HIV Transmission and Risk: Separating Fact From Fiction

It’s much harder to transmit HIV than most people think. Thanks to years of dedicated work by scientists and researchers, we now have a solid understanding of the way HIV passes from person to person.

Unfortunately, much of our society is still clinging to harmful, outdated myths about HIV transmission.

In a recent survey, 28% of millennials and Gen Zers said they would be reluctant to hug, talk to, or even associate with someone living with HIV—despite the fact that none of those behaviors pose any risk.

Thankfully, we have good science to combat misinformation about the way HIV passes from one person to another. In this resource guide, we’ll break down the science of HIV transmission and dispel harmful misconceptions. We’ll also explain why certain groups of people are more likely to be living with HIV than others, and we’ll offer practical steps you can take to keep yourself HIV negative—or, if you’re living with HIV, to prevent onward transmission of the virus.

If you’re reading this guide because you were recently diagnosed with HIV, remember that you will be OK. Powerful medicines can help you live a long and healthy life. When it comes to HIV transmission, you shouldn’t be afraid to hug, kiss, and touch your loved ones. You will not hurt them.

If you are HIV negative but worried about becoming HIV positive, there are steps you can take to protect yourself when you have sex, or if you inject drugs. But don’t be afraid to hug, kiss, and touch your friends and loved ones living with HIV. They deserve your love and affection.

Where Did Myths About HIV Come From?

The early 1980s were a scary time for people living with HIV. By the spring of 1983, scientists had identified the virus responsible for a mysterious illness called acquired immune deficiency syndrome (AIDS), but they didn’t understand how it passed from person to person.

Initially, some researchers speculated this new infection could be passed through casual contact or even through the air, like tuberculosis. Others theorized it might be hitching a ride with mosquitoes or other insects, like malaria.

By the end of 1983, experts already knew better, and the Centers for Disease Control and Prevention (CDC) tried to put those misguided early theories to rest. They announced that the virus that causes AIDS was most likely “transmitted sexually or, less commonly, through contaminated needles or blood,” and not “through food, water, air, or environmental surfaces.”

But the damage had already been done. Myths about HIV transmission had already taken root, and these myths continue to make life difficult for the 1.1 million people living with HIV today in the United States.

Today we have a solid scientific understanding of HIV transmission. We know that HIV can only be transmitted in very limited circumstances, such as sexual contact or needle sharing. And we have a much better understanding of the way that viral load—that is, the amount of HIV in a person’s bloodstream—influences their chances of passing on the virus.

You can use this information to educate yourself, your friends, and your community about the real risk of HIV transmission.

How Does HIV Work?

The full scientific name for HIV is human immunodeficiency virus. It’s an infection that attacks the immune system, and it operates like this:

• The virus itself is shaped like a bowling ball covered in tiny spikes
• After HIV enters the bloodstream, it uses those tiny spikes to latch on to white blood cells (also called CD4 cells), the body’s first line of defense against infections
• As soon as HIV gets inside white blood cells, it uses the cell’s own machinery to create copies of itself, creating effective camouflage that tricks the immune system into leaving it alone
• As HIV creates even more copies of itself, it hijacks a person’s immune system
• A weakened immune system means that people living with untreated HIV may start to get all sorts of infections that would never normally make them sick Eventually, without proper treatment, HIV leads to AIDS and becomes life-threatening

Today’s anti-HIV medicines have been designed to address each stage of the infection process.

Some of these medications, which are also called antiretrovirals, stop HIV’s spikes from latching on to CD4 cells. Others use different methods to stop HIV from replicating.

These drugs can’t completely eradicate the virus from a person’s body, but they do successfully stifle its ability to make copies of itself.

Here’s where it’s important to break down the concept of viral load. Remember, viral load is a measure of how much HIV is inside a person’s bloodstream. For people living with HIV, this means that the more virus in your blood, the more likely it is you may pass HIV to somebody else if other forms of protection aren’t used. By taking anti-HIV medications, you will not only see your personal health improve, but you will reduce the chances of passing the virus along.

How Does HIV Get Inside the Body in the First Place?

It turns out that it’s relatively difficult for HIV to get inside the body and lock on to those white blood cells. This can only happen during intimate contact between two people—by which we mean anal sex, vaginal sex, or sharing injection-drug equipment.

HIV cannot pass through a person’s skin. This means that you will not become positive by touching bodily fluid that contains HIV, unless you have an open wound where you’re touching the fluid. Even if you ingest the virus—let’s say, by eating food with traces of HIV inside it—the acid inside your stomach will protect you.

HIV almost always enters the body in one of three ways:

• Direct contact with the bloodstream, either through an open wound or with a needle.
• Direct contact with certain mucous membranes—specifically, the soft, permeable tissues inside the rectum, vagina, penis, and mouth. For newborns, exposure is possible during pregnancy, delivery, or shortly after birth by consuming breast milk from an HIV-positive person.

For adults, it’s important to remember that HIV can only enter the body when it’s exposed to an open wound, injected directly into the bloodstream, or passed through a mucous membrane, typically through anal or vaginal sex.

In addition, anyone who is pregnant should get an HIV test. If the results come back positive, your doctor can help you stay healthy and prevent your baby from getting HIV.

Which Bodily Fluids Can Pass HIV?

“Bodily fluid” is a blanket term that refers to any of the liquids floating around inside the human body. We’re talking blood, sweat, tears, semen, vaginal fluids, urine, and all the rest.

HIV does not spread throughout the body evenly. Some bodily fluids have it, but most don’t. In fact, HIV can only be transmitted to another person through these three types of bodily fluids:

• blood
• sexual fluid (including semen, vaginal fluid, and rectal fluid)
• breast milk

That’s it.

HIV cannot be passed from person to person via other fluids like tears, saliva, vomit, or feces. This is an incredibly important point about HIV transmission that is often misunderstood.

For decades—and still today—people have worried they might catch HIV from a toilet seat, perhaps by touching the urine or fecal matter of an HIV-positive person. This absolutely does not happen.

People have also worried they might catch the virus from the saliva of an HIV-positive person who kisses them or spits on them. In fact, this fear is so pervasive that some states have made it a felony for people with HIV to spit at or bite someone else. Those laws are based on outdated science.

The only way it would be possible to transmit HIV through saliva is if the HIV-positive person had bleeding gums or sores, and somehow that bloody saliva got into the bloodstream of the HIV-negative person. However, experts agree that the risk of this happening is so statistically tiny that it’s not worth worrying about.

So, to recap:

• Among adults, the virus’s most likely entry route inside the body is through blood-to-blood contact, or by an exchange of sexual fluids.
• Among newborns, HIV can be transmitted by HIV-positive people during pregnancy, delivery, or breastfeeding. (Collectively, this is called, “perinatal transmission”; the word perinatal means before, during, or right after birth.)

Next, we’ll break down the most common ways HIV is transmitted.

This video on HIV risk and casual contact, featuring David Malebranche, M.D., is part of the #AskTheHIVDoc series by Greater Than AIDS, a public outreach program run by the Kaiser Family Foundation.

How Is HIV Usually Passed From One Person to Another?

In the United States, most people who become HIV positive are exposed to the virus in one of four ways:

• sex
• sharing injection needles
• mother-to-child transmission
• accidental needle-stick injury (e.g., by a hospital worker)

Let’s break these down a little further:

Sex and HIV

The most common way that HIV is transmitted from one person to another is through condomless penetrative sex. In fact, the majority of new HIV infections among young adults in the United States happen this way.

Among all the different types of sex that people can have, here’s how the most common rank in order of HIV risk, assuming no forms of protection are used and the person living with HIV has a detectable viral load:

1. receptive anal sex (bottoming): 1.4% per act
2. penetrative anal sex (topping): 0.1% per act
3. receptive penis-to-vagina sex: 0.08% per act
4. penetrative penis-to-vagina sex: 0.04% per act

Anal receptive sex (bottoming) carries the highest risk: According to estimates from the CDC, HIV will be transmitted in 138 out of every 10,000 of these acts, assuming no other protective measures have been taken. That translates to a risk of 1.4% per act.

An HIV-negative person who engages in condomless anal penetrative sex (topping) can also acquire HIV; it’s just technically not as risky as bottoming. The CDC estimates the risk at 11 transmissions per 10,000 acts, or 0.1% per act.

Penetrative penis-to-vagina sex is also a typical method for HIV to pass from person to person. Although it’s technically more risky for the person with the vagina (the receptive partner) than the person with the penis (the insertive partner), the overall risks are pretty low: 8 per 10,000 acts (.08%) for the receptive partner and 4 per 10,000 acts (.04%) for the insertive partner.

Drug Use and HIV

The second-most common way HIV is transmitted is when people share needles and other injection-drug equipment. Although the HIV virus can’t survive for long in the open air, it can stay alive inside a slim needle for more than a month.

Although the number of HIV infections due to shared injection-drug equipment is lower than the number of HIV infections due to sex, the risk is higher: According to the CDC, it’s around 63 transmissions per 10,000 acts, or 0.6%.

Pregnancy and HIV

HIV can also be transmitted to infants during pregnancy, labor, delivery, or after birth via breast milk. This is called mother-to-child or perinatal transmission. It’s very uncommon in the United States and other resource-rich countries, where routine testing and treatment standards have helped drastically curb infections.

Other Types of HIV Risks

Another less-common way HIV is transmitted in the United States is needlestick injury. This typically happens when a health care worker is accidentally jabbed by a used needle or syringe that contains HIV-positive blood. Again, this is very rare.

Thirty years ago, blood transfusions and organ donations were an especially dangerous way that some people acquired HIV. Nowadays, donated blood and organs are routinely tested.

How Is HIV Not Passed From One Person to Another?

You may have just read the section above and thought to yourself: Wait, that seems like a really short list of ways HIV gets transmitted. What about mosquitoes? Blowjobs? Kissing? Sharing food or utensils?

As we’ve previously discussed in this guide, there are a lot of myths and misconceptions about HIV transmission. At some point, people without HIV may worry they have been exposed to the virus. And when people get freaked out about their health, they tend to start scouring the internet for answers.

At TheBody, we’ve spent the past 25 years fielding questions about HIV exposure fears and talking with experts about the realities of HIV risk. So we know an awful lot about the HIV transmission concerns people tend to have in common.

These are the top five recurring fears about HIV transmission that are way, way more than they’re cracked up to be:

• oral sex
• kissing (or exchanging saliva)
• sharing food, drinks, or utensils
• erotic massage
• mosquitoes

Let’s break each of these down in more detail.

Oral Sex

Although HIV transmission during oral sex is technically possible, the CDC says there is “little to no risk.”

Here’s the deal: Because sexual fluid and blood both contain HIV, it is biologically possible to transmit the virus during oral sex if sores are present in the mouth or on the genitals, or if menstrual fluid is present.

That said, extremely few cases of probable HIV transmission through oral sex have been reported in the history of the epidemic, so to the best of our knowledge, it almost never occurs.

If we’re talking about theoretical risk, it may be higher for a person who uses their mouth to perform oral sex on a person’s penis. It also may be higher when either partner has another sexually transmitted infection (STI), such as chlamydia or syphilis.

You can further reduce already-low risks of HIV through oral sex by:

• Ensuring a condom is used.
• Ensuring that you don’t receive an ejaculation inside your mouth.

It’s also worth noting that, if a person with HIV is on treatment and their viral load is undetectable, they can’t transmit HIV during sex.

And if an HIV-negative person is taking a medication regimen called PrEP (short for pre-exposure prophylaxis), they’re also almost completely protected from infection.

Kissing

One of the biggest myths about HIV is that it can be transmitted by a kiss. There is virtually no chance HIV will ever be transmitted by a kiss, because the live virus is not present in saliva.

When it comes to kissing, HIV cannot be passed from person to person, whether it’s a chaste peck on the cheek or deeper, tongue-on-tongue action. The only way transmission becomes theoretically possible is if both partners have open wounds or sores inside their mouths, and blood is exchanged during a deep, open-mouth kiss. But experts say the risk of this happening is extremely low.

For similar reasons, this is why HIV also can’t be transmitted through a person being spit on.

Sharing Food, Drink, or Utensils

Speaking of mouths: Everything I just mentioned when explaining why kissing is not an HIV-transmission risk also applies to eating and drinking. That includes every type of normal food- or drink-sharing scenario you can think of, including splitting a plate of nachos, drinking from the same water bottle, and using the same fork when sharing a piece of cake.

The only documented cases of HIV transmission through food are extremely specific: They involve food that a person with HIV pre-chewed and then fed to an infant.

Needless to say, this is an extraordinarily rare event—only a few cases have ever been recorded—and they most likely involved blood entering the food due to the adult having poor oral hygiene.

So unless you’re making like a mama bird and its chick, you can enjoy a meal or a drink with a person who’s living with HIV and have zero concern that you’re putting yourself at risk.

Erotic Massage

HIV cannot be transmitted through non-penetrative sexual acts, such as massages, rubbing, or other romantic touches. This is true whether or not partners are fully clothed or completely naked.

HIV is not transmitted from skin-to-skin contact. Only the relatively thin tissues in a person’s rectum and vagina are vulnerable to HIV, and even then they would have to be directly exposed to the wet blood or sexual fluids of an HIV-positive person who does not have an undetectable viral load.

Mosquitoes

It is impossible to acquire HIV from a mosquito, tick, or other blood-sucking insect. This is true even if that insect just bit someone living with HIV.

The reason? These creatures don’t get HIV in the same way humans do. They simply are not the “host” the HIV virus is looking for, so insects themselves never become HIV positive. Instead, the blood they consume gets digested in their stomachs, along with the HIV.

Even if an insect bites an HIV-positive person and immediately afterward snacks on an HIV-negative person, it never transfers any of the blood from its previous meal into the new host.