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AIDS, HIV

Acquired Immune Deficiency Syndrome (AIDS) is an infectious disease caused by the human immunodeficiency virus (HIV). The virus progressively destroys the immune system of the person infected.

Routes of infection

HIV is transferred from one person to another through contaminated bodily fluids (semen, saliva, blood). The most frequent routes of infection are unprotected sexual contact and the use of non-sterile syringes, e.g. drug use. Blood transfusions are also a possible source of infection, although in Germany today routine examinations of blood donors has all but eliminated this risk.

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Images, photos and illustrations of AIDS in the Third World. AIDS viruses as 3D graphics. AIDS prevention. All HIV viruses as a medicalpicture image selection.

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History of AIDS

HIV is closely related to viruses that trigger AIDS-like symptoms in primates. It is generally accepted that one of these virus types was transferred to humans at the beginning of the 20th century, although there are indications of isolated cases even earlier. Absolute facts of time, location, host, type and number of transmissions are unknown. SIV is a virus that is nearly identical to HIV in humans and has been found in chimpanzees. According to recent studies by virologists at the University of Alabama at Birmingham, HIV-1 that evolved from the SIV virus found in chimpanzees is the cause of the deadly immune deficiency diseases. Through a genetic analysis, scientists were able to show that the SIV virus is a combination of three viral strains that occur in certain long-tailed monkeys. Since chimpanzees hunt and eat long-tailed monkeys, the chimpanzees must have been infected with the two viral strains, which then formed the SIV virus in their bodies. According to the researchers, transmission of the SIV virus to humans likely took place in the 1930s through the consumption of chimpanzee flesh. Further scientific research has shown that the HIV virus first occurred in West Africa, but there is no absolute certainty that there were not multiple virus focuses, one of which possibly in South America. The first blood sample proven to have contained HIV was taken in 1959 in the Congo. Additional samples come from an American (1969) and a Norwegian sailor (1976).

The agent - The HIV virus (AIDS virus)

HIV stands for human immunodeficiency virus. The HIV virus infects human T cells and thus destroys the immune system. The HIV virus is a spherical virus of about 100nm in diameter and belongs to the family of retroviruses. It was discovered by Luc Montagnier, a French virologist. To reproduce, the virus needs body cells that carry the CD4 receptor on their surface. The gp120 surface protein of HIV forms a connection with the CD4 receptors. The T lymphocytes (T4 cells) responsible in humans for antibody formation are the primary site of CD4 receptors. The HIV virus embeds its RNA genome in DNA form in the genome of the host cell (endogenous retroviral genome) where it begins to produce virus proteins and enzymes needed by the virus. This makes it particularly difficult to combat the infection, since the affected host cell is continually producing new viruses. Therefore, researches are trying to develop CD4 vaccines that prevent the HIV virus from docking with the T4 cells or to inhibit reverse transcriptase to abort DNA synthesis.

Pathogenesis

Not everyone infected with the HIV virus automatically has AIDS. The purely clinical diagnosis of "AIDS" is typically only given after a certain degree of destruction of the immune system. It is defined by the occurrence of so-called opportunistic infections. These infections are caused by agents that can first cause illness by the immune deficiency resulting from the HIV infection. The T helper cell count in the blood of someone infected by HIV is used to measure the destruction of the immune system. The standard threshold is reached when the T cell level of a patient falls below 200-400/µl blood. Falling below this threshold represents an indication of treatment.

Epidemiology

In 2003, 42 million people were infected with AIDS; in 2001 alone, approx. 5 million people were newly infected with the virus and 3 million with AIDS died from the disease. Ethnicity affects the course of the disease and can be attributed to inherited genetic characteristics. On average, the disease breaks out and progresses fastest in Africans and Asians. The onset of illness is significantly longer for 10-15% of the population in Western Europe and an estimated 1% take 10-15 years (perhaps never) for onset to occur. The average onset for the US populations is between the two. It is accepted that a mutation of the CCR5 gene provokes the immunity. If the mutation is homozygous, then HIV practically no longer breaks out. If it is heterozygous, then the course of the infection is slowed. This mutation in a few Europeans likely occurred 700 years ago. Presumably, it was advantageous since it also provided a certain immunity against the plague or smallpox. This characteristic spread in the population through natural selection during the epidemics. It so happens that this characteristic also demonstrates an immunity today against HIV and thus against the outbreak of AIDS.

No all-clear on HIV, AIDS in Germany

The latest half-yearly HIV/AIDS report by the Robert Koch Institute reveals that the number of newly diagnosed HIV infections in Germany showed no reduction in 2004 at just under 2000. Moreover, the rise observed in recent years in the number of cases among men who have sex with men has continued. Compared with the previous year, there was a 6% increase in the number of new HIV diagnoses in this group. In the case of syphilis, the number of cases registered rose to 3,345 in 2004 (from 2,934 in 2003). Here, too, the increase is particularly marked among men with same-sex contacts. According to the latest representative survey conducted by the Federal Centre for Health Education (BZgA) on "AIDS in the public consciousness 2004", protective behavior among sexually active people has diminished in certain groups. So far, a total of 1,928 new cases of HIV infection have been registered for 2004. In 2003 the figure was 1,979. At almost 47%, men who have sex with men form the largest group of those affected. In the group of men who have sex with men, syphilis represents a particular threat as a pacesetter for HIV/AIDS. In the sector of heterosexual sexual contacts, special attention must be drawn to the growing threat posed by the high HIV infection rates in Eastern Europe and the risks of infection through increasing prostitution. (Source: rki)

Weblinks

• Aids Info of the U.S. Department of Health and Human Services
• AIDS-INFO.NET
• Excerpts are based on the AIDS article from the free encyclopedia Wikipedia and are under the GNU Free Documentation License. There is a list of the authors available on Wikipedia.

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Last modified: Mon Feb 01 2010