Health officials estimate 1 in 99 Americans will be diagnosed with the AIDS virus in their lifetime. They also say the risk is declining.

But for gay black men, as many as 1 in 2 will get HIV.

HIV is spread mainly through sex and sharing needles for injecting drugs. Infections are most common in men who have sex with men.

The Centers for Disease Control and Prevention released the estimates Tuesday at a medical conference in Boston. Previously, the health agency had put the odds at 1 in 78 for all Americans.

It found wide differences in lifetime risk based on race, sexual orientation and location.