Assessing HIV Risk

Anal Intercourse

Anal intercourse carries the highest sexual risk of HIV transmission because the lining of the rectum is particularly susceptible to microscopic injury.

Estimated risks per exposure:

• Receptive anal intercourse: approximately 1 in 90
• Receptive anal intercourse with ejaculation: approximately 1 in 65
• Receptive anal intercourse without ejaculation: approximately 1 in 170
• Insertive anal intercourse: approximately 1 in 170
• Insertive anal intercourse (uncircumcised): approximately 1 in 161
• Insertive anal intercourse (circumcised): approximately 1 in 909

These figures are averages and individual risk varies considerably depending on viral load, condom use, presence of other sexually transmitted infections and use of PrEP.

Oral Sex

Oral sex is one of the most misunderstood aspects of HIV medicine.

Many patients are surprised to learn that HIV transmission through oral sex appears to be extremely uncommon.

Estimated risks:

• Receptive oral sex (giving fellatio): less than 1 in 10,000
• Insertive oral sex (receiving fellatio): less than 1 in 10,000
• Semen splash to the eye: less than 1 in 10,000

Whilst these risks are extremely low, individual circumstances should always be considered.

Why These Numbers Need Context

One of the biggest mistakes people make is focusing solely on the type of exposure whilst ignoring the source.

The actual risk depends upon:

• Whether the source partner has HIV
• Whether they are receiving treatment
• Their viral load
• Whether PrEP was being taken
• Whether a condom was used
• Presence of other sexually transmitted infections

For example, receptive anal intercourse with a partner who has untreated HIV carries a very different risk from receptive anal intercourse with a partner who has a sustained undetectable viral load.

This is why personalised risk assessment remains far more useful than relying solely on published statistics.