Acquired Immunodeficiency Syndrome
Acquired Immune Deficiency Syndrome (usually referred to as AIDS) is a collection of uncurable diseases and symptoms often believed to be caused by long-term infection with the Human Immunodeficiency Virus.
- CD4 count less than 200 or
- CD4 percentage less than 14% of total lymphocytes or
- Any of the following illnesses: pulmonary TB, recurrent pneumonia, invasive cervical cancer.
- Expanded definition including 23 clinical conditions published elsewhere
The World Health Organization uses a different staging method for HIV disease. 
The illness was first recognized in the early 1980s as homosexual men presented to their doctors with a rare lung disease called Pneumocystis carinii pneumonia (PCP). Early on, the "gay disease" took on a variety of names, including "gay cancer" and "Gay-related immune deficiency" (GRID). However, when it was discovered that AIDS did not only occure in homosexual men, these gradually fell out of use. The Centers for Disease Control noticed an increase in requests for drugs needed to treat this illness and launched an epidemiological investigation.
Although the first cases of the disease probably go back to the 1950s, the epidemic was not recognized until the early 1980s . The early epidemic occurred in two main branches; in the US and other developed countries, and in sub-Saharan Africa. In the US, the early epidemic was primarily spread by homosexual sex, intravenous drug use, and blood transfusions (prior to the introduction of testing). In Africa, transmission was almost exclusively by heterosexual sex. Currently, most new infections worldwide are spread by promiscuous heterosexual sex and prostitution.
"We owe it to Ryan to make sure that the fear and ignorance that chased him from his home and his school will be eliminated. We owe it to Ryan to open our hearts and our minds to those with AIDS. We owe it to Ryan to be compassionate, caring and tolerant toward those with AIDS, their families and friends. It's the disease that's frightening, not the people who have it." —Former U.S. President Ronald Reagan, April 11, 1990 in regards to the case of Ryan White.
After infection with HIV, the virus quickly replicates in lymphatic tissue and travels through the blood to infect most areas of the body. The largest consequence of this is the "hijacking" of certain immune cells, especially so-called T-Helper, or CD-4, cells. Early in the infection, the immune system holds the infection at bay, often causing "Acute Retroviral Syndrome", a flu-like illness. Patients often have swollen lymph nodes. After approximately 8-10 years of infection, the immune system begins to lose its battle. This is primarily seen in the loss of numbers of CD4 cells, however the changes are somewhat more complex. When the CD4 cell level drops low enough, AIDS becomes apparent. The first symptoms of the illness are generally night sweats, weight loss, and oral thrush.
Opportunistic Infections (OIs)
The hallmark of AIDS is the appearance of opportunistic infections, meaning infections with organisms that do not usually cause human disease, unless given the right "opportunity". This opportunity is the reduction in cell-mediated immunity, first seen in patients with certain cancers or on anti-rejection drugs for organ transplantation. These infections include:
- Pneumocystis jiroveci, previously Pneumocystis carinii
- Candida albicans (the cause of thrush and vaginal yeast infections)
- Staphylococcus aureus (primarily causes skin infections)
- Toxoplasma gondii
- Streptococcus pneumoniae (the primary cause of pneumonia in AIDS patients)
- Mycobacterium tuberculosis (TB)
- Mycobacterium avium complex (atypical mycobacterium)
- Cryptococcus neoformans (a cause of meningitis)
- Epstein Barr virus (leads to a type of lymphoma)
- Human herpesvirus-8 (causes Kaposi's sarcoma)
Among the world's medical professionals and biologists, there is general agreement that HIV causes AIDS. In this, Koch's postulates have been clearly fulfilled, and basic science research has shown the same. Specific drugs have been developed that treat HIV infection and AIDS, helping show the causal relationship. That being said, there is a vocal minority of people, scientists and non-scientists alike, who do not believe that HIV causes AIDS. Foremost among these is Dr. Peter Duesberg. Details about these "re-thinkers" and their arguments can be found at several websites, but not in any reliable peer-reviewed journals: 
- http://www.merckmedicus.com/ppdocs/us/hcp/content/merck/hiv/hivaids/aidsdefi.htmAIDS is defined
- New England Journal of Medicine, Volume 344:1764-1772 June 7, 2001 Number 23
- Pneumocystis pneumonia -- Los Angeles. MMWR Morb Mortal Wkly Rep 1981;30:250-252)
- Some Questions the Media Won't Ask Today About AIDS, Robert Knight, NewsBusters, December 1, 2007