Study Finds Drug-Resistant HIV in Half of Infected Patients

About half the people infected with the AIDS virus in the United States harbor a strain of the microbe that is resistant to at least one drug used to treat the disease, according to a new study. The findings, presented yesterday in Chicago at the American Society for Microbiology's annual meeting on infectious diseases, are the first national measurement of how widespread drug-resistant strains have become in the six years since combination therapy revolutionized HIV care.

The findings suggest that an unusually large number of people face the possibility that their HIV infections may become difficult to treat. In addition, an increasing fraction of newly infected patients may start out with a resistant microbe. While ominous, the prevalence of drug-resistant virus is a largely unavoidable price of the use of antiretroviral drugs, which have prolonged tens of thousands of lives.

"It's a wake-up call that we've created a lot of resistance with the use of our drugs, and that it's happened in a short period of time," said Douglas D. Richman, a physician at VA San Diego Healthcare System, who presented the study. While not in themselves more virulent, drug-resistant strains are generally more difficult and expensive to treat.

The project sampled about 2,000 HIV-infected people in 33 states, 30 cities and 50 rural areas whose care was provided by 58 major hospitals or organizations and 200 small clinics or individual practitioners. Among those alive in 1999 and under medical care, about 37 percent had no detectable HIV in their blood and presumably harbored no, or virtually no, resistant virus. The remaining 63 percent had detectable virus. These included people taking antiretroviral therapy, people who had taken it and stopped, and people who had never been treated. Of those with detectable virus, 78 percent carried a strain resistant to at least one drug. Overall, 49 percent of participants carried a drug-resistant strain. Numerous experts, however, doubt that drug-resistant strains will become dominant, because they must compete with "wild-type" strains that are more easily transmitted and more biologically fit.

Drug-resistant virus was seen most often in gay white men with good access to health care. This may be because middle-class gay men were the first to use antiretroviral drugs, either singly or in combinations. Use of medicines singly -- as was common in the late 1980s and early 1990s -- almost always leads to emergence of resistant HIV. Resistance was less common in those treated by physicians with many HIV patients, suggesting that a practitioner's experience and expertise are key to optimal HIV care. Richman said the findings suggest the need for greater use of new lab tests that allow physicians to identify drugs a patient is resistant to before beginning treatment.

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