More Than 40% of HIV-Positive Individuals in San Francisco Will Have Drug-Resistant Viral Strains by 2005Drug-resistant strains of HIV will infect 42% of HIV-positive individuals in San Francisco by 2005, according to a mathematical model developed and applied by researchers at the University of California-San Francisco and the University of California-Los Angeles, the San Francisco Chronicle reports. The percentage of people with drug-resistant HIV rose from 0% in 1996, when the protease inhibitors were first introduced, to 28.5% in 1999 and will reach 42% by 2005, according to the model developed by UCLA biomathematician Sally Blower. Blower, who co-wrote the report in the September issue of Nature Medicine, has been using the model to track infectious diseases for nearly 10 years. Preliminary data from San Francisco General Hospital clinics that showed that 28% of patients had drug-resistant HIV in 1999 "suggest" that the model is on target (Russell, San Francisco Chronicle, 8/31). Resistant strains develop when drug therapy does not fully suppress HIV, allowing the virus to learn the drugs' mechanisms and mutate to form drug-resistant strains. Those strains then can be transmitted to other people through unprotected sex or intravenous drug use. According to Blower, however, the "vast majority of new cases come from acquired drug resistance, not sexual transmission" of resistant strains (Beasley, Reuters, 8/31). Blower's model estimated that 8% of new HIV cases in San Francisco last year were drug-resistant, a number consistent with the 9% reported by city clinics (San Francisco Chronicle, 8/31).
Not as Bad as it Sounds
Patients can develop resistance to certain drugs over time or because they did not adhere to often complicated treatment regimes. "The glib answer to the trend is noncompliance on the part of patients, but there are many other factors," Blower said, adding that the way the health care system is structured plays an important role. Some patients get treatment at "state-of-the-art specialty treatment centers" that can help tailor drug regimens and better monitor patients reactions, while others rely on general practioners who are less familiar with the latest treatments (Reuters, 8/31). But drug-resistant strains are weaker than wild-type HIV, and new drugs in development are proving to be effective in suppressing them. "Our work clearly indicates that, as the virus becomes drug resistant, it's capacity to destroy the immune system is also weakened," Dr. Steven Deeks, an AIDS clinician at San Francisco General Hospital, said, adding that although it is "still preferable to have an infection held in check by effective AIDS drugs," the new strains are "by no means a return to the days when the original virus could run amok and wipe out the body's natural defenses."
Developing New Treatment Strategies
Because two new drugs "in the pipeline" show promise in suppressing drug-resistant strains, the problem "ultimately will be controllable," Martin Delaney, founding director of Project Inform, a San Francisco-based advocacy group, said. Blower said that focusing on developing new drugs and getting them to market are the most "important" measures public health officials can take to combat the rise in drug-resistant strains (San Francisco Chronicle, 8/31). She also recommended that doctors postpone antiretroviral therapy "as long as possible" so that patients can get the greatest "medical benefit" from the drugs while "delay[ing] side effects." The creation of more specialty treatment centers that could better monitor a patient's drug response would also cut down on the number of people developing drug-resistant strains, Blower added (Reuters, 8/31).