MANKATO — Robert Gallo remembers the good old days of retrovirus research.

Back in the late 1970s — when the nation was forgetting influenza and polio. When no one had heard of AIDS.

By then Gallo, director of the University of Maryland’s Institute for Human Virology, was already famous for his work on so-called “retroviruses,” superviruses that once contracted can never be eradicated. He’d done groundbreaking retrovirus work on leukemia.

But within a few years, the HIV/AIDS epidemic would present him and other researchers with their greatest challenge yet, a challenge that would transcend medicine and enter realms of politics, cultural differences and ethics.

“We cannot cure it,” Gallo told a crowd gathered Wednesday at Gustavus Adolphus College. “We can only interrupt it.”

Gallo appeared at Gustavus as part of the annual MAYDAY! Peace Conference. He was the morning’s keynote speaker and has been working with students in a two-week residency.

This year’s conference theme was “AIDS and Africa: The Unfolding Crisis.” Other speakers included Marjorie Mbilinyi, a prominent figure in women’s studies in Africa.

Gallo, though, was perhaps the best-known speaker. He and his lab are credited with discovering and isolating the virus that causes AIDS. That breakthrough is credited with saving thousands of lives by allowing blood to be tested before sending it out for transfusions.

His talk was mostly a history lesson in the development of the AIDS crisis, how cultural differences prevented a rapid response in Africa to halt its spread, and how ignorance in the United States set back by five years efforts to develop treatment and educate the public.

Four major factors contributed to the virus’ spread from equatorial Africa to throughout the world.

It was during the early 1980s, Gallo said, that blood began to cross borders for medical purposes. Little to none of that blood had been tested. Travel also boomed during this period, as did sexual promiscuity and intravenous drug use.

Gallo says there have been several great advances that have greatly improved the global AIDS situation: The blood test his lab developed to identify the virus, better AIDS education, and the development of drugs to lengthen the life expectancy of people who contract the virus.

Still, even with those advances, he said, the situation remains grim. There has been a spike in new HIV infections in San Francisco, more people are growing resistant to drugs — including people who have never used the drugs before — and there is still the problem of getting drugs to people in developing nations, and it’s not just Africa.

While Africa may be the worst, India, China, Russia and countries in South America and the Caribbean are experiencing crisis levels of AIDS cases.

Hope, however, may be on the horizon. While Gallo says a cure is still a long way off, a vaccine may not be.

“I see a pathway,” he said. “And I have never seen a pathway before.”

His lab is working with a major pharmaceutical company on developing an HIV vaccine that, if all goes well, could be out within several years.