The rate of new HIV infections in the United States has plateaued at about 50,000 a year for the last decade, but young gay and bisexual men, particularly African-Americans, have suffered an increase.

The 50,000 new cases a year number, reported by the U.S. Centers for Disease Control and Prevention, represents a sharp decline from the epidemic's peak of about 130,000 new cases in the 1980's. But infection rates were rising among young gay and bisexual men, with a spike of 48 percent among those were African-Americans.

"We're very concerned about these increases among young gay men," Dr. Kevin Fenton, director of the CDC's National Center for HIV/AIDS, told Reuters. "We can't allow the health to a new generation to be lost to what is essentially a completely preventable disease.

Fenton said the data points to significant progress in cutting the rate of new infections by more than half since its peak. But he said that 50,000 remains an "unacceptable level" and said that without the government bolstering its prevention efforts, "we're likely to face an era of rising infection rates." Meanwhile, activists said that the stalled rate of new infections suggests the government is faltering in its efforts to tame the epidemic.

"It means I don't see an AIDS policy, and I don't see anyone in charge," longtime activist Larry Kramer told the New York Times. "It's so dispiriting that it's hard to find something to say about it."

Scientists believe they have reached a watershed moment in combating HIV/AIDS, as the emphasis shifts to early preventative treatment. A widely hailed study found that having people begin taking medication early and often can diminish their chance of transmitting the disease by as much as 96 percent. People said the CDC data signaled the need to redouble efforts at expanding access to preventative treatment.

"We've failed to target prevention services adequately and have not gotten treatment coverage in many communities that would bring down community viral loads," said Chris Collins, director of public policy for the Foundation for AIDS Research.

The number of infections through drug use dropped by 80 percent, which may reflect the declining prevalence of needle drugs like heroin.