People treated for HIV in Switzerland have seen steadily falling rates of resistance to antiretrovirals (ARVs) since 1999, aidsmap reports. Publishing their findings in Clinical Infectious Diseases, researchers analyzed data on 11,084 people in the Swiss HIV Cohort Study who had at least one follow-up between 1999 and 2013.

The researchers divided the data according to three periods: pre-1999, when treatment was suboptimal; 1999 to 2006, when combination treatment improved; and post-2007, when combination treatment boasted high barriers to resistance.

Twenty-nine percent of the overall group had drug resistance, including 56 percent of those who started treatment before 1999, 20 percent of those who started between 1999 and 2006 and 10 percent of those starting after 2007. Only 1.6 percent of those in the most recent treatment group developed resistance while on ARVs. Of the 323 people in the post-2007 treatment group who had resistance, 278 (86 percent) were infected with a drug-resistant strain.

Nine percent of those who started treatment before 1999 had triple-class drug resistance, compared with 4 percent of those who started in 2013.

To read the aidsmap article, click here.