HIV Prevention: What People With HIV Need to Know

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There is a whole range of ways in which you can lower the risk of passing on HIV while still having pleasurable sex.

It is important to know that -- in biological terms -- HIV is not a virus that transmits easily. It is not passed on during each and every sexual act. In fact, more often than not, HIV is not passed on, even when no form of protection has been used.

"Safer sex" is often defined as any kind of sex that avoids body fluids getting into the bloodstream of another person -- so that definition would include the use of barrier methods as well as sex that isn't penetrative. But that idea of safer sex seems pretty limited now that antiretroviral drugs can make those same body fluids uninfectious.

Male condoms provide a physical barrier. "Female" condoms do the same but give the bottom/receptive sex partner more control. But these days, there is much more to HIV prevention than condoms:

Taking antiretroviral drugs often means that there's virtually no HIV in your body fluids, making transmission likely impossible.

If your HIV-negative partner takes antiretrovirals as pre-exposure prophylaxis (PrEP), it almost completely eliminates any risk of HIV taking hold in his or her body. This is true whether or not you are taking antiretroviral drugs yourself.

And choosing to have sex only with other people living with HIV completely cuts out any risk of HIV transmission.

Undetectable Viral Load in HIV-Positive People

The most important thing for anyone to understand about HIV prevention today is that sex with an HIV-positive person who has an undetectable viral load is safer sex. If your HIV treatment is working well, then the sex you have is protected sex.

Antiretroviral drugs, when taken by a person living with HIV, can stop the virus from infecting new cells and replicating. In most cases, the quantity of HIV in body fluids falls dramatically -- so much so that the viral load test result comes back with the result "undetectable." As there is hardly any HIV in semen, vaginal moisture and other body fluids, your chance of transmitting the virus is close to or likely zero, even if these fluids get into your partner's body. In fact, as of the date of this article, there hasn't been a single transmission from an undetectable partner in more than 58,000 condomless sex acts, according to the largest study on this subject.

A few exceptions and qualifications: You can only count on this protection after your viral load has been undetectable for a full six months. Good adherence to your treatment, without missing doses of your pills, is vital. If either partner has an untreated STI (such as chlamydia or gonorrhea), the risk of transmission may be a little raised.

And speaking of STIs, it's worth remembering that HIV treatment won't do anything to protect you from a partner's STI. Male and female condoms are much better for that. You can easily combine condoms and an undetectable viral load, providing strong all-around protection.

If you're looking to have a child with an HIV-negative partner, an undetectable viral load could help you to conceive safely.

If you want to involve your partner in decisions about safer sex, one challenge can be that most people who don't have HIV have no idea what an undetectable viral load is. Equally, it is rarely recognized by legal authorities as a means of preventing HIV transmission. Many U.S. states have archaic legislation criminalizing behavior that might expose another person to the risk of HIV transmission when disclosure of HIV status has not taken place or cannot be proven. A number of people who had an undetectable viral load and who did not transmit HIV have been jailed.

PrEP Use by HIV-Negative Partners

Rather than the person with HIV taking antiretrovirals, another option is for your HIV-negative partner to do so. This is known as pre-exposure prophylaxis (PrEP).

PrEP is highly effective, as long as the drugs are taken regularly, as directed. It takes seven days to have effective levels of protection for anal receptive sex and 21 days for the receptive partner in vaginal sex. It works for men and women, heterosexual and gay.

The CDC's mathematical models indicate that PrEP makes penetrative sex about ten times less risky than it would otherwise be. Combining PrEP with condoms can make sex between 30 and 50 times less risky. Combining PrEP with HIV treatment lowers the risk by at least 250 times.

Like HIV treatment, PrEP can't provide any protection against other STIs.

"Male" Condoms Worn by the Penetrative Partner

Condoms are cheap and readily available. Used carefully and consistently, condoms are effective against HIV -- as well as other STIs and unwanted pregnancy.

Make sure you follow the advice about correctly using condoms -- use one that is the right size, use water or silicone-based lubricant, and so on. Otherwise the condom may break or slip off.

For most forms of penetrative sex, the CDC says that condoms reduce the risk of HIV being passed on by about five times. For anal sex with the HIV-positive partner taking the insertive ("top") role, condoms reduce the risk by about three times. Combining condoms with one of the other prevention methods described in this article increases the level of protection.

Unlike the antiretroviral methods we've already discussed, condoms need to be thought about and put on in the heat of the moment, at the time of having sex. That requires the agreement or tacit acceptance of both partners.

"Female" Condoms Worn by the Receptive Partner

The qualities and effectiveness of so-called female condoms are pretty similar to those of male condoms. They were designed to be put on by the receptive partner in vaginal sex, potentially giving that partner more power to protect herself -- especially if the insertive partner is unwilling to use a male condom. Some people, including gay men, have found that they can also be used for anal sex.

Obviously, their look and feel is different. At first this can be surprising -- it's worth trying them a few times before deciding whether you like them or not. Couples who find male condoms uncomfortable or difficult to use may find that they prefer female condoms.


One way to eliminate your risk of passing on HIV is to have sex with someone who is also living with HIV.

Even if you don't actively seek out other positive people as partners, if your next partner turns out to also have HIV, there's no need to worry about HIV being passed on.

Some people say that condomless sex with another person with HIV could result in super-infection with a different strain of HIV -- perhaps one with resistance to some anti-HIV drugs. But in practice, this hasn't turned out to be a problem causing difficulties for many people.

What you are more likely to pick up is an STI. For example, dense networks of HIV-positive gay men having condomless sex with multiple partners tend to favor STI transmission. Along with easily treated infections such as gonorrhea and syphilis, this can also involve more serious infections such as hepatitis C.

Choosing Your Position

If you're an HIV-positive gay man having anal sex with an HIV-negative man, it's useful to know that your taking the receptive ("bottom") role will always be less risky for your partner than your taking the insertive ("top") role.

Non-Penetrative Sex

Finally, let's not forget the many ways you can be sexual without penetration. Even without HIV treatment, oral sex is very low risk, even if it's not possible to prove that it's zero risk in every case. There's virtually no risk of HIV transmission in kissing, touching, massage or mutual masturbation, and these activities should be considered safe.

Putting a Number on It

Remember, HIV is not passed on during each and every sexual act. In fact, more often than not, HIV is not passed on, even when no form of protection has been used.

But if you're wondering what the chances are of passing on HIV during sex with an HIV-negative person, the Centers for Disease Control and Prevention (CDC) has published an informative online calculator -- the Risk Reduction Tool -- that you may wish to use. This tool is the source of all the numerical estimates in this article.

The online tool asks you to specify the sexual activity, each partner's HIV status and a few other variables.

Let's take as an example, vaginal sex, with the male partner having HIV but taking HIV treatment and neither partner having a sexually transmitted infection (STI).

The CDC tool tells us that HIV could be passed on less than 0.5 times in every 10,000 sex acts. That's a scientist and statistician's way of saying the risk is close to zero -- they can't exclude the possibility of a transmission happening one day, but it'll be a one-off.

You can play around with the tool, adjusting details to see how the risk changes. You'll see that if the HIV-positive partner wasn't on treatment, the risk of HIV transmission would be about 25 times greater. Using a condom also cuts the risk of HIV being passed on -- but not as much as HIV treatment does. Combining condoms and HIV treatment provides the greatest protection.

You can also see things that make HIV transmission more likely, such as having an STI. And if the HIV-positive partner acquired HIV only in the past month, then the risk of passing on HIV is seven times greater. This is because viral loads are much higher in the early phase of HIV infection. If the couple were having anal rather than vaginal sex, the risk would also be greater.

The tool makes it clear: the anxiety some people living with HIV feel about the likelihood of passing on HIV is exaggerated. Even one of the riskier acts -- anal sex without a condom with an HIV-positive man who is not on HIV treatment taking the insertive ("top") role -- is estimated to result in HIV transmission 138 times in every 10,000 sex acts. Put in another way, that's a 1-in-72 chance.

Consult the CDC's Risk Reduction Tool here.