Human Immunodeficiency Virus Underlying Cause
HIV weakens the immune system, which fights infection. The virus attacks white blood cells, which help kill bacteria, viruses, and fungi. After the initial infection with HIV, a person may have no signs of AIDS for months to years, because it takes time for the virus to destroy the white blood cells. When enough of the white blood cells are destroyed, then the immune system becomes deficient: it is unable to protect the body from infection. Those who develop AIDS suffer from severe infections and types of cancer. The infections and cancers are rare in those who have healthy immune systems.
HIV attacks a certain type of white blood cell, called a T lymphocyte. In addition to destroying T cells, HIV prevents the production of new T cells. Without these white blood cells, the immune system function is weakened greatly. The blood level of special T lymphocytes, called CD4 T lymphocytes, is low in those who have AIDS. The CD4 T lymphocyte count is less than 200 in people with AIDS.
Human Immunodeficiency Virus Origin
The exact origin of HIV is unknown, but it is suspected to have come from Africa. Studies suggest that chimpanzees, native to West Africa, were the origin of HIV. Experts feel that chimpanzees have harbored a similar virus, called SIVcpz for a few hundred thousand years. Unlike humans, infected animals do not develop AIDS from this virus. Transmission of the virus from the animal to the human population may have been through contaminated bites or scratches, or from eating these animals. At some point, the virus changed, or mutated, into HIV. The oldest case of HIV infection has been authenticated from a blood sample collected in 1959 from an African man.
Continue to Human Immunodeficiency Virus Transmission
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