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HIV and AIDS

Transmission Risk by Sexual Interaction

HIV infection is most commonly passed by sexual transmission. The most common ways it is passed is through vaginal or rectal intercourse. It is passed through oral sex as well.

Factors that Affect Transmission

The likelihood of transmission depends greatly on:

• The chance that a partner carries HIV
• The stage of that person's infection
• How high the viral load is of an HIV positive partner, but persons with very low or undetectable viral load can still transmit
• The presence or absence of other sexually transmitted diseases
• Douching, which increases the risk of transmission
• Correct and consistent condom use, which greatly decreases the risk of transmission

Transmission Risk by Sexual Activity

We have known since early in the epidemic that unprotected sex can transmit HIV. Worldwide most new infections result from sexual transmission, but not all sexual practices are equally likely to result in HIV transmission.

Each type of sexual activity has a different level of risk and certain sexual activities are more risky than others:

• Male-male insertive anal sex. Risk significant (1 in 500-1000 chance)
• Male-male/female receptive anal sex. Risk highest (1 in 200-500 chance)
• Male-female insertive vaginal sex. Risk significant (1 in 500 chance)
• Female-male receptive vaginal sex. Risk significant (1 in 500-1000 chance)
• Male insertive oral sex. Risk unclear/worse if uncircumcised
• Male/Female receptive oral sex. Risk significant (1 in 1,000 or slightly more)

Important Notes

HIV is commonly transmitted sexually by penile-anal intercourse. The receptive partner (bottom) is at much more risk, but the insertive partner (person putting his penis into the anus) can also get infected.

HIV is commonly transmitted sexually by penile-vaginal intercourse. The female is at more risk, but the male partner also can get infected.

HIV can be transmitted by oral sex and constitutes a high risk when performed without protection.

To Learn More:

• HIV and AIDs Basics: Prevention and Risks
• HIV in Infants and Children
• Preventing Mother-to-Child Transmission of HIV
• Women and HIV
• Symptoms and Warning Signs of HIV
• Getting Tested for HIV
• Types of HIV Tests
• HIV Test Sensitivity: False Negative and False Positive Results
• HIV Transmission and Oral Sex
• Your HIV Positive Partner and You
• Back to HIV and AIDs Overview

For more information:

Go to the HIV and AIDS health topic, where you can:

• Read articles on this topic
• Browse the previously asked questions
• Ask your own question.

This article is a NetWellness exclusive.

Last Reviewed: Sep 05, 2008

Carl Fichtenbaum, MD Associate Professor Division of Infectious Diseases Department of Internal Medicine College of Medicine University of Cincinnati

Pamposh Kaul, MD Assistant Professor Division of Infectious Diseases Department of Internal Medicine College of Medicine University of Cincinnati

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