A recent study published Tuesday in the Proceedings of the National Academy of Sciences tracks the acquired immune deficiency syndrome (AIDS) from its African origins to the present.

There have been 25 million deaths because of AIDS and more than 40 million people have become infected with HIV to this day.

Researchers have studied several of the first blood samples kept frozen by the national Centers for Disease Control and Prevention. They were collected in 1982 and 1983 from Haitian AIDS patients in Miami.

Previously, it had been believed that AIDS was introduced in the United States in the early 1980s by a Canadian flight attendant.

This research shows that today’s most widespread subtype B first emerged in Haiti in the 1960s and had been brought to the United States several years later, by Haitian immigrants.

The study discovers the AIDS path from 1930, when it first appeared in humans in Africa, probably when people slaughtered infected chimpanzees for meat, until 1981 when it was first considered as a disease by scientists.

Michael Worobey, an evolutionary biologist at the University of Arizona and senior author of the study, and his colleagues compared Haitian HIV infected blood samples and virus samples from Central Africa with viruses from around the world.

Because viruses constantly mutate, they were able to construct a rough timeline of virus development comparing how much the viruses today have drifted away from their first African form. This way, they could establish with a 99.7 percent certainty that today’s most US common HIV subtype B originated in Haiti.

Worobey believes that today’s HIV virus was brought firstly to Haiti by Haitian workers who had gone to the Democratic Republic of Congo, formerly known as Zaire, and then it was carried to the United States by Haitian immigrants between 1966 and 1972.

The disease multiplied within a couple of years, infecting almost a hundred people, “and then, as with epidemic expansion, at some point the hundred becomes 200, you start getting into thousands, tens of thousands. And then quite rapidly you can be up into the hundreds of thousands of infections that were probably already there before AIDS was recognized in the early 1980s,” Worobey said.