- The human immunodeficiency virus (HIV) is the virus that potentially causes AIDS (acquired immune deficiency syndrome). HIV primarily attacks the immune defense system, making the patient extremely vulnerable to opportunistic infections, which are infections that occur in people who have weakened immune systems.
- HIV primarily infects and destroys immune cells with the CD4 receptor protein on their cell surfaces (also called CD4-positive or CD4+ T-cells). Healthy individuals have a CD4 cell count between 600 and 1,200 cells per microliter of blood. HIV patients have less than 600 CD4 cells per microliter of blood.
- Patients progress to AIDS when/if their CD4 cell counts drop to lower than 200 cells per microliter (one-one millionth of a liter) of blood. This may happen if a person does not receive adequate treatment or if he/she develops a serious infection or illness. Individuals with a CD4 cell counts lower than 200 have the greatest risk of developing potentially fatal opportunistic infections, such as Mycobacterium avium complex (MAC) infections, because their immune systems are very weak.
- HIV is transmitted from person to person via bodily fluids, including blood, semen, vaginal secretions, and breast milk. Therefore, it can be transmitted through sexual contact with an infected person, by sharing needles/syringes with someone who is infected, through breastfeeding, during vaginal birth, or, less commonly, through transfusions with infected blood. However, in countries where blood is screened for HIV antibodies, HIV infection is rarely transmitted through blood transfusions. Very low amounts of HIV have been found in saliva and tears in some AIDS patients. However, contact with saliva, tears, or sweat has not been shown to result in HIV transmission.
- The most common type of HIV worldwide is called HIV-1. It is easily transmitted and is the cause of most HIV/AIDS infections around the world. HIV-1 has several subtypes (A through H and O), which are more common in certain parts of the world but produce AIDS similarly. The second type, called HIV-2, is much less common and less virulent or infectious.
- Since 1981, when the first case of AIDS was reported in the United States, the disease has become a global pandemic, causing an estimated 65 million infections and 25 million deaths worldwide.
- During the mid-to-late 1990s, advances in HIV treatment slowed the progression of HIV infection to AIDS. This consequently led to decreases in AIDS-related deaths. According to the U.S. Centers for Disease Control and Prevention (CDC), the number of AIDS-related deaths continues to decline, with an eight percent decrease from 2000 through 2004. However, the number of AIDS diagnoses increased eight percent during that period as well.
- From 2000 to 2004, the estimated number of people living with AIDS increased from 320,177 to 415,193, according to the CDC. This 30% increase can partially be attributed to advanced treatments that have helped HIV/AIDS patients to live longer lives, as well as increased access to testing and information about the disease.
- According to the CDC, an estimated 2.8 million patients died from AIDS, 4.1 million people became infected with HIV, and 38.6 million were living with HIV worldwide in 2005. According to the Joint United Nations Programme on HIV/AIDS (UNAIDS) and World Health Organization (WHO) 2006 AIDS Epidemic Update, an estimated 39.5 million people are currently living with HIV worldwide. It is also estimated that 4.3 million people became newly infected in 2006, with 2.8 million (65%) of these cases occurring in Sub-Saharan Africa. In 2006, 2.9 million people died from AIDS-related illnesses.
- Certain geographic regions, such as Sub-Saharan Africa and the Caribbean, have much higher rates of infection than others. Certain populations, such as Sub-Saharan women, men who have sex with men (MSM), prostitutes, and injection-drug users, are also at increased risk for HIV infection.
- Currently, there is no cure for HIV/AIDS. However, treatment with anti-HIV drugs, called antiretrovirals, may suppress the virus, which subsequently helps boost the immune system. Although these drugs may help patients live longer lives, they do not reduce the risk of transmitting the disease to someone else.