UNITED NATIONS (Reuters) - Researchers have been undercounting new cases of HIV infection in the United States, meaning the rate is probably 25 percent higher at 50,000 people per year, the nation’s top AIDS doctor said on Tuesday.

File photo shows an AIDS awareness chart displayed at the Aids Center of Queens County needle exchange outreach center in New York November 28, 2006. REUTERS/Shannon Stapleton

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said the rate of infection was not increasing but that new methods of calculating the rate showed infections were more common than previous estimates.

Fauci, attending the United Nations’ 2008 High Level Meeting on AIDS, told reporters the previous methods had shown the rate of new infections in the United States had hit a plateau at around 40,000 per year for the past 14 years.

“They were counting the numbers in a way that was leaving out certain segments of the society. So that 40,000 was probably an undercounted number,” he said.

Instead of using an extrapolated mathematical model to come up with the rate of new infections, he said, the U.S. Centers for Disease Control and Prevention (CDC) was now relying on better counting of more groups, households and regions.

“The number went up to about 50,000. That doesn’t mean that the actual rate of new infections increased. It means that we are now no longer missing counting the ones that we missed early,” Fauci said. “It was always 50,000 a year.”

The new counting methods are not changing the overall picture of AIDS in America, Fauci said.

In the United States, with a population of about 300 million, some 1.1 million people are infected with HIV, of which 25 percent do not know it. That leaves 770,000 documented cases.

“I have seen some of the data and it is clear. The confusion is that it was increasing when in fact it is better accounting,” Fauci said. “They are counting more accurately.”

AIDS activists have accused the CDC of holding back results from the new methods but Fauci believes the statistics will become official “reasonably soon, when the official publication comes out from the CDC.”

Globally, an estimated 33.2 million people are infected with the human immunodeficiency virus that causes AIDS and 25 million have died so far from the fatal and incurable disease.

Fauci said the search for a vaccine was complicated because unlike other viruses that the human body can ultimately defend against, such as polio, measles, mumps or smallpox, “the body does not do a good job making an immune response to HIV.”

On a positive note, drug therapy for treating HIV is proving effective in slowing the disease.

“The good news is that the drugs we have now maintain people with undetectable viruses -- present but undetectable for decades now,” Fauci said.

Fauci noted that the virus disproportionately affects blacks. While blacks make up 12 percent of the U.S. population, 49 percent of new HIV infections in men are among blacks and 65 percent of new infections in women are among blacks.