Yes this is possible, and a lot of other people have been in the same situation.
You have just been very lucky.
The risk of catching HIV relates to many things, including your partners viral load (ie how infections he or she is).
In very early infection the risk could be a 1 in 10 per exposure or higher, but if it is very low or undetectable, this could drop to 1 in 3000 or less.
Depending on the type of sex you have, and how often, with these number you see how it could just be luck. You could still catch HIV the next time you are at risk. You should also have another HIV test in 3 months, to check that you were not infected in the few months prior to your original test.
A very small percentage of people (probably less than 2% in the UK), have genetic protection against HIV infection. There are no commercial tests that are able to check this.
While many people think (or hope) they have this protection, and that they will be lucky and not catch HIV if they don’t use a condom, in reality they are usually wrong. This is why numbers of new infections are still increasing each year.
Your partners diagnosis sounds like it was a shock for both of you. Take time to find good resources and support, both for your partner and yourself while you come to terms with what has happened. This affects people in all sorts of ways, but with good treatment and care, your partner can expect to lead a long life.
For more information on monitoring and treatment see the i-Base Introduction to combination therapy. Your partner may also want to call our phoneline.
Information on this website is provided by treatment advocates and offered as a guide only. Decisions about your treatment should always be taken in consultation with your doctor.