HIV is a virus that invades the body and attacks the immune system, according to WebMD. The immune system is the body's defense against infection. The immune system uses white blood cells to fight infection, and HIV destroys certain white blood cells, allowing infections to overtake the body.
Two types of HIV exist, and they are HIV-1, which is the most common cause of nearly all cases of AIDS worldwide, and HIV-2, which causes AIDS-like illnesses and is rare in North America. The HIV virus causes the HIV infection, and it is contracted through blood, semen or vaginal fluids, according to WebMD. Unprotected sex is the most common way that people become infected. Sharing drug needles with an HIV-positive person can transfer the virus between users. Moreover, the infection can be passed from a mother to her baby through breastfeeding, birth or pregnancy.
The disease goes through several stages, which include acute retrovirus syndrome, stage one, stage two and stage three, as explained by WebMD. As the disease progresses, it transforms into stage three, which is known as AIDS. The stage of the infection is determined by white blood cell count, and it can take up to 12 years for HIV to turn into AIDS, according to WebMD. A variety of medication therapies can slow down the progression of HIV.