The United States has significantly underreported the number of new H.I.V. infections occurring nationally each year, with a study released here on Saturday showing that the annual infection rate is 40 percent higher than previously estimated.
The study, conducted by the Centers for Disease Control and Prevention, found that 56,300 people became newly infected with H.I.V in 2006, compared with the 40,000 figure the agency has cited as the recent annual incidence of the disease.
The findings confirm that H.I.V., the virus that causes AIDS, has its greatest effect among gay and bisexual men of all races (53 percent of all new infections) and among African-American men and women.
The new figures are likely to strongly influence a number of decisions about efforts to control the epidemic, said the disease centers’ director, Dr. Julie L. Gerberding, and other AIDS experts. Timely data about trends in H.I.V. transmission, they said, is essential for planning and evaluating prevention efforts and the money spent on them.
“C.D.C.’s new incidence estimates reveal that the H.I.V. epidemic is and has been worse than previously known,” Dr. Kevin A. Fenton, who directs H.I.V. prevention efforts at the agency, said on Saturday.
A separate historical trend analysis published as part of the study suggests that the number of new infections was probably never as low as the earlier estimate of 40,000 and that it has been roughly stable overall since the late 1990s.
