Genetics is also related to the risk of catching HIV. Some genes are protective and some genes increase the risk. The same genes affect how fast HIV progresses in an HIV positive person.

For example, a genetic mutation called a CCR5 delta-32 deletion, protects against some types of HIV. Less than 1% of people may have these genes but this is not something that is easy to test.

Tests are expensive and only available in research studies.

Also, up to 10% of new infections are with a type of HIV (called CXCR4) that overcomes this protection.

Most people who think they are protected because of their genetics have actually just been lucky.

Just as genetics can protect against infection, genetics can also increase the risk. You or your partner will have different genetics and this is not possible to test.

Although some viruses can be more infectious, individual immune responses have a bigger impact on HIV transmission.

You cannot change your genes (or your immune system) so this is both an unknown and fixed risk factor.

Last updated: 1 June 2016.