Hesperian Health Guides

How HIV spreads

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HealthWiki > Helping Children Live with HIV > Chapter 7: Prevention of HIV in children and mothers > How HIV spreads

When people have HIV infection, the HIV virus lives in their blood and some of their other body fluids, such as semen, vaginal fluids, and breast milk. HIV spreads when these fluids get inside another person.

The ways people become infected with HIV are:

unsafe or unprotected sex with someone who has the virus. This is the most common way HIV spreads. To learn about safer sex, see How to prevent HIV with safer sex.
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HIV Ch7 Page 106-2.png for babies, during pregnancy, birth, or breastfeeding if the baby’s mother has HIV (mainly if she is not being treated with ART). HIV Ch7 Page 106-3.png
unclean or shared razors, needles, syringes, or any tool that pierces or cuts the skin. In some places, sharing syringes to inject drugs spreads as much HIV as sex does.
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blood transfusions, if the blood was not tested to be sure it is free from HIV. if HIV-infected blood gets into a cut or sore or open wound of another person.

HIV spreads more easily:

two women talk while a hidden woman listens and thinks
Soonyi was at the HIV clinic today. I knew her husband had AIDS!
How will I face those women now?
  • when fear of the stigma of HIV makes people avoid getting tested or treated.
  • when people with HIV do not get ART treatment, or they rely only on traditional medicines to “cure” HIV.
  • when people are pressured or forced to have unsafe sex.
  • when someone has sores on his or her genitals or inside the body. Sores allow HIV to get past the skin and deep into the body, where HIV infection happens. Both sexually transmitted infections (STIs) and schistosomiasis (bilharzia) cause sores inside the vagina. And dry, rough, or forced sex can tear the skin inside the vagina or anus.
  • when a person with HIV has a lot of HIV virus (called a high viral load) in each drop of blood. Right after being infected and later when he is very sick are the times when a person has the most HIV in his blood. Having another infection along with HIV, such as TB, an STI, or worms, also increases the amount of HIV in the blood.

HIV spreads less easily:

two sex workers talking to a man] near a sign that says "condoms required"
Sure mister, we have condoms here.
  • when people use condoms whenever they have sex, and feel more able to ask others to use condoms.
  • when people with HIV take ART each day, because this reduces the amount of HIV in their blood.
  • when people feel more able to talk about HIV, be tested, and know and disclose their HIV status to partners.
  • when people use only sterile needles to inject drugs.
  • when men are circumcised.
  • when people have sexual relationships with fewer people.

How HIV does not spread

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by touching, kissing, or hugging by sharing food, dishes, or utensils by sharing a bed
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by sharing or washing clothes, towels, bed covers, latrines, or toilets by caring for someone with HIV or AIDS from insect bites

Learn how to safely live with and care for someone with HIV or AIDS by reading Chapter 12: Common health problems.

two men talking
What about kissing? Can HIV spread through spit?
No. There is not enough HIV in saliva to infect someone. It is safe to kiss as long as neither of you has bleeding or sores in your mouth.

Avoid contact with blood to prevent spreading HIV

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HIV and many other illnesses can spread through unclean needles or tools that cut the skin. These can carry blood with HIV from one person’s body into another, and into the blood. Do not cut or pierce the skin with sharp objects, such as knives, blades, or needles, unless they are sterilized.

In general, avoid touching other people’s blood and body fluids. HIV can spread through blood in diarrhea and vomit. You might touch body fluids while caring for someone who is ill or for someone injured in an accident. Even if the person looks healthy, use gloves or a plastic bag to keep body fluids from getting on your skin, and try not to let fluids splash in your mouth or eyes. Keep any open wounds or sores on your skin covered to prevent contact with another person’s blood.

How to prevent HIV with safer sex

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Using condoms for safer sex can be a way of showing that you care about each other’s health.

HIV, like other sexually transmitted infections, spreads mainly through sex. This is because the moist, soft skin of the vagina, penis, anus, and mouth is torn easily or may have sores caused by infections or rubbing. Torn skin and sores are openings that allow germs or a virus like HIV to go deeper into a person’s body, into their blood where HIV infection happens.

When people have safer sex, it means they limit or avoid having their genitals touch skin to skin during sex. So the genital fluids that carry HIV — semen and vaginal fluid — do not touch the areas that can allow HIV into the other person’s body — the vagina, penis, anus or mouth. Using condoms is a good way to have safer sex.

If you or your partner have tested positive for HIV, or have more than one sex partner, or do not know your HIV status, safer sex can help you prevent HIV from spreading.

a chart showing risk of different kinds of sex

Safer sex works because HIV spreads less easily or not at all with some kinds of sex...
...and more easily with other kinds of sex.
  • kissing or touching
  • mutual masturbation (genitals not close)
  • watching videos
  • sex using a male or female condom
  • sex without ejaculation, “pulling out”
  • using any birth control during sex that does not include a condom
  • oral sex (mouth on penis or vagina)
  • sex in the anus without a condom
  • sex in the vagina without a condom
  • having many different sexual partners, or a partner with many different sexual partners
  • sex when the vagina or anus is dry

Other ways that can make sex safer are having fewer sexual partners, being tested for HIV before you have sex with any new partner (and asking them to be tested too), using lubricants for sex and avoiding dry sex, having sex without penetration, and treating any sexually transmitted infections quickly. “Dry” sex and forced sex cause torn skin, and many infections cause sores on or in the genitals, so these all help HIV spread. Also, men who are circumcised do not become infected with HIV as easily as uncircumcised men.

If you and your partner are both HIV-negative and have sex with no one but each other, you can have any type of sex you both like, and you need not worry about getting HIV from sex.

a teacher talking to a group of young people
What else can they do if a boy does not want to use a condom?
Is oral sex safer?
He could use thigh sex.
What is thigh sex?
They can use their hands.
a teacher talking to a young person
Thigh sex is when a boy rubs his penis between a girl’s thighs, well away from her genitals. In my grandmother’s time, this was allowed
Why can some boys control their urges and other boys seem unable to?

Encourage young people to use safer sex

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The way we raise our children can help protect mothers and babies from HIV. When we treat boys and girls more equally from birth, we prevent HIV — and many other problems — by:

  • helping girls stay in school.
  • helping all children, both girls and boys, develop their abilities, confidence, and sense of worthiness.
  • teaching both boys and girls to respect their bodies, and also to respect each person’s right to decide when and how to have sex.
  • protecting all children from violence and abuse, and helping them heal if they are abused.

Girls and boys can better avoid getting or spreading HIV if they postpone sex and wait to have babies until they are grown and have finished secondary school.

a man and a woman talking
Yonas has offered a large dowry to marry Zeina, but she is just 12 years old.
Zeina should finish school before we talk with her about marriage, don’t you think?

Sex and childbirth are both more dangerous for a girl who is not fully grown. Girls and young women more easily become infected with HIV and other STIs during sex because the skin inside their genitals is more likely to tear before they are fully grown. Also, if their partners are older men, these men are more likely to have HIV because they may have already had other partners.

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A girl who is not fully grown may have more difficult births because her pelvis is too small for the baby to pass through. This may make her bleed more, endangering the girl’s life and making it easier for HIV to spread to her baby.

Enabling young women and men to use family planning, including condoms, will both prevent unwanted pregnancies and prevent HIV. Working together as parents, teachers, health workers, and religious and community leaders can lead us to find ways to help young people avoid early sex, unwanted pregnancies, and HIV.

This page was updated:27 Nov 2019