Geopolitical events that affected the movement of people, such as the fall of the Iron Curtain dividing Soviet-controlled Europe and the West, also influenced how the virus spread, according to the new research, published in the Journal of Molecular Epidemiology and Evolutionary Genetics of Infectious Diseases.

"Viral dynamics are influenced by host ecology, and human ecology is defined by geopolitics," co-lead author Gkikas Magiorkinis, of the Department of Zoology at Oxford University in Britain, said.

Europe, particularly western Europe, mostly absorbed the infection from the rest of the world. Photo: European Society for Translational Antiviral Research

The international team of scientists from the European Society for Translational Antiviral Research analysed nearly 9000 genomes of HIV-1 subtype B strains - the dominant HIV subtype in the Americas, Western Europe and Australasia.

They found the spread of the virus mirrored the movement of humans as they crossed continents and oceans for migration, tourism and trade.

Countries and regions with stronger cultural and political links and, therefore, more people travelling between them - for example, western European countries and their former colonies, or North and Central/South America - were the most likely to share viral strains.

The most significant sources of the virus spreading into North America were South America and then Africa. Photo: European Society for Translational Antiviral Research

"A country's influence is strongly linked to its role in spreading the virus - HIV simply followed the natural cultural flows of the second half of the 20th century, moving from North America to Europe," the research said.

North America mostly exported the infection to the rest of the world, while Europe mostly absorbed it, according to the study. Within Europe, the strains of HIV found in the east and west remained clearly segregated until the 1990s - a pattern mirroring the division of Europe during the Cold War era and its reintegration following the collapse of the communist bloc.

"These distinct strains in eastern and western Europe were able to connect again in the 1990s once movement became less curtailed," co-lead author Dimitrios Paraskevis, from the Department of Hygiene, Epidemiology and Medical Statistics at the National and Kapodistrian University of Athens, said.

For Australia, the most significant source of HIV was North America, while the most important sources from Europe were Britain and France, Assistant Professor Paraskevis said.

Australia was also a source country for the spread of HIV to Asia, Europe and Latin America.

"Notably, Oceania is the only continent with bi-directional links with Asia," he said.

Asia was the most isolated region, according to the research.

The findings demonstrate why a global response is needed to combat the spread of infectious diseases like HIV,  according to the authors.

"Much like in economics, an epidemic in an influential country is likely to have an effect in almost every other part of the world," Assistant Professor Paraskevis said.

"This study shows how important it is that policies to prevent the spread of infections are set up on a global scale."