Human immunodeficiency virus (HIV) targets CD4 cells, a type of white blood cell, and destroys them. CD4 cells play an important role in fighting infections in the body. Without treatment, HIV disrupts the function of CD4 cells and weakens the immune system. The more severe the virus is in the body, the more difficult it becomes to fight diseases and infections. Therefore, understanding the causes and risk factors of HIV can help in preventing the spread of the virus and its symptoms.

HIV is transmitted when a body containing the virus comes into direct contact with body tissues, blood, or damaged skin, such as open wounds. Body fluids that can carry the HIV virus include breast milk, vaginal fluids, rectal fluids, blood, and pre-seminal fluid. HIV transmission can occur through sexual intercourse and sharing of needles or other equipment involved in injection. An HIV-positive mother has a high risk of transmitting the virus to her baby during childbirth. It is important to note that HIV cannot be transmitted through saliva, urine, tears, or sweat.

In principle, anyone is at risk of contracting HIV regardless of age, gender, sexual orientation, race, or other diversities. However, most cases of HIV occur within groups with similar risk factors. Groups vulnerable to HIV may include transgender individuals, men who have sex with men, sex workers, black and Latin individuals, drug users who share needles, as well as people who have been diagnosed with other sexually transmitted infections.

The translated text while preserving the HTML tags is as follows: The behaviors include: 1. Sharing needles, which increases the risk of HIV transmission because the equipment may be contaminated with blood from another individual. 2. Engaging in vaginal sex without a condom, as vaginal fluids and semen can contain the HIV virus. In this situation, the partner receiving penetration may have a higher risk than the partner performing penetration. 3. Engaging in anal sex without a condom, as HIV can enter the body through open wounds or small cuts. The partner receiving penetration has a higher risk of infection than the partner performing penetration.