis.
• Pneumocystis jiroveci (formerly carinii) pneumonia.
• Pneumonia, recurrent-bacterial (2 episodes in 12 months).
• Progressive multifocal leukoencephalopathy.
• Salmonella septicemia (non-typhoid), recurrent.
• Toxoplasmosis of internal organs.

When HIV enters the bloodstream, the virus seeks a particular lymphocyte, the CD4 cell (also called the T4 cell or T-Helper lymphocyte), which functions to "orchestrate" the immune system in the event of attack from pathogens. Upon contact with HIV the T-cell signals the production of antibodies. Particularly frustrating about HIV is that the antibodies produced to fight the virus are not able to do so, since HIV captures the cells that signal antibodies to be produced. The result is an eventual decline of the immune system.

AIDS Surveillance Case Definition

In 1987, the CDC defined AIDS using a positive HIV antibody test plus a list of conditions that indicated a deficient immune system. The original case definition of HIV infection was based on the clinical symptoms seen in men. In 1993, the CDC revised the classification system for HIV infection and expanded the case definition for AIDS to include more conditions and a variety of CD4-cell counts; it included invasive cervical cancer, obviously a condition found only in women. The revised definition meant that more people were considered to have AIDS. That year there was a "jump" in the number of people with AIDS which reflected the change in classification system.

An AIDS diagnosis is only made by a licensed healthcare provider, based on a confirmed HIV test result, the presence of certain defining physical conditions, and the person's CD4-cell count. HIV has a wide spectrum of clinical presentations in children. The CDC developed a revised pediatric HIV classification system in 1994, to clarify HIV-infected pediatric patients into categories based on their immune system, CD4 cells, and clinical category. Pediatric classification of AIDS is different than the classification for adults.

The 1993 AIDS Surveillance Case Definition for Adolescents and Adults, which is the most current definition, is comprised of a 3 x 3 staging system. In this definition, any person who is HIV-infected and has either an AIDS indicator condition or a CD4+, the T-cell count, less than 200 cells/mm3, or less than 14%, is considered to have AIDS.

The 2008 revised HIV case definition classifies HIV infection among adults and adolescents and among children. The revised definition incor­porates an HIV infection classification staging system that includes AIDS (HIV infection, stage 3). The stages of HIV infection are defined as follows (CDC, 2012):

• HIV infection, stage 1: No AIDS-defining condi­tion and either CD4 count of ≥500 cells/μL or CD4 percentage of total lymphocytes of ≥29.
• HIV infection, stage 2: No AIDS-defining condi­tion and either CD4 count of 200–499 cells/μL or CD4 percentage of total lymphocytes of 14–28.
• HIV infection, stage 3 (AIDS): Documentation of an AIDS-defining condition or either a CD4 count of <200 cells/μL or a CD4 percentage of total lym­phocytes of <14. Documentation of an AIDS-defining condition supersedes a CD4 count or per­centage that would not, by itself, be the basis for a stage 3 (AIDS) classification.
• HIV infection, stage unknown: No reported information on AIDS-defining conditions and no information available on CD4 count or percentage.

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