More and more people in the UK are becoming infected with strains of HIV that are resistant to common drug treatments, warns a new report.
The UK Collaborative Group on Monitoring the Transmission of HV Drug Resistance studied a group of patients who had contracted HIV and had not started taking medication. It found that 27 per cent of patients tested in 2000 had viruses with drug-resistant mutations. This compares with 0 per cent of patients tested between 1994 and 1996.
Certain HIV drugs can still be used on these patients, but the treatment range available is reduced. Three per cent of the newly studied patients had strains of the virus resistant to the three major classes of HIV drugs.
The group warns that the problem is likely to get worse. Increasing numbers of people with HIV are taking highly active antiretroviral therapy. If they do not stick to the difficult drug regime, resistance to the drugs can develop. These drug resistant strains are then more likely to be passed on. The patients studied by the UK group had become infected with the drug-resistant strains by their partners.
Frank Maldarelli of the US National Cancer Institute’s HIV Drug Resistance Program in Maryland says the UK figure of 27 per is surprisingly high.
In the US, about 15 to 20 per cent of newly infected patients have drug-resistant strains of HIV. But this figure is rising, Maldarelli says. “I don’t think we’re in an epidemic range yet, but I don’t know how fast the increase will be,” he told New Scientist.
Viruses with many mutations are generally not very robust, and are less likely to survive. Some researchers hoped this would prevent drug-resistant strains of HIV from being widely transmitted. But Deenan Pillay, director of the Public Health Laboratory Service Antiviral Susceptibility Reference Unit in Birmingham, and lead author of the study, says the new research suggests this will not be the case.
The strains of HIV studied by the group had developed more mutations causing resistance to Zidovudine (AZT) than to any other drug. AZT was the first widely used HIV drug, and is often used to help prevent the transmission of HIV from a pregnant woman to her child.
The group also found mutations that convey resistance to another five drugs. Pillay thinks a larger study would find patients with strains of HIV resistant to all available drugs.
“There are three major classes of HIV drugs. Some people are showing resistance to all three, which of course is even more problematic,” says Gavin Hart from the National Aids Trust in London.
HIV drugs are given in very high, toxic doses on schedules that are difficult to follow – precisely in order to avoid resistance. But ironically, those difficult programmes could be adding to the problem of emerging drug resistance, since patients find it difficult to stick to the treatment course.
The authors add that prevention is still the best policy for combating HIV, and that safe sex needs to be encouraged throughout the world.
“This underlines the fact that prevention is our top priority,” says Hart.
More at: British Medical Journal (Vol 322, p 1087)