Nearly three quarters of Americans with HIV are raising the risk of death from AIDS and transmission to others because they do not have their infection under control, a US study found on Tuesday.
One in five people with human immunodeficiency virus are unaware that they have the disease, added the report by the Centers for Disease Control and Prevention, released ahead of World AIDS Day on December 1.
Among people who know their HIV status is positive, only about half (51%) get ongoing medical treatment, said the CDC's Vital Signs report.
"Closing the gaps in testing, access to care and treatment will all be essential to slowing the US HIV epidemic," said Jonathan Mermin, director of CDC's Division of HIV/AIDS Prevention.
There are about 1.2 million people living with HIV in the United States, and just 28 percent have what the CDC defines as a viral load that is "suppressed," or less than 200 copies of blood-borne virus per milliliter of blood.
Treatment with antiretroviral drugs has been shown to suppress levels of the virus in 77 percent of people who follow the regimen, and studies have shown it can cut the risk of transmission to a partner by 96 percent.
About 50,000 new cases of HIV arise in the United States each year, and 16,000 people die annually of AIDS.
While the figure of 28 percent suppression is higher than a recent study that found just 19 percent, the CDC cautioned that more needs to be done to make sure people are tested and treated.
"The results in this report indicate that progress has been made; however, continued and intensified efforts are needed," it said.
"Increasing the percentages of HIV-infected persons who remain in HIV care, achieve viral suppression, and receive prevention counseling requires additional effort."