What Causes HIV?

HIV transmission occurs through certain bodily fluids. Unprotected sex and sharing needles are the primary risk factors for getting the virus.

Human immunodeficiency virus (HIV) is a virus that targets and destroys CD4 cells—a type of white blood cell. Your immune system uses white blood cells to fight off infections. If HIV is left untreated, CD4 cells can become compromised, causing your immune system to become weaker.

The more your condition progresses, the harder it is for your body to fight illnesses and infections. Understanding the causes and risk factors of this condition may help you prevent the onset of the virus and its symptoms. 

HIV is transmitted person to person via certain some (but not all) bodily fluids. Anyone can get HIV, but certain behaviors may increase your risk of developing the condition.  

two men sharing bed

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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:

You can get HIV or give 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 

Is HIV Hereditary?

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. Because of this, HIV is not a hereditary health condition.

However, it’s 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 breast/chestfeeding. 

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

Who Gets HIV?

Anyone can get HIV regardless of their age, race, ethnicity, gender, sex, sexual orientation, or geographic location. 

But 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
  • 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 getting HIV 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 for getting HIV—such as having unprotected sex.

Needle Exchange Programs

Needle exchange programs (NEPs) help people who use injection drugs to get clean needles for free or at a very low cost. NEPs can help prevent the spread of HIV. To find a NEP near you, you can visit the North American Syringe Exchange Network here.

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. 

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7 Sources
Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. About HIV/AIDS.

  2. Centers for Disease Control and Prevention. Ways HIV can be transmitted.

  3. World Health Organization. HIV

  4. National Cancer Institute. Hereditary.

  5. HIV.gov. Can a pregnant person transmit HIV to their baby?

  6. HIV.gov. Who is at risk for HIV?

  7. Centers for Disease Control and Prevention. Factors that increase HIV risk

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