2007 National HIV Prevention Conference

How the New HIV U.S. Estimates Will Be Decided

By Sharon Egiebor

ATLANTA – The number of people in the United States who are living with HIV is higher than the estimated 40,000 annual new infections, but exactly how high is unclear. The numbers are up for discussion following the CDC’s decision to use new methodology to calculate the extent of the U.S. HIV epidemic.

“The ‘confusion of the numbers’ is the challenge of the disease. A lot of people do not know they are infected,” said Jennifer Kates, HIV policy director for the Kaiser Family Foundation. “It is a disease challenge. We can’t test everybody in the United States or around the world. It is expensive, and it might take 20 years to do. We have to rely on methods that make the best estimates possible.”

Several newspapers, including The Washington Blade and the Washington Post, citing unnamed federal sources and others familiar with the results of the new methodology, say the number is now between 55,000 and 60,000 people.

The Centers for Disease Control and Prevention has reported for more than a decade that the number of new U.S. HIV infections was stable at the estimated 40,000.

This change in U.S. estimates comes on the heels of UNAIDS report that said fewer people than expected worldwide are living with HIV. The United Nation now says there are about 33.2 million people living with HIV and an estimated 2.5 million people were newly infected in 2007. Previously, the U.N. estimated there were 39.5 million, or about 16 percent more people worldwide.

“The single biggest reason for this reduction was the intensive exercise to assess India’s HIV epidemic, which resulted in a major revision of that country’s estimates. Important revisions of estimates elsewhere, particularly in sub-Saharan Africa, also contributed. Of the total difference in the estimates published in 2006 and 2007, 70 percent are due to changes in six countries: Angola, India, Kenya, Mozambique, Nigeria, and Zimbabwe, the report states.

In both Kenya and Zimbabwe, there is increasing evidence that a proportion of the declines is due to a reduction of the number of new infections which is in part due to a reduction in risky behaviours,” the report said.

Dr. Kevin Fenton, the CDC’s director of National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention, said he would not release specific numbers or discuss the data until the methodology and the process of extrapolating the new statistics underwent a “rigorous, independent, scientific peer review.”

“The new estimates utilize complex methods based on a number of statistical assumptions,” Fenton said during a news conference at the 2007 National HIV Prevention Conference in Atlanta. “Any modification to those assumptions during the scientific review process will affect the final estimates. It would not be responsible for CDC to discuss specific data before we are certain that the new estimates are reliable.”

Kates, said there are several reasons the numbers may be are higher than previously estimated. These could include the fact the size of the U.S. population has grown since the estimate was made in the 1990s, the estimated 40,000 was made too late, and HIV numbers are increasing, she said.

“We don’t know how those factors will figure into the estimates,” she said. “At the time the [estimates] were created, we had a very different HIV landscape. The tools that were used then to measure HIV were based on a very different trajectory of the disease. This was the pre-antiretroviral and pre-HAART [Highly Active Antiretroviral Therapy Highly Active Antiretroviral Therapy] days. In the early 1990s, we thought we had a much clearer understanding between HIV infection and the development of AIDS. That has all changed.”

By 1996, HAART therapy changed the disease from an automatic death sentence to being able to live with a chronic disease. A 2005 British study showed an 86 percent drop in the AIDS death when patients took the combination of three-drug cocktails.

Kates said the old HIV numbers were estimated based on the number of AIDS cases identified.

“It wasn’t exact; it was an estimate still. It was done with a range of uncertainty, but that was essentially how it was done,” said Kates. “With the advent of HAART and the changes of case definition of AIDS, that period between HIV and AIDS is less known. We can’t use that same methodology to explain what is happening.”

But since an estimated 25 percent of people living with HIV are unaware of their status, the old calculating method is outdated.

“We’re measuring something that is hard to measure, both scientifically and culturally,” she said.

Under the new available technology, which the Centers for Disease Control and Prevention calls the STAHRS (serological testing algorithm for recent HIV seroconversion) Method, testing focuses on when a person became infected, not just the knowledge that they are HIV positive.

Researcher realized that they could check those HIV positive test results to determine how recently the person was infected. The process is called desensitizing for antibodies. Fewer antibodies would be detected in the HIV positive sample from a person who was recently infected, she said. The more antibodies in a person’s system, the longer they have had the infection.

PEPFAR is using this testing method in pilots and the CDC is working with several states to calculate HIV estimates. However, Kates pointed out, the recent increase in HIV infections in Washington, D.C., were based on the reported number of diagnosed cases, not estimates.

Last year, Washington, D.C. health officials reported 3,269 HIV cases between 2001 and 2006, the highest of any U.S. city. More than 80 percent were among black men, women and adolescents. Among women who tested positive, a rising percentage of local cases, nine of 10 were African American, the Washington Post reported.

Kates said the expected new estimates will most likely show similar trends across the United States.

“I think it is will be a few years before we understand the trends. I think we’ll find richer information about who is likely to be newly infected, and probably that our 40,000 estimates is lower than we expected,” she said.

“Ultimately, the new estimates will be a reminder that there is an HIV epidemic in the United States and that is important for all of us to remember. We know that the people who are disproportionately affected are men who have sex with men of all ethnicities and African Americans. We’ve known that for a while and that is still going to be the case, and that is going to be important in moving forward.”

Sharon Egiebor is the project manager for BlackAIDS.org.