The Human Immunodeficiency Virus (HIV) is the virus that leads to AIDS. HIV belongs to a subset of retroviruses called lentiviruses (or slow viruses), which means that there is an interval -- sometimes years -- between the initial infection and the onset of symptoms. Upon entering the bloodstream -- through mucous membranes or blood-to-blood contact -- HIV infects the CD4+T cells and begins to replicate rapidly.
CD4+T cells are the immune system's key infection fighters and the entity that allows HIV to enter, attach and infect the body's immune system. The CD4+T cells (also called T4 cells) are disabled and destroyed by the virus, often with no symptoms, causing a significant decrease in the blood levels of T4 cells. In the advanced stages of HIV, the body may have fewer than 200 T4 cells, while a healthy adult's count is 1,000 or more. In this way, the body's immune system is continuously weakened from the moment of infection and the inability of the immune system to fight infection opens the door to opportunistic infections.
Scientists believe that when the virus enters the body, HIV begins to disable the body's immune system by using the body's aggressive immune responses to the virus to infect, replicate and kill immune system cells. Gradual deterioration of immune function and eventual destruction of lymphoid and immunologic organs is central to triggering the immunosuppression that leads to AIDS.
Acquired Immunodeficiency Syndrome (AIDS) is the final stage of HIV infection. The Centers for Disease Control establish the definition of AIDS, which occurs in HIV-infected persons with fewer than 200 CD4+T cells and/or persons with HIV who develop certain opportunistic infections. In 1992, the CDC redefined AIDS to include 26 CDC-defined AIDS indicator illnesses and clinical conditions that affect persons with advanced HIV.
An infection takes the "opportunity" provided by the weakened immune system to cause an illness that is usually controlled by a healthy immune system
HIV infection most commonly occurs through sexual contact. However, the virus can also be spread through blood-to-blood contact -- such as sharing needles or blood transfusions involving unscreened blood. Studies have shown that HIV is not transmitted through casual contact such as touching or sharing towels, bedding, utensils, telephones, swimming pools, or toilet seats. Scientists have also found no evidence of transmission through kissing, sweat, tears, urine or feces. It is important to acknowledge that it is not sex that transmits HIV, but certain bodily fluids: blood, semen (including "pre-cum"), vaginal secretions and breast milk. High-risk behaviors that can result in HIV transmission are sharing needles for drugs, tattoos, body piercing, vitamins or steroids with an HIV-infected person and/or engaging in unprotected anal, vaginal or oral sex with a person who is HIV infected. The virus also can be transmitted from an HIV-infected mother to her child through pregnancy, birth or breastfeeding.
It does appear that persons already infected with a sexually transmitted disease are more susceptible to acquiring HIV during sex with an infected partner. Mucous membranes, a weak point in the skin, include the lips, mouth, vagina, vulva, penis or rectum. Because mucous membranes are porous and viruses and other pathogens are able to pass through, these areas are rich in immune cells. When a person already has a sexually transmitted disease, sex organs may be flooded with CD4+T cells, making it much easier for HIV to infect.
According to the Centers for Disease Control and Prevention, the following are symptoms that may be warning signs of HIV infections:
�Rapid weight loss
�Dry cough
�Recurring fever or profuse night sweats
�Profound and unexplained fatigue
�Swollen lymph glands in the armpits, groin or neck
�Diarrhea that lasts for more than a week
�White spots or unusual blemishes on the tongue, in the mouth or in the throat
�Pneumonia
�Red, brown, pink or purplish blotches on or under the skin or inside the mouth, nose or eyelids
�Memory loss, depression and other neurological disorders
What is the distinction between HIV and AIDS?
AIDS is a disease developed by a person living with HIV, which is a viral organism. The term AIDS applies to the most advanced stages of HIV infection. Although an HIV-positive test result does not mean that a person has AIDS, most people will develop AIDS as a result of their HIV infection.