Half of all black gay and bisexual men in the United States are projected to be diagnosed with HIV, a government study shows, in a ratio parallel to the prevalence of the virus among such men in developing nations such as Mauritania and Senegal.

Black men who have sex with men are 250 times more likely as heterosexual American men overall to be diagnosed with the virus, according to the report by the Centers for Disease Control and Prevention (CDC).

Among Latino gay and bisexual men, one in four are projected to get HIV in their lifetime, and the chance of white gay and bisexual men getting HIV is one in 11, said the report released this week.

The figures are a reminder that efforts need to be made to boost HIV and AIDS prevention, CDC officials said.

“Hundreds of thousands of people will be diagnosed in their lifetime if we don’t scale up efforts now,” said Jonathan Mermin, director of the CDC’s National Center for HIV/AIDS, Viral Hepatitis, STD, and Tuberculosis Prevention.

The projections for gay black men in the United States evoke the rates of HIV and AIDS in African nations such as Mauritania, where some 44 percent of gay and bisexual men had HIV in 2014, according to the United Nations program on HIV/AIDS (UNAIDS).

The same year in Senegal, nearly 42 percent of gay and bisexual men had the virus, UNAIDS said.

In the United States, more than 1.2 million people have HIV, according to CDC data. Worldwide, some 36.9 million people were living with HIV at the end of 2014, according to UNAIDS.

Globally, HIV infections have been falling since AIDS-related deaths peaked in 2004.