The price of success

日期:2019-03-08 07:17:01 作者:梅牖梃 阅读:

By Jonathan Knight THE number of new cases of HIV could increase even if most sufferers were taking the best treatment now available. A mathematical model of San Francisco’s gay population shows that the widespread use of potent drug combinations could lead to the spread of drug-resistant strains if patients do not take the right doses at the right times. Currently, 30 per cent of gay men in San Francisco are infected with HIV. Of those, roughly a third receive the most effective drug combination now available, known as highly active antiretroviral therapy (HAART). Sally Blower, an epidemiologist at the University of California, San Francisco, expects the number of patients on HAART to grow rapidly. She and her colleagues have been trying to work out how many new cases of HIV they would expect over the next 10 years if up to 90 per cent of infected men took the drug combination. From her knowledge of HIV, Blower derived equations that include terms for how often the virus is transmitted and how easily it becomes resistant to drugs. If the virus becomes drug resistant only as often as it has done in clinical trials of HAART, there will be 20 per cent fewer new cases of HIV in San Francisco 10 years from now, the model predicts. Furthermore, if risky sexual activity among gay men—which has risen recently—were to fall by half, there would be only half as many new cases. But Blower says it is likely that drug resistance will emerge more often when more people are using HAART. Outside the tightly controlled environment of a clinical trial, patients are more likely to take drugs at the wrong time or miss doses completely, increasing opportunities for resistant strains to arise. Doctors may also prescribe the wrong doses. “The more people [who use HAART], the worse it gets,” says Blower. In this case, her model predicts that the number of new HIV infections in San Francisco will rise by 15 per cent if 90 per cent of HIV-positive gay men are taking HAART. “It could be a disaster,” says Blower. One way to avoid the problem would be to extend the strict regime of monitoring patients used in clinical trials to all HIV-positive patients. Drugs companies are also trying to simplify HAART, which involves taking many different pills at different times. If fewer pills were needed,