With the widespread use of anti-HIV drugs in many parts of the world, and the accompanying problem of drug resistance, it's become more common for people who contract HIV to be infected with a drug resistant strain. This can happen either through sexual transmission, through contact with infected blood (e.g. through injecting drugs), or from an HIV-positive mother to her baby.

Becoming infected with a drug resistant strain may seriously limit your treatment options in the same way as developing resistance while taking treatments, narrowing down the range of drugs which you might benefit from.

In the UK, about 10% of people newly infected with HIV have drug resistant virus. With time, and the greater use of multiple classes of HIV drugs, the transmission of HIV which is multi-drug resistant (resistant to a number of drugs and therefore more difficult to treat), is becoming more common not just in the UK, but also in Europe and north America.

It is becoming clear that somebody who is already HIV-positive can be re-infected with a drug resistant strain. This is called superinfection. It is not known how common this is, but so far it appears to be rare, and only 30 or so cases from around the world have been recorded. If you would like to discuss any concerns you may have about this, such as how it might affect your sexual behaviour, a health adviser at your HIV treatment centre or another member of your healthcare team should be able to help. You can also read more about superinfection in the NAM booklet in this series, HIV and Sex.