Estimated Hiv Transmission Risk Per Exposure
The estimates below should not be considered definitive but rather serve as a means to understand the relative risk of HIV by exposure type. The numbers are based on a meta-analysis of several large-scale studies which looked specifically at per-exposure risk.
| Exposure | |
| Mother-to-child, on ART with undetectable viral load | 0.1% |
Chances Of Getting Hiv From One Encounter
by Dr. Sanjiv Khanse | Diseases and Conditions
You have unprotected sex with someone from the opposite sex, just that once.
You realize later that the person is HIV positive, meaning that he/she is infected with the HIV .
You want to know what are the odds of you getting infected from exposure with that single unprotected encounter.
You could also have a blood transfusion once or share an injection needle with an infected partner just that once. What are the chances of contracting this viral disease?
The odds vary and depend on a few factors.
The Risk Of Acquiring Specific Stds From One Instance Of Unprotected Sex
| Disease | |
|---|---|
| 0.05â0.1% or 4 per 10,000 sexual acts | Receptive sex 1.4% or 138 per 10,000 |
| Insertive sex 0.06% – 0,16% or 11 per 10,000 sexual acts | |
| Herpes |
The risk of acquiring specific STDs from one instance of protected homosexual sex. 6,7
| Disease | |
|---|---|
| Low-Moderate if the lesions are covered by a condom | |
| High if the lesions are not covered | |
| Gonorrhea | |
| Low-Moderate if the ulcer is covered by a condom | |
| High if the ulcer is not covered | |
| HPV | Low-Moderate if the infective surface is covered by a condom |
| High if the infective surface is not covered |
Condoms are highly effective in protecting against HIV, gonorrhea, and chlamydia . Condoms are somewhat protective against HPV, syphilis, and herpes, which can be transmitted through skin-to-skin contact. If you want to practice âsafe sexâ, we do encourage you to use condoms.
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Measures You Might Think Are Helpful Immediately After Unprotected Sex
Unfortunately, doing these things does not prevent STDs:
- Washing the penis
- Douching
- Urinating after intercourse
These will help prevent urinary tract infections only. There is no evidence suggesting that cleaning your genitals with alcohol can be useful in preventing STDs. Moreover, overly active rubbing may irritate your skin and increase the risk of STD acquisition.
Risk Of Hiv Infection Per Single Sexual Exposure To An Individual Living With Hiv And Other Life Events With Comparable Risk Of Occurrence The Center For Hiv Law And Policy
Much of the discrimination that PLWH experience — from the workplace to the many criminal laws that target them — is based on a gross misunderstanding of the actual routes and statistical likelihood of HIV transmission. There is a broad lack of understanding that, even without effective antiretroviral treatment that reduces the level of HIV virus in the system and consequently the risk of transmission, most sex with a person who has HIV does not result in transmission to their partner.
This chart summarizes estimates on the actual per-act risk of HIV transmission through different types of sexual contact — e.g., receptive and insertive vaginal or anal sex — and then lists the risk of injury through life events that have a similar risk of occurring.
We created this short document to illustrate the fact that HIV is in fact a difficult virus to transmit, and to increase understanding of actual HIV transmission risks by comparing them to life events that cause immediate harm or death and pose a similar likelihood of happening.
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How Hiv Infects The Body
HIV infects the immune system, causing progressive damage and eventually making it unable to fight off infections.
The virus attaches itself to immune system cells called CD4 lymphocyte cells, which protect the body against various bacteria, viruses and other germs.
Once attached, it enters the CD4 cells and uses it to make thousands of copies of itself. These copies then leave the CD4 cells, killing them in the process.
This process continues until eventually the number of CD4 cells, also called your CD4 count, drops so low that your immune system stops working.
This process may take up to 10 years, during which time you’ll feel and appear well.
Page last reviewed: 22 April 2021 Next review due: 22 April 2024
No 2 Having Anal Sex : 1 In 72
The receptive partner is 13 times more likely to be infected with HIV than the insertive partner, according to the CDC. Thats because the virus found in blood, semen, preseminal fluid , and rectal fluids can more easily enter the receptive persons body through the thin lining of the rectum.
- Reduce the risk. If the insertive partner has HIV, using a condom during receptive anal sex can help reduce the risk of transmission by an average of 72 percent, according to the CDC. Water- or silicone-based lubricants can help lessen the chance that the condom will break.
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Reducing Your Personal Hiv Risk
The purpose of understanding relative risk is to establish the means by which to reduce your personal risk of infection or the risk of transmitting HIV to others. Oftentimes, it takes little to mitigate risk. For example, the consistent use of condoms correlates to a 20-fold decrease in HIV risk, while choosing insertive fellatio over insertive anal sex results in a 13-fold decrease. Conversely, the presence of an STI or genital ulcer increases the risk of HIV by anywhere from 200% to 400%.
Arguably the most important factor in assessing the likelihood of HIV transmission is the infected person’s viral load. Data suggests that the risk of an HIV-infected person with an undetectable viral load transmitting the virus is essentially zero.
The strategy called treatment as prevention strongly supports the use of antiretroviral therapy to reduce the infectivity of a person with HIV. It also reinforces the need for early testing to mitigate risk in mixed-status couples.
Knowing your serostatus and that of your partner allows you to make an informed choice on how to better protect yourselveswhether it be to abstain from high-risk activities, use condoms, or explore pre-exposure prophylaxis as a means to reduce the HIV-negative partner’s susceptibility to infection.
How Do You Get Or Transmit Hiv
You can only get HIV by coming into direct contact with certain body fluids from a person with HIV who has a detectable viral load. These fluids are:
- Blood
- Semen and pre-seminal fluid
- Rectal fluids
- Vaginal fluids
- Breast milk
For transmission to occur, the HIV in these fluids must get into the bloodstream of an HIV-negative person through a mucous membrane open cuts or sores or by direct injection.
People with HIV who take HIV medicine daily as prescribed and get and keep an undetectable viral load have effectively no risk of sexually transmitting HIV to their HIV-negative partners.
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Chances Of Getting An Std From Oral
Various STDS are able to spread through oral sex just as they can through vaginal intercourse and through anal sex. There can be increased risk if you dont use protection during oral sex, even if you do use them during other types of sex. Since pregnancy wont happen by oral sex and people may find it more pleasurable without protection, it may be likely that you wouldnt use protection during this type of sexual act. But the lack of protection makes you more vulnerable to contracting STDs.
Its possible to get an STD of the mouth or throat from oral sex or to spread an STD from the mouth or throat to the genitals, rectum or anus, but it depends on the type of STD as to how it can spread and where in your body you can get it. You could also have an STD that shows itself both on the mouth/throat area and the genital area.
Its hard to know whether your odds are higher with oral or penetrative sex. Thats because there havent been many studies on it and because people often have both types of sex, so its hard to separate them. Its best to assume that you could get an STD from any type of sexual contact, which is true. When any type of sexual contact is unprotected, the risk is higher.
You have an STD oral sex risk from these STDs:
- Herpes
- Trichomoniasis
- Syphilis
Its also possible to get hepatitis A from oral sex, and this infection is sometimes considered an STD because it can be spread through sexual contact as well as through other means.
Chlamydia Gonorrhea And Trichomoniasis Can Be Prevented With A Single Recommended Regimen
For chlamydia, gonorrhea, and trichomoniasis prevention, this approved antimicrobial drug combination is used:
A single dose of ceftriaxone plus a single dose of azithromycin plus a single dose of metronidazole OR a single dose of tinidazole .8 Ceftriaxone is used for gonorrhea prophylaxis, whereas azithromycin is effective against chlamydia. Metronidazole or tinidazole is used for trichomoniasis treatment. Metronidazole has common side effects, such as nausea, vomiting, and diarrhea. Ceftriaxone can be effective against syphilis in the incubation phase. 9
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How Hiv Is Transmitted
HIV is not passed on easily from one person to another. The virus does not spread through the air like cold and flu viruses.
HIV lives in the blood and in some body fluids. To get HIV, 1 of these fluids from someone with HIV has to get into your blood.
The body fluids that contain enough HIV to infect someone are:
- semen
- vaginal fluids, including menstrual blood
- breast milk
- contact with animals or insects like mosquitoes
Hiv Transmission Can Occur After Only One Exposure
Assigning an actual percentage to the “riskiness” of a certain activity is a tricky business. While statistics may suggest that there is only a 1-in-200 chance of getting infected by such-and-such activity, that doesn’t mean you cant get infected after only one exposure.
Instead, a 0.5% “per exposure” risk is meant to indicate that an average of one infection will occur out of 200 people who engage in a particular activity. It doesn’t mean that you need to do something 200 times in order to get infected.
It’s important to remember that risk estimates are based on two factors and two factors alonethat one person has HIV and the other doesn’t. Additional co-factors, such as co-existing sexually transmitted infections , general health, and the infected person’s viral load, can further compound risk until a low-risk activity is suddenly considerably higher.
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Is It Ok To Switch Between Daily Prep And On
On-demand PrEP is only for cis-gender MSM. Other individuals are not eligible for on-demand PrEP because studies have not demonstrated that it is effective for other populations. Before switching from daily PrEP to on-demand PrEP, or vice versa, a cis-gender MSM should consult with their healthcare provider.
Hiv Treatment As Prevention
People with HIV can take ART to lower their chance of transmitting HIV to others.
ART reduces the quantity of HIV in the body, or viral load, and keeps it at a low level.
The term viral load refers to the number of HIV copies per milliliter of blood.
Healthcare professionals define successful viral suppression as having a viral load of less than of HIV per milliliter of blood. Achieving and maintaining viral suppression significantly reduces the risk of HIV transmission.
Other ways to prevent HIV transmission include:
- using a condom or other barrier method during sex
- reducing the number of sexual partners
- getting vaccinated against other STIs, such as HPV and hepatitis B
- avoiding using injectable drugs, if possible
- if using injectable drugs, avoiding sharing needles and syringes
- following all workplace safety protocols
People can speak with a doctor to learn more about their individual risk of contracting HIV.
Anyone concerned about HIV exposure should contact a healthcare professional or a local emergency room to get testedand receive PEP.
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Is The Prep Medication Effective For Treating Hiv Infection
PrEP medications are not effective alone for treating HIV infection. If you acquire HIV infection while taking PrEP, the provider who conducted the HIV test should either provide HIV medical care or refer you to a healthcare provider who can provide HIV care. The HIV care provider will conduct lab tests and determine the most effective regimen to treat your HIV infection. There is no evidence that having taken PrEP will impact the effectiveness of your HIV treatment. People who acquire HIV while on PrEP can be successfully treated with HIV medications.
I Prefer Sex Without A Condom So I Don’t Always Use Them Would Prep Still Work To Prevent Hiv If I Don’t Use Condoms
If a person takes the PrEP medication consistently as directed, it provides a high level of protection against HIV. Condoms provide protection against sexually transmitted infections . People who are on the PrEP medication but are not using condoms may be exposed to an STI. It is important to be aware that having an STI can increase a persons chance of getting HIV if exposed to the virus. Some STIs dont have symptoms or symptoms may disappear on their own for periods of time. If you are not using condoms regularly, it would be especially important to have regular testing for STIs and to get treated as soon as possible if you have an STI. Screening for chlamydia and gonorrhea should include swabs of a persons genitals, rectum and mouth. Learning about the signs and symptoms of STIs is helpful in identifying whether you or one of your partners has an STI. Condom use is recommended but choosing to not use condoms routinely should not prevent you from being prescribed PrEP.
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How Would I Know If Prep Is Right For Me
PrEP is one of many options for preventing HIV. HIV is passed from one person to another through sharing injection drug equipment or through anal or vaginal sexual intercourse. People can avoid getting HIV by: 1) not sharing drug injection equipment , 2) avoiding anal or vaginal intercourse 3) having only one monogamous sex partner whose HIV status is known to be negative: 4) having only one partner who is living with HIV and has an undetectable viral load. It is important to be aware that a person living with HIV who is on HIV treatment and is virally suppressed for six months or longer cannot pass HIV to a partner through sex. If you have sex with more than one partner, taking PrEP or consistent and correct use of condoms each time you have sex, can prevent you from getting HIV.
New York HIV State Clinical Guidelines indicate that healthcare providers should discuss PrEP as an HIV/STD prevention option for adults or adolescents who:
It is important to weigh the pros and cons and have an open and honest conversation about PrEP with your healthcare provider before beginning PrEP. PrEP is always voluntary and only you can determine if PrEP is right for you.
Mother To Child Transmission
Having HIV does not mean a woman cant have a healthy baby. The key is to work with a doctor to take all the necessary precautions.
Aside from blood and sexual secretions, HIV can also be transmitted during pregnancy or through breast milk while breastfeeding. Mother to child transmissions can also occur at any point during pregnancy, as well as during delivery.
All pregnant women should be screened for HIV. Antiretroviral therapy is strongly recommended for pregnant women with HIV to achieve viral suppression. This will subsequently reduce the risk of transmitting HIV to the baby during pregnancy and labor. Sometimes a caesarean delivery is recommended to reduce transmission during delivery if the infection is not suppressed.
Its also important to protect the baby after birth. Breastfeeding might not be recommended in some cases, though consistent viral suppression may reduce the transmission of HIV through breast milk. A doctor may also recommend that the baby take antiretroviral therapy for up to six weeks after birth.
Overall, great strides have been made in decreasing HIV transmission between mothers and infants due to improved screening and use of anti-HIV drugs during pregnancy.
In the United States, the
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Multiple Vulnerabilities Increase Risk In Men And Women
Vaginal sex is one of the primary ways a person can become infected with HIV. According to the U.S. Department of Health & Human Services, it accounts for about 6,300 new infections among women each year in the U.S. and about 2,800 new infections among heterosexual men.
Globally, the figures are even more dismaying. While the sexual transmission of HIV in the U.S. is highest among gay and bisexual men , heterosexuals are by far the group most affected worldwide.
This is especially true in Africa where most new infections are among heterosexuals. In these populations, vaginal sex is the predominant route of infection.
I Have Sex Partners Who Are Living With Hiv And Have An Undetectable Viral Load Because They Are On Hiv Treatment Do I Still Need To Take Prep
Individuals living with HIV who are taking HIV treatment consistently and have an undetectable viral load for at least 6 months cannot transmit the virus to an HIV-negative partner through sexual activity. In sero-discordant or magnetic couples , PrEP may be used by the HIV-negative partner for additional protection.
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