HIV is short for Human Immunodeficiency Virus, which is the virus that causes AIDS. This virus is passed from one person to another through blood-to-blood and/or sexual contact. In addition, infected pregnant women can pass HIV to their baby during pregnancy or delivery, as well as through breast-feeding.
Because tattooing, piercing, scarification, and most other forms of body modification involve blood, HIV is a very real risk. It takes relatively little infected blood to infect a healthy individual. That said, in comparison to other bloodborne pathogens, HIV is a very fragile one — realistically your odds of catching HIV via a sloppy body modification studio are not that high. You are far more likely to be exposed to Hepatitis, which is much more resilient and can survive longer in hostile environments. Hepatitis C is just as fatal.
HIV is most prominent in blood and ejaculate (female and male), however it is also present in negligible quantities in other bodily fluids. Though present in saliva, scientific tests have determined that saliva has natural properties that restrict HIV's ability to be transmitted successfully through this fluid (but piercers should take the risk seriously in the case of a needle stick injury while doing an oral piercing). Tears have tested positive for HIV, however scientists have found no evidence that HIV can be spread through tears (tears are often present after a septum piercing or nostril piercing). HIV is not present in urine, feces, sweat, or vomit.
HIV is often referred to as an infection (HIV infection) but is called the AIDS virus in the later stages. HIV infects the cells of the immune system, which is the body's defense against germs. As a result of their HIV infection, most HIV positive people will eventually develop AIDS.
HIV is known as a lentivirus (lenti = slow). The course of infection with these virii are characterized by a long interval between initial infection and the onset of serious symptoms. This is why someone can get infected with HIV and only have it show up in tests many years later. Because of this latency, it is very important that people at risk of contracting the virus be tested every year — including not only body modification practitioners but those who receive body modifications.
HIV belongs to a class of viruses called retroviruses. Retroviruses are ribonucleic acid (RNA) viruses, and in order to replicate they must make a deoxyribonucleic acid (DNA) copy of their RNA. The DNA genes allow the virus to replicate. Viruses are limited in where they can successfully replicate — they can only do so within a host cell — they do this by assuming control of the cells manufacturing structures forcing them to work only on replication of the virus. Though all viruses use that method of reproduction, only retroviruses, once inside a cell, use an enzyme called reverse transcriptase to convert their RNA into DNA, which can be incorporated into the host cell's genes. Once this happens the cell is permanently viral — this is the reason why there is no cure for HIV or AIDS.
How can you help prevent the spread of HIV? Get tested every year, only go to reputable piercers and studios, avoid piercing guns, don't share blood products or hypodermic supplies with anyone, don't attempt to pierce/tattoo/scar anyone without proper training, and practice safe sex. There are over 15,000 new HIV cases every day — don't be one of them.