WASHINGTON — For all the strides made against HIV, the virus that causes AIDS, science and medicine alone can’t end an epidemic that affects vulnerable populations disproportionately: minorities, young people, poor people and those who lack access to health care.

The International AIDS Conference taking place last week in Washington brimmed with hope about breakthroughs in treatment and care that allow people with HIV to live longer and healthier lives. Researchers talk optimistically about a vaccine and a cure.

But because of persistent social, cultural and economic barriers, the most at-risk groups don’t receive enough of the treatment and support necessary to save their own lives and prevent the spread of the virus, health providers and community organizations say.

“The science of HIV and treatment is coming along, and everyone is excited,” said Yvette Calderon, the adult urgent-care director at Jacobi Medical Center in New York. “We forget there’s a real-life implementation that has to occur.”

What 30 years ago was a disease that primarily affected white gay men now has a significant effect on far more populations, including gay and bisexual black and Latino men and heterosexual black women. And while HIV was, and still is, considered a big-city problem, it affects impoverished rural communities at an alarming rate, especially in the Deep South.

According to the Kaiser Family Foundation, blacks are eight times more likely to contract HIV than whites are. Black women are 15 times more likely to become infected than white women. Black youths are 10 times more at risk for HIV than their white counterparts are.

Latinos don’t fare that much better. The nation’s fastest-growing and largest minority population — at 16 percent — is infected with HIV at a rate three times that of whites.

Unlike 30 years ago, HIV no longer means near-certain death. But the groups that are the most likely to be infected with HIV are the least likely to get treatment.