Provocative new research shows that treating people with the AIDS virus can provide a powerful bonus: It cuts the risk that they will infect others.
New infections plummeted in parts of Canada as more people went on AIDS drugs, which lowered the amount of virus they had and the chances they would spread it, the study found.
For every 100 people with HIV who started taking AIDS drugs, new infections dropped by 3 percent in British Columbia, where the study was done. The number of new infections there has been cut in half since 1996, matching a rise in treatment.
“The more people you put on therapy, the less transmission there is,” said Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases. The drop in new cases in Canada “likely could not be explained by anything else,” he said.
The U.S. government helped pay for the study. Results were published online July 18 by the British medical journal Lancet and were being presented at the International AIDS Conference in Vienna.
The results suggest that Canada's policy of free AIDS care is having a double benefit: to the people being treated and to the public's health.
In the United States, the study should boost efforts to more aggressively test and treat people, and to plug funding gaps that keep many from getting care now, AIDS experts said. An estimated 1.1 million Americans have HIV, and about 20 percent of them don't know it. About 55,000 new infections occur each year in the U.S., a number that has held steady for a decade.
Finding ways to prevent HIV infection is critical because there is no vaccine or cure for AIDS. Recommended treatment is a combination of medicines that lower the amount of virus that infected people harbor, often to undetectable levels.
A study a decade ago in Africa found that people with these very low levels of virus were less likely to infect others. Treating pregnant women with HIV lowers the amount of virus they have and the risk they'll pass it on to their babies.
The new study is the first clear evidence that the same principle holds true on a population level, in everyday community settings.
It was led by Dr. Julio Montaner, director of the British Columbia Centre for Excellence in HIV/AIDS in Vancouver.
Researchers used patient registries from British Columbia's universal health care system to track HIV tests, new cases, treatments and virus levels since 1996, when modern AIDS drugs became available.
The number of infected people getting treatment rose from 837 in 1996 to 5,413 in 2009. The number of new HIV diagnoses fell from 702 to 338 per year during that time. The amount of virus that patients harbored also dropped and was directly related to fewer new cases being diagnosed in the population.
The trends were largely driven by more treatment and fewer new cases among injection drug users, as sharing needles raises the risk of spreading HIV.
Rates of other sexually spread diseases rose during the study period, suggesting that safer sex behaviors were not responsible for the drop in new HIV infections – treatment was.
“There's an ethical imperative'' to provide care to people with HIV, and finding that this helps prevention “is an added bonus,'' said Dr. Jonathan Mermin, the federal Centers for Disease Control and Prevention's AIDS prevention chief.
“It's not enough on its own to stop the epidemic'' and must be combined with safe sex and other prevention strategies, he said.
Mitchell Warren, executive director of the AIDS Vaccine Advocacy Coalition, a New York-based nonprofit group that has worked toward developing a vaccine and other prevention tools, said the study was “quite compelling” and “very strong evidence” that treatment cuts the risk of spreading infection.
Nearly every country, including the U.S., has waiting lines for people to get treatment, he noted. And progress with this approach depends on getting more people tested.
Aggressive efforts to test and quickly treat anyone found to have HIV are under way in Washington, New York and San Francisco. The National Institutes of Health also has a study under way in seven countries, including the United States, to see if HIV treatment helps prevent spread of the virus to an uninfected partner.
AP Medical Writer Mike Stobbe in Atlanta contributed to this report.
Photo. HIV Virus budding on a cell.
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AIDS conference: www.aids2010.org and www.kff.org/aids2010