HIV
HIV is a virus that damages the immune system. Untreated HIV affects and kills CD4 cells, which are a type of immune cell called T cell.

Over time, as HIV kills more CD4 cells, the body is more likely to get various types of conditions and cancers.

HIV is transmitted through bodily fluids that include:

• blood
• semen
• vaginal and rectal fluids
• breast milk

The virus isn’t transferred in air or water, or through casual contact.

Because HIV inserts itself into the DNA of cells, it’s a lifelong condition and currently, there’s no drug that eliminates HIV from the body, although many scientists are working to find one.

However, with medical care, including a treatment called antiretroviral therapy, it’s possible to manage HIV and live with the virus for many years. Without treatment, a person with HIV will likely develop a severe condition called Acquired Immunodeficiency Syndrome, known as AIDS. At that point, the immune system is too weak to respond to other diseases, infections, and conditions successfully.

Untreated, life expectancy with end-stage AIDS is about 3 years trusted Source. With antiretroviral therapy, HIV can be well-managed, and life expectancy can be nearly the same as someone who has not contracted HIV. The human immunodeficiency viruses (HIV) are two species of Lentivirus (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive. Without treatment, the average survival time after infection with HIV is estimated to be 9 to 11 years, depending on the HIV subtype. In most cases, HIV is a sexually transmitted infection and occurs by contact with or transfer of blood, pre-ejaculate, semen, and vaginal fluids. Non-sexual transmission can occur from an infected mother to her infant during pregnancy, during childbirth by exposure to her blood or vaginal fluid, and through breast milk. Within these bodily fluids, HIV is present as both free virus particles and virus within infected immune cells.

 Research has shown (for both same-sex and opposite-sex couples) that HIV is untransmittable through condomless sexual intercourse if the HIV-positive partner has a consistently undetectable viral load.