Patients diagnosed with HIV may soon have to be routinely screened for resistance to some of the powerful drugs that have proved effective against the virus and Aids.
Researchers in the US have provided fresh evidence that new HIV strains are already becoming less susceptible to treatment by the cocktails of medicines developed over the past 10 years.
The potential for resistance, even among newly diagnosed patients who have never undergone treatment, displayed in recent scientific papers, was underlined by scientists working for the centres for disease control in Atlanta, Georgia. They discovered an HIV strain which appears to be becoming resistant to zidovudine, better known as AZT or Retrovir. It is one ingredient in the three-part drug cocktail most commonly used to fight the virus.
The researchers, reporting in the Proceedings of the National Academy of Sciences, screened for viral mutations in 603 recently diagnosed and untreated patients. They found 20 had HIV with a genetic alteration which gave it an increased ability to give rise to an AZT-resistant strain.
Scientists and Aids charities fear drug resistance could undermine recent advances in treatment. Deenan Pillay, of the public health laboratory service for England and Wales said the latest research strengthened the argument for screening.
At present screening in Britain is sometimes undertaken for newly infected patients. But it is rarely undertaken on those thought to have been carrying HIV for years. This is because any resistant strain may be hiding behind another "fitter" one and not show up in a test which can cost between £200 and £300.
However, the US work suggested that resistant strains left detectable markers and helps those arguing that routine screening for resistance would help ensure the right therapy from the start. Dr Pillay said: "You want to be sure it is hitting the virus hard and use the best combination of drugs from the word go."
There are about 15 drugs used to combat HIV and Aids, and the Terrence Higgins Trust said it was vital their power was protected for as long as possible. "This research clearly shows why we cannot afford to let up on our efforts to halt the spread of HIV. Combination drug therapies are powerless against emerging untreatable strains."
