WASHINGTON, Nov. 25 -- Only 30 percent of Americans living with HIV have the virus under control, according to a report released Tuesday by the U.S. Centers for Disease Control and Prevention (CDC).

The report also estimated that approximately two-thirds of those whose virus was out of control in the United States had been diagnosed but were not receiving regular care.

According to the CDC, antiretroviral medication can keep HIV controlled at very low levels in the body when used consistently, allowing people with HIV to live longer, healthier lives and reducing the likelihood they will transmit HIV to others.

Treatment has been shown to reduce sexual transmission of HIV by 96 percent, and U.S. clinical guidelines now recommend that everyone diagnosed with HIV receive treatment, regardless of their viral load.

"For people living with HIV and AIDS, it's not enough to know, you also have to go to health care," CDC Director Tom Frieden told a telebriefing.

"For health care systems ... it's not enough to diagnose patients, you have to take accountability and responsibility for every patient diagnosed in your health center ... to provide them with the most sensitive, effective, culturally appropriate care so that they will get onto treatment, stay into treatment, live longer, live healthier, stay out of the hospital, and not infect others."

According to the CDC, more than 1 million Americans are living with HIV and there are an estimated 50,000 new infections each year.

In 2011, among the nearly 840,000 people who didn't have their virus in check, 20 percent did not yet know they were infected, 10 percent were prescribed antiretroviral treatment but did not get the virus under control, and 4 percent were engaged in care but not prescribed antiretroviral treatment.

The study also found that young people were significantly less likely than older age groups to have their virus under control. Only 13 percent of people aged 18-24 were virally suppressed, compared to 23 percent among those aged 25-34, 27 percent among those aged 35-44, 34 percent among those aged 45-54, 36 percent among those aged 55-64, and 37 percent among those aged 65 and older.

The researchers attribute the disparity in large part to the fact that fewer than half of 18-to-24-year olds with HIV have been diagnosed.

"It's alarming that fewer than half of HIV-positive young adults know they are infected," said Eugene McCray, director of CDC's Division of HIV/AIDS Prevention. "Closing that gap could have a huge impact on controlling HIV."