Terrence Higgins Trust and CHAPS have launched the facts-based programme, Biology of Transmission, looking at the factors involved in the transmission of HIV during unprotected anal sex.

Information posters and credit cards will be out in services and venues in Sheffield over the next couple of weeks. Further information and resources are available from the THT website www.chapsonline.org.uk/biology

This campaign will focuss on three main points; anal absorbancy, rectal damage and sexually transmitted infections.

Anal Absorbancy

One of the reasons unprotected anal intercourse is such an effective mode of HIV transmission is due to the high absorbancy of the rectal lining. Semen can become absorbed into the blood stream through the rectal lining - taking HIV with it.

 Damage from anal 'play'

On top of high absorbancy, cuts caused by intercourse, fingers, hands and sex toys can further increase transmission routes during unprotected anal intercourse. Used properly, condoms can greatly reduce the risk of HIV being passed on if the rectal lining has been damaged.

Sexually Transmitted Infections

Sexually transmitted infections (STIs), can cause ulcers and other damage to the lining of the rectum. This provides similar transmission routes to those created from anal play. Regular sexual health screening will detect and treat these STIs, reducing the risk of transmission via damage to the rectal lining.

For more information, visit the THT website www.chapsonline.org.uk/biology

To arrange a Sexual Health Screening appointment at the Department of Genito-Urinary Medicine at the Royal Hallamshire Hospital in Sheffield tel: 0114 276 6928; or to find your local Sexual Health Clinic contact NHS Direct on tel: 0845 46 47