CDC understated number of new HIV infections in U.S.

ATLANTA — The number of Americans infected by the AIDS virus each year is much higher than the government has been estimating, U.S. health officials reported Sunday, acknowledging that their numbers have understated the level of the epidemic.

The country had roughly 56,300 new HIV infections in 2006 — a dramatic increase from the 40,000 annual estimate used for the last dozen years. The new figure is due to a better blood test and new statistical methods, and not a worsening of the epidemic, officials said.

But it likely will refocus U.S. attention from the effect of AIDS overseas to what the disease is doing to this country, said public health researchers and officials.

“This is the biggest news for public health and HIV/AIDS that we’ve had in a while,” said Julie Scofield, executive director of the National Alliance of State and Territorial AIDS Directors.

The revised estimate by the Centers for Disease Control and Prevention (CDC) and the methodology behind it were presented Sunday, the opening day of the international AIDS conference in Mexico City.

Dr. Lawrence Corey, principal investigator of the nationwide HIV Vaccine Trials Network and co-director of the Vaccine and Infectious Diseases Institute at the Fred Hutchinson Cancer Research Center in Seattle, said in a statement that the ability to report the spread of HIV more precisely is “a great statistical tool, but that is all that it is.”

Corey said the findings should lead to a redoubling of efforts to develop vaccine against AIDS.

“Despite recent setbacks in developing an effective vaccine to prevent HIV infection, I believe that a vaccine is our most promising weapon against new infections,” Corey said. “The research community’s commitment to find a vaccine must not waver.”

Since AIDS first surfaced in 1981, health officials have struggled to estimate how many people are infected each year. It can take a decade or more for an infection to cause symptoms and illness.

One expert likened the new estimate to adding a good speedometer to a car. Scientists had a good general idea of where the epidemic was going; this provides a better understanding of how fast it’s moving right now.

“This puts a key part of the dashboard in place,” said the expert, David Holtgrave of Johns Hopkins University.

Based on the new calculations, officials believe annual HIV infections have been hovering around 55,000 for several years.

“This is the most reliable estimate we’ve had since the beginning of the epidemic,” said Dr. Julie Gerberding, the CDC’s director. She said other countries may adopt the agency’s methodology.

According to current estimates, around 1.1 million Americans are living with the AIDS virus. Officials plan to update that number with the new calculations, but don’t think it will change dramatically, a CDC spokeswoman said.

The new infection estimate is based on a blood test that for the first time can tell how recently an HIV infection occurred.

Past tests could only detect the presence of HIV, so determining which year an infection took place was guesswork — guesswork upon which the old 40,000 estimate was based.