WASHINGTON A new estimate of how many Americans have the AIDS virus puts the number at about 1.1 million, the U.S. Centers for Disease Control and Prevention said on Thursday.
The CDC numbers, based on 2006 data, show the population living with HIV is growing as people become newly infected and as more patients survive thanks to HIV drugs.
The report also suggests that past estimates that more than 1 million Americans were living with HIV overstated the actual total number of people with HIV infections at the time.
The agency used different methods than it has in the past to calculate the number. Its most recent nationwide estimate of 1 million had been given for 2003, and using the new methods the CDC figured that 994,000 were living with HIV that year.
"These data really show the continued impact that the epidemic is having on Americans, and they really reinforce the severe toll that is experienced in multiple communities," the CDC's Richard Wolitski said in a telephone interview.
The CDC report reinforced previous findings that the epidemic disproportionately affects blacks of both sexes as well as gay and bisexual men.
As the number of people living with HIV grows, so does the cost of providing medical services to this population and the burden on the U.S. health care system, Wolitski said.
The CDC estimated that about one in five -- 232,700 of the 1.1 million people infected with the human immunodeficiency virus that causes AIDS -- did not know they were infected. The total U.S. population is 300 million.
"We're not going to be able to treat our way out of this epidemic. We need to have strong prevention programs so we can prevent these infections from occurring in the first place," said Wolitski, acting chief of the CDC's HIV/AIDS prevention division.
Men made up three quarters of people with HIV infections.
The CDC previously reported that more people are becoming infected each year than previously estimated, with 56,300 new HIV infections in the United States in 2006. Previous estimates put the number of new infections at about 40,000 a year.
Of all the people infected with HIV, 48 percent were men who have sex with men, the CDC said. While male-to-male sexual contact was the leading cause of HIV infections, heterosexual sex -- mostly women having sex with men who are injection drug users -- accounted for 28 percent of HIV-infected people.
Injection drug use, which spreads the blood-borne virus via contaminated needles, contributed 19 percent of the HIV cases.
Blacks make up 12 percent of the overall population but accounted for 46 percent of those infected with HIV (510,100 people). About 35 percent of those with HIV were white and 18 percent were Hispanic, according to the CDC.
Black women were nearly 18 times more likely than white women to be infected with HIV, while black men were six times more likely than white men, the CDC said. Hispanics were 2.6 times more likely than whites to be infected.
In 2006, about 14,000 Americans died of AIDS. At the end of 2006, the disease had killed nearly 546,000 Americans since being first recognized in the early 1980s.
To make the new estimates, the CDC used information on new HIV diagnoses taken from 40 states with the best data and AIDS diagnoses and deaths taken from all 50 states, as well as a statistical method called "back-calculation."
Globally, 33 million people have HIV and 25 million have died of it.