Only by funding tests will we learn how big a headache it is likely to be. He added that if the UK had similar figures to the US that could mean quite a few people were already resistant to treatment. And he warned that the percentage affected was likely to rise as drug-resistant strains were passed on, although drug companies are producing around two new drugs a year in an effort to keep ahead of the virus. Safer sex Mr Williams said the threat of drug resistance meant more efforts had to be put into safer sex messages and to supporting people taking their drugs. Failure to take the full course of anti-retroviral drugs or incorrect dosage is thought to be the reason for resistant strains of the virus emerging.
Experts say it drug regimes are hard to follow.
They often involve a lot of drugs which have to be taken daily for the rest of a person's life. Some have specific conditions attached to them, such as having to be taken at certain times of the day. THT has trained volunteers to help patients take their medication. The BBC is not responsible for the content of external internet sites Links to other Aids stories are at the foot of the page.