Most new HIV cases are transmitted by people who are undiagnosed or untreated, CDC says

The majority of new HIV infections in the United States -- 80 percent -- are transmitted by people who don't know they have the virus or by people who are diagnosed and not receiving care, according to new data from the Centers for Disease Control and Prevention. 

There are about 39,000 new HIV infections every year, with 50 percent of those cases occurring in the southern states where access to prevention and treatment can be limited. 

It is estimated that over a million people are living with HIV in the United States and that 165,000 don't know they have the virus.  

The CDC recommends that everyone in the country get tested for HIV at least once and that people at increased risk get tested more frequently, said Jonathan Mermin, director of the CDC's National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention. 

"If you take HIV treatment and you suppress the level of virus in your blood that it's undetectable, you have effectively no risk of sexually transmitting HIV," Mermin told CBS News.  

A new federal initiative to end the HIV epidemic in the U.S. aims to reduce new infections by at least 90 percent over 10 years. But the CDC says progress in HIV prevention has stalled in recent years with the rate of new infections leveling off.

"Some of that is because there are still people who don't know they have HIV, there are people who have HIV that aren't accessing the treatment necessary, and some of the people who are eligible for pre-exposure prophylaxis (PrEP), this pill that prevents you from getting HIV, aren't getting it," Mermin said.

Government health officials say ending the epidemic is possible, but it's only going to happen if all these services are available to the people who need them.

"Diagnose, treat, protect, and respond: These are the key strategies in our historic initiative to end the HIV epidemic in America by engaging all the people at risk into comprehensive prevention strategies," CDC Director Robert Redfield said Monday in a news release.