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Basic Questions and Answers About HIV Transmission

January 16, 2015

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Can I Get HIV From Oral Sex?

Yes, but most types of oral sex carry little to no risk of HIV.

Oral sex involves giving or receiving oral stimulation to the penis (fellatio), the vagina (cunnilingus), or the anus (anilingus or rimming). Most types of oral sex carry little to no risk of HIV. The highest oral sex risk is performing oral sex (fellatio) with ejaculation in your mouth. However, the risk is still low, and much lower than anal or vaginal sex. Factors that may increase the risk of transmitting HIV through oral sex are oral ulcers, bleeding gums, genital sores, and the presence of other sexually transmitted diseases (STDs) (which may or may not be visible). The risk is lower if the partners are using condoms or dental dams, if the partner with HIV is taking antiretroviral therapy (ART) consistently and correctly, and if the partner who is HIV-negative is taking pre-exposure prophylaxis (PrEP) consistently and correctly. Condoms and HIV medicines can greatly lower the risk of transmitting HIV.

For more information, see Oral Sex and HIV Risk.


Is There a Connection Between HIV and Other Sexually Transmitted Diseases?

Yes. Having a sexually transmitted disease (STD) can increase the risk of getting or spreading HIV.

If you are HIV-negative but have an STD, you are at least 2 to 5 times as likely to get HIV if you have unprotected sex with someone who has HIV. There are two ways that having an STD can increase the likelihood of getting HIV. If the STD causes irritation of the skin (e.g., from syphilis, herpes, or human papillomavirus), breaks or sores may make it easier for HIV to enter the body during sexual contact. Even STDs that cause no breaks or open sores (e.g., chlamydia, gonorrhea, trichomoniasis) can increase your risk by causing inflammation that increases the number of cells that can serve as targets for HIV.

If you are HIV-positive and also infected with another STD, you are 3 to 5 times as likely as other HIV-infected people to spread HIV through sexual contact. This appears to happen because there is an increased concentration of HIV in the semen and genital fluids of HIV-positive people who also are infected with another STD.

CDC recommends sexually active gay and bisexual men test for:

  • HIV.
  • Syphilis.
  • Hepatitis B and C.
  • Chlamydia and gonorrhea of the rectum if you've had receptive anal sex, or been a "bottom" in the past year.
  • Chlamydia and gonorrhea of the penis (urethra) if you have had insertive anal or oral sex in the past year.
  • Gonorrhea of the throat if you've performed oral sex (i.e., your mouth on your partner's penis, vagina, or anus) in the past year.

Sometimes your health care provider may suggest a herpes test.

For more information about the connection between HIV and other STDs, see the CDC fact sheet, The Role of STD Detection and Treatment in HIV Prevention. To get tested for HIV or other STDs, find a testing site near you.

Can I Get HIV From Someone Who Is Living With HIV But Has Undetectable Viral Load?

Yes. Even though having an undetectable viral load greatly lowers the chance that a person with HIV can transmit the virus to a partner, there is still some risk.

Viral load refers to the amount of HIV in the blood. An undetectable viral load is when the amount of HIV in the blood is so low that it can't be measured. Antiretroviral therapy (ART) reduces viral load, ideally to an undetectable level, when taken consistently and correctly. A person with HIV can still potentially transmit HIV to a partner even if they have an undetectable viral load, because

  • HIV may still be found in genital fluids (e.g., semen, vaginal fluids). The viral load test only measures virus in blood.
  • A person's viral load may go up between tests. When this happens, they may be more likely to transmit HIV to partners.
  • Sexually transmitted diseases (STDs) increase viral load in genital fluids.

Can I Get HIV From Injecting Drugs?

Yes. If you share injection drug equipment with someone who has HIV, your risk is high.

Risk also depends on whether the person who has HIV is using antiretroviral therapy (ART) consistently and correctly, and whether the person who is HIV-negative is using preexposure prophylaxis (PrEP) consistently and correctly.

Sharing drug equipment (or works) can also be a risk for spreading HIV. Infected blood can get into drug solutions by

  • Using blood-contaminated syringes to prepare drugs.
  • Reusing water.
  • Reusing bottle caps, spoons, or other containers (cookers) to dissolve drugs in water and to heat drug solutions.
  • Reusing small pieces of cotton or cigarette filters (cottons) to filter out particles that could block the needle.

"Street sellers" of syringes may repackage used syringes and sell them as sterile syringes. For this reason, people who continue to inject drugs should get syringes from reliable sources of sterile syringes, such as pharmacies or needle-exchange programs.

It is important to know that sharing a needle or syringe for any use, including skin popping and injecting steroids, hormones, or silicone, can put you at risk for HIV and other blood-borne infections.

Can I Get HIV From Using Other Kinds of Drugs?

Not directly, but being drunk or high affects your ability to make safe choices and lowers your inhibitions, which may lead you to take risks such as having sex without a condom.

Methamphetamine (meth) is a very addictive stimulant that can be snorted, smoked, or injected. Even though using meth is an HIV risk factor for anyone who does it, there is a strong link between meth use and HIV transmission for men who have sex with men (MSM). MSM who use meth may increase their sexual and drug-use risk factors. They may

  • Use condoms less often.
  • Have more sex partners and have sex over a longer period of time.
  • Engage in unprotected anal sex -- especially as the receptive partner.
  • Inject meth instead of smoking or snorting it.

Drinking alcohol, particularly binge drinking, and using "club drugs" like Ecstasy, ketamine, GHB, and poppers can alter your judgment and impair your decisions about sex or other drug use. You may be more likely to have unplanned and unprotected sex or use other drugs, including injection drugs or meth. Those behaviors can increase your risk of exposure to HIV. If you have HIV, this can also increase your risk of spreading HIV to others.Treatment programs can help people stop using drugs or alcohol. Find a treatment facility near you or call 1-800-662-HELP (1-800-662-4357).

If I Already Have HIV, Can I Get Another Kind of HIV?

Yes. This is called HIV superinfection. The new strain of HIV can replace the original strain or remain along with the original strain. The effects of superinfection differ from person to person. For some people, superinfection may cause them to get sicker faster because they become infected with a new strain of the virus that is resistant to the medicines they are currently taking to treat their original HIV infection. Research suggests that the kind of superinfection where a person becomes infected with a new strain of HIV that is hard to treat is rare, less than 4%.

Are Health Care Workers at Risk of Getting HIV on the Job?

The risk of health care workers being exposed to HIV on the job (occupational exposure) is very low, especially if they use protective practices and personal protective equipment to prevent HIV and other blood-borne infections. For health care workers on the job, the main risk of HIV transmission is through accidental injuries from needles and other sharp instruments that may be contaminated with the virus; however, even this risk is small. Scientists estimate that the risk of HIV infection from being stuck with a needle used on an HIV-infected person is less than 1%.

For more information on preventing occupational exposure to HIV, see the CDC fact sheet, Occupational HIV Transmission and Prevention Among Health Care Workers.

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This article was provided by U.S. Centers for Disease Control and Prevention. Visit the CDC's website to find out more about their activities, publications and services.