HIV testing and risks of sexual transmission

This guide to HIV testing and HIV transmission was updated in December 2019.

Main changes since the previous edition are based on:

• U=U: how an undetectable viral load on ART stops HIV transmission, and
• PrEP: how effectively PrEP also prevents transmission.

This guide was produce to answer all questions on transmission risk and HIV testing.

Introduction

HIV in the UK

HIV basics

• HIV, sex and risk
• Which body fluids are infectious?
• What are the routes of infection?

Ways that HIV is not transmitted

Risks for transmission

• Between 100% safety and 100% risk
• You and your partners HIV status
• Viral load
• Type of sex and condom use
• Oral sex
• Sexual fluid
• How long sex lasts
• How vigorous the sex is
• Genetics
• Medical male circumcision
• Other sexually transmitted infections (STIs)
• Luck (and statistics)

HIV testing: feelings of fear, anxiety and guilt

Frequently Asked Questions (FAQs)

• Do I have HIV or need to test?
• Symptoms and seroconversion
• Does washing after sex increase the risk? (maybe, yes)
• How can my partner test positive and I test negative?
• Are some people protected from infection?
• Risks for men vs women and insertive vs receptive?

PrEP (Pre-Exposure Prophylaxis)

PEP and PEPSE

U=U: Undetectable = Untransmittable

HIV testing

• How soon can I take a test?
• What is the window period?
• Where can I test in the UK?
• Why do some UK clinics ask people to wait 3 months?
• What happens when I test?
• How long do results take and how are they reported?
• What does a number on my negative HIV test result mean?
• Test accuracy, results and further testing
• What happens after my test?
• What happens if I am HIV positive?

Skin, mucous membranes and HIV transmission

Timeline for immune responses and testing

Additional sections

• Appendix 1: Different types of HIV test
• Appendix 2: Theoretical risk, population risk & individual risk
• Appendix 3: How HIV tests work

Glossary

Further information and links

References

PDF

Feedback

Tables, diagrams and illustrations

Credits

This guide was written and compiled by Simon Collins for HIV i-Base with appendices written by Charlotte Walker.

First edition February 2012.
Second edition February 2013.
Third edition July 2016.

Thanks to the community and healthcare professional advisors for comments including Dr David Asboe, Bisi Alimi, Polly Clayden, Paul Clift, Nathan Geffen, Li Marhaban, Angelina Namiba, Emma Rezel, Memory Sachikonye, Tracy Swan, Matt Williams.

Thanks to Monument Trust and MAC AIDS Fund for supporting this publication.

About our guides

Information about how we produced this guide and the importance of using language that is direct and easy to understand.

This includes information on how to write non technical medical information that may be useful as a resource for other organisations.

Cover: Untitled, 1984 © Keith Haring Foundation. Used with permission.

Last updated: 1 December 2019.