through mucous membranes or blood-to-blood contact -- HIV infects the CD4+T cells and begins to replicate rapidly.
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.
What is 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.
What are CD4+T cells?
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.
How is HIV transmitted?
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.
The only way to determine HIV infection is to be tested for the virus. It is not unusual for HIV-infected persons to experience symptoms years after the initial infection; some may be symptom free for over 10 years. However, during the asymptomatic period, the virus is actively multiplying and destroying cells in the immune system, weakening the body's ability to fight infection. The effect is most keenly observed in the decline of the immune system's key infection fighters in the blood, the CD4+T cells. There are medical treatments that can reduce the rate at which HIV disables the immune system; early detection offers more options for treatment and preventative care. As a matter of safety, people who engage in high-risk behaviors -- such as intravenous drug use or having unprotected sex with multiple partners -- should be tested regularly.
How can I lower my risk of HIV infection?
Practicing safe sex and avoiding high-risk behaviors are the keys to protecting yourself from HIV. This begins with understanding that there is a risk of transmission any time infected blood, semen, vaginal secretions or breast milk are exchanged. By limiting the possibility of these fluids entering your bloodstream, you are lowering the possibility of HIV infection. You can achieve this by limiting the number of people you have sex with, never sharing needles with anyone at any time and avoiding the use of alcohol or drugs before having sex. Drugs and alcohol may influence your decision and may reduce your ability to practice safer sex.
Safe sex involves using a latex condom or latex square (dental dam) for sexual activities -- when used properly, latex is an effective barrier against the spread of HIV. In addition, the use of lubricants should be limited to water-based only, as oil-based lubricants can break down latex condoms within seconds of use.
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