What Causes HIV?

Human immunodeficiency virus (HIV) causes include HIV-1 and HIV-2. Both viruses target and destroy CD4 cells, a type of white blood cell in the immune system. Compromised CD4 cells can result from untreated HIV, meaning your immune system becomes weaker over time.

Some, but not all, bodily fluids can play a role in the transmission of HIV. HIV can also be transmitted from a parent to a child in some situations, but children cannot inherit the condition. Anyone can get HIV, but certain behaviors may increase your risk of developing HIV. Read on to learn more.

HIV-1

HIV-1 is a type of retrovirus that is responsible for the majority of HIV infections around the world—around 95% of infections. There are also four groups of HIV-1 virus strains named M, O, N, and P; group M has nine strain subtypes. Acquired immunodeficiency syndrome (AIDS) is a more likely outcome of HIV-1 in terms of HIV infection progression.

HIV-2

HIV-2 is another retrovirus that can cause HIV. This virus typically causes West African cases of HIV infections. Other than being an uncommon cause of HIV, this version of the virus has a slower progression and is usually less aggressive than HIV-1. HIV-2 also has eight groups, A to H, with A and B being the groups that can lead to epidemics.

Is HIV Hereditary?

HIV is not a hereditary health condition. For a health condition to be hereditary, the condition has to pass from the parent to the child through the genes in sperm and egg cells.

It's still important to note that a birthing parent can transmit HIV to their child. This is known as vertical or perinatal transmission. Perinatal transmission can happen during pregnancy, childbirth, and breastfeeding or chestfeeding. 

Thanks to HIV and pregnancy guidelines and treatment options, there has been a decline in perinatal HIV transmission. These guidelines and options have played a role in making children less likely to get the virus from their birthing parent.

How Is HIV Transmitted?

HIV is transmitted when bodily fluids that contain the virus come into contact with your body’s tissue, blood, or broken skin (e.g., open wounds). The bodily fluids that can carry HIV are:

• Blood
• Breast milk
• Rectal fluids
• Semen and pre-seminal fluid
  
• Vaginal fluids
  

You can get HIV or transmit HIV to someone else through unprotected vaginal or anal sex and sharing needles, syringes, or other injection-related equipment. Though less common, a birthing parent who is HIV-positive can transmit HIV to their baby.

Although society has made a lot of progress in being educated about HIV, some harmful myths still exist about what body fluids or behaviors can transmit HIV. It is important to note that not all bodily fluids transmit the virus.

HIV cannot be transmitted through saliva, sweat, urine, or tears. You also cannot get HIV or transmit HIV to someone else through:

• Shaking hands, hugging, or other forms of casual contact
• Sharing eating utensils, towels, or bedding 
• Swimming in a pool
• Sitting on a toilet seat
  

Who Gets HIV?

Anyone can get HIV regardless of their age, race, ethnicity, gender, sex, sexual orientation, or geographic location. The number of HIV cases is highest in groups that share common risk factors. HIV is more common in:

• Men who have sex with men
• Transgender people, specifically trans women who have sex with men
• Black and Latino people
• People who test positive for another sexually transmitted infection (STI)
• People who use intravenous drugs or share needles
• Sex workers
  

Risk Factors

Certain behaviors increase a person’s risk of getting HIV. These risk factors include:

• Unprotected anal sex: The receptive partner (bottom) is at an increased risk of HIV transmission than the insertive partner (top) because the lining of the rectum is thin and prone to tearing. HIV can enter through these tears and make contact with open wounds and blood. The insertive partner is still at risk, however. HIV can enter the body through small cuts or open sores on the penis or through the opening at the tip of the penis, known as the urethra. 
• Unprotected vaginal sex: Vaginal fluid and semen both can carry HIV. The virus can enter the body through the tissue that lines the vagina, cervix, penis, and urethra. Although both partners are at risk of getting HIV, the receptive partner may have a greater risk than the insertive partner.
• Sharing needles: There is an increased risk of getting HIV when sharing needles, syringes, and other drug injection equipment with someone who is living with HIV. These objects may contain another person’s blood. People who inject drugs might also engage in other behaviors that increase their risk of HIV transmission—such as having unprotected sex.

A Quick Review

HIV is a virus that targets and destroys CD4 cells and weakens the immune system. If left untreated, HIV can lead to AIDS. You can get HIV or transmit HIV from person to person through blood, semen, rectal fluids, vaginal fluids, and breast milk. 

Specific behaviors like unprotected sex or sharing of needles and syringes can increase a person’s risk of getting HIV. Practicing safe sex and using clean needles can help lower your risk of acquiring the virus.