90 percent of new HIV infections in the US come from people not being treated: CDC

More than 90 percent of new HIV infections in the United States could be averted by diagnosing people living with HIV and ensuring they receive prompt, ongoing care and treatment. This finding was published today in JAMA Internal Medicine by researchers at the Centers for Disease Control and Prevention.

Using statistical modeling, the authors developed the first U.S. estimates of the number of HIV transmissions from people engaged at five consecutive stages of care (including those who are unaware of their infection, those who are retained in care and those who have their virus under control through treatment). The research also shows that the further people progress in HIV care, the less likely they are to transmit their virus.

"By quantifying where HIV transmissions occur at each stage of care, we can identify when and for whom prevention and treatment efforts will have the most impact," said Jonathan Mermin, MD, MPH, director of CDC's National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention. "We could prevent the vast majority of new infections tomorrow by improving the health of people living with HIV today."

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The analysis showed that 30 percent of new HIV infections were transmitted from people who did not know that they were infected with the virus, highlighting the importance of getting tested. People who had been diagnosed were less likely to transmit their infection, in part because people who know they have HIV are more likely to take steps to protect their partners from infection.

"Positive or negative, an HIV test opens the door to prevention. For someone who is positive, it can be the gateway to care and the signal to take steps to protect partners from infection. For someone who tests negative, it can be a direct link to important prevention services to help them stay HIV-free," said Eugene McCray, MD, director of CDC's Division of HIV/AIDS Prevention. "At CDC, we're working hard to make testing as simple and accessible as possible."

Today's analysis suggests that simply being in care can help people living with HIV avoid transmission of their virus. According to the model, people who were engaged in ongoing HIV care, but not prescribed antiretroviral treatment, were half as likely (51.8 percent) as those who were diagnosed but not in care to transmit their virus. Being prescribed HIV treatment further lowered the risk that a person would pass the virus to others.

People who were successfully keeping the virus under control through treatment were 94 percent less likely than those who did not know they were infected to transmit their virus. However, previous national estimates have indicated that just 30 percent of people with HIV have reached this critical step in care.

The study authors stress that effective HIV care offers multiple mechanisms to prevent transmission. For example, in addition to antiretroviral therapy, HIV care should include risk reduction counseling on how to protect their partners, screening and treatment for other sexually transmitted infections, and treatment for mental health and substance use disorders.

To estimate HIV transmission at each stage of care in 2009, the new analysis used statistical modeling based on three national HIV data sources: CDC's Medical Monitoring Project, National HIV Surveillance System, and National HIV Behavioral Surveillance System.

This is the latest in a growing body of evidence that prevention of new infections depends on reaching people who are HIV-positive with testing, care, and treatment. CDC has responded by more extensively focusing its prevention strategy on people living with HIV, while continuing to ensure HIV-negative people have tools and information about all available prevention options, including daily pre-exposure prophylaxis .

CDC efforts also include innovative partnerships to make HIV testing simple, accessible, and routine; programs to help health departments and community partners identify and reach out to infected individuals who have fallen out of care; and public awareness campaigns to urge testing and encourage people with HIV to seek ongoing care.