HIV stands for human immunodeficiency virus. It is the virus that can lead to acquired immunodeficiency syndrome, or AIDS, if not treated. Unlike some other viruses, the human body can’t get rid of HIV completely, even with treatment. So once you get HIV, you have it for life.
HIV attacks the body’s immune system, specifically the CD4 cells (T cells), which help the immune system fight off infections. Untreated, HIV reduces the number of CD4 cells (T cells) in the body, making the person more likely to get other infections or infection-related cancers. Over time, HIV can destroy so many of these cells that the body can’t fight off infections and disease. These opportunistic infections or cancers take advantage of a very weak immune system and signal that the person has AIDS, the last stage of HIV infection.

-An estimated 21.7 million people were receiving HIV treatment in 2017. However, globally, only 59% of the 36.9 million people living with HIV in 2017 were receiving ART.
-As a result of recent advances in access to antiretroviral therapy (ART), HIV-positive people now live longer and healthier lives. In addition, it has been confirmed that ART prevents onward transmission of HIV.
-Globally, an estimated 36.9 million (31.1–43.9 million) people were living with HIV in 2017, and 1.8 million (1.3–2.4 million) of these were children. The vast majority of people living with HIV are in low- and middle-income countries. An estimated 1.8 million (1.4–2.4 million) people were newly infected with HIV in 2017. An estimated 35 million people have died from HIV-related causes so far, including 940 000 (670 000–1.3 million) in 2017.

https://aidsinfo.nih.gov/understanding-hiv-aids/fact-sheets/19/45/hiv-aids–the-basics
https://www.hiv.gov/hiv-basics/overview/about-hiv-and-aids/what-are-hiv-and-aids
http://www.who.int/news-room/facts-in-pictures/detail/hiv-aids