An infectious disease can be defined as an illness effecting a human or animal caused by a virus, bacteria, parasite or fungus. They can be spread by direct contact with an infected person or animal, ingesting contaminated food or water, contact with a vector, or contact with a contaminated surrounding such as animal droppings or air. .
As technology increases and researchers learn, treatment for many diseases is available. So one may ask, why do infectious diseases reemerge? The problem is that some microbes have evolved. They have demonstrated their outsmarting ability to adapt, survive and challenge us yet again. .
One such disease is Acquired Immuno-Deficiency Syndrome or AIDS/HIV. Last year alone, over forty million people were infected with AIDS and three million died. AIDS was introduced by a small group of rats that came to Italy abroad a traading ship from Turkey. Small Pox transmitted by trade goods from the Hudson Bay Company wiped out the entire Native American tribes. In the early 1980's , The Center for Disease Control and Prevention became aware that a new "virus" was effecting certain segments of society. In 1985, researchers isolated the virus that was being held responsible for AIDS. The definintion for the virus has changed many times, however the most recent definintion describes it as all HIV infected person who have a CD4 cell count of 200 cells per microleter of blood. In addition to laboratory evidence of an HIV infection coexisting with one or more disease indicators. .
HIV carries its genetic material in RNA rather than DNA, and while living in the host, the virus converts RNA to DNA in order to replicate. When seeking hosts, HIV is attracted to cells with CD4+ molecules on their surface such as T helper lymphocytes. HIV reproduces at an extremely fast rate which causes a large amount of damage to the host cells. Cell destruction grow geometrically as the virus replicates and seeks new cells to become its host.