The importance of treating people with HIV with antiretroviral drugs is greater than ever, British Columbia researchers say, after they discovered a significant drop in new HIV diagnoses when more people were treated with the drug cocktails.
The notion that treating HIV can reduce the chances of the disease spreading - and therefore is also an effective means of prevention - "is a true game changer," Dr. Julio Montaner, lead researcher of the study and director of the B.C. Centre for Excellence in HIV-AIDS, said at the International AIDS Society conference in Vienna on Sunday.
The research is one of several studies that have encouraged the United Nations Program on HIV-AIDS to change its approach to the epidemic and view treatment as a prevention tool.
Researchers observed a 3-per-cent decrease in HIV diagnoses in B.C. for every 100 patients who used the treatment, called highly active antiretroviral therapy.
As use of HAART in B.C. increased 547 per cent between 1996 and 2009, the number of new HIV diagnoses fell 52 per cent, according to the study.
Antiretroviral drugs, which can slow the progression of HIV-AIDS symptoms, decrease viral loads in plasma and other biological fluids, the study said.
The findings dramatically enhance the return on investment for the therapy, and bolster the campaign for treating people earlier and more broadly because they will be less likely to infect others, Dr. Montaner said.
The researchers conducted a population-based study using data from B.C., where HIV care is free. The study also found a decrease in new HIV diagnoses in a more concentrated population base of intravenous drug users.
"Our work in Vancouver has shown the dramatic value of HAART in decreasing HIV incidence among injection drug users," Dr. Montaner said.
Sexually transmitted infection rates increased during the period of time researchers studied, which suggests the drop in diagnoses wasn't because people took part in less risky sexual behaviour, the study said.
Researchers considered whether the drop in new HIV diagnoses could have also been a result of reduced testing, but found the total number of tests done in the province actually increased during the study.
While the study shows a correlation between use of HAART and HIV diagnoses, researchers said the results are not conclusive proof of causality.
Researchers gathered information about patient viral loads, cell counts and drug-cocktail use from the B.C. AIDS centre, and figures for the number of HIV tests done and new HIV diagnoses from the B.C. Centre for Disease Control.
More than 33 million people in the world are living with HIV, according to UNAIDS. There is no cure and no vaccine for the virus.
The study was published Sunday in the medical journal The Lancet.