British Columbia offers solid, real-world evidence that the HIV treatment as prevention (TasP) strategy is highly effective, as wider use of antiretrovirals (ARVs) in the Canadian province has been linked to a marked drop in new infections. Publishing their findings in PLOS ONE, researchers drew HIV-related health and medication data from registries across the province covering 1996 through 2012.

As the use of ARVs expanded dramatically throughout this time period, CD4 levels upon starting therapy rose and medication adherence rates increased. These three variables were linked to improved viral suppression rates as well as a drop in drug resistance rates.

The rate of annual new AIDS diagnoses fell 80 percent, from 6.9 to 1.4 per 100,000 people. The rate of HIV-related deaths also fell 80 percent, from 6.5 to 1.3 per 100,000 people. New HIV diagnoses dropped by 66 percent, from 702 cases in 1996 to 238 in 2012. There was a 42 percent drop in estimated new HIV infections, from 632 to 368.

According to the researchers' mathematical models, each increase of 100 people taking ARVs led to a decrease of annual new HIV cases of 1.2 percent. Also, for each 1 percent rise in the number of people with a fully suppressed viral load as a result of ARV treatment, new HIV cases dropped by 1 percent.

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