New research indicates potent drug cocktails can disable HIV to the point that the deadly virus can’t be transmitted to other people through sexual activity.

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RALEIGH, N.C. — Groundbreaking research conducted at the University of North Carolina (UNC)-Chapel Hill has demonstrated that potent drug cocktails can disable HIV to the point that the deadly virus can’t be transmitted to other people through sexual activity.

The findings were announced Monday by AIDS researcher Myron Cohen at the eighth International AIDS Society Conference in Vancouver, Canada. Cohen, UNC’s chief of the Institute for Global Health & Infectious Diseases, has headed the global research project for a decade and studied more than 1,700 couples.

The significance of the research findings is that AIDS medications, when used consistently, can break the chain of HIV transmission, with the potential to eradicate the virus when all infected people die natural deaths. For the foreseeable future, however, such a medical strategy will disproportionately benefit industrialized countries whose residents have wider, though far from universal, access to modern health care.

The landmark study, financed with more than $100 million in federal research grants, confirmed initial results reported in 2011 and demonstrated that AIDS medications known as antiretroviral therapy, or ART, can suppress the virus for years. The virus can re-emerge if the patient stops taking the medicine, but as long as it’s suppressed the virus is essentially harmless and most patients can lead normal, healthy lives.

“If people are taking their pills reliably and they’re taking them for some period of time, the probability of transmission in this study is actually zero,” Cohen said from Vancouver. “Let me say it another way: We never saw a case of HIV transmission in a person who is stably suppressed on ART.”

However, researchers are not endorsing a return to the carefree days of unprotected sexual activity.

The study, conducted by the HIV Prevention Trials Network, took precautions to assure that patients were using condoms as an extra safety barrier against sexual transmission of the virus. All study participants received free condoms, risk-reduction counseling, primary medical care and other health services.

Still, Cohen said condoms are not always reliable, or not always used, as documented by the numerous pregnancies recorded during the study.

“This is an important advance along the road to developing a comprehensive prevention plan to the AIDS epidemic,” said Duke University medical professor Barton Haynes, the global health director of Duke’s Human Vaccine Institute and the Center for HIV-AIDS Vaccine Immunology.

“Any preventive measure that is as effective as this treatment, if implemented sufficiently widely, can have a dramatic effect on the epidemic as a whole by breaking the chain of transmission,” Haynes said.

Nationwide, about 1.2 million are infected, a roster that adds 50,000 people annually, according to the Centers for Disease Control and Prevention. Only about 37 percent of the infected are on a regimen of HIV-suppressing antiretrovirals.

“This is the challenge,” Cohen said. “It’s got to be detected, and it’s got to be linked to care.”

The UNC-led HIV prevention study found that the earlier an infected person starts taking antiretrovirals, the quicker the virus is suppressed and sexual transmission blocked.

The study enrolled 1,763 couples in nine countries in Africa, Asia and North and South America between 2005 and 2010. By the end of the study in May of this year, there were 1,171 couples remaining. About 97 percent of the couples were heterosexual.

The research was funded by the National Institute for Allergy and Infectious Diseases, within the U.S. National Institutes of Health. The ART drugs were provided by Abbott Laboratories, Boehringer Ingelheim Pharmaceuticals, Bristol-Myers Squibb, Gilead Sciences, GlaxoSmithKline and Merck.

The study documented eight cases of HIV transmission after the infected patient started taking the ART medications. In four cases, the HIV was transmitted soon after treatment began and researchers concluded the virus jumped to the sex partner before it was fully suppressed by the drug cocktail.

In some cases the virus remained contagious during an interim even after it was no longer detectable in the patient’s blood.

“The soon-after-drugs-are-started is our biggest concern,” Cohen said. “We don’t understand how long people remain contagious.”

In the four other cases, the HIV-infected patient had detectable levels of the virus in the bloodstream. Researchers concluded the patients either weren’t taking the medications as prescribed, or they carried a strain of HIV that developed resistance to one or more drugs in the treatment regimen.