An international team of scientists has tracked how and when HIV has made its way around Europe. They found that tourists, travellers and migrants actively export the virus from Greece, Portugal, Serbia and Spain to the rest of Europe, and suggest that countries should focus not only on resident populations but also on travellers and visitors when they design and implement programs to tackle the spread of HIV.
The study was the work of first and corresponding author Dr Dimitrios Paraskevis and colleagues and is due to be published soon in the journal Retrovirology. Paraskevis is based at the National Retrovirus Reference Center, Department of Hygiene Epidemiology and Medical Statistics, at the Medical School in the University of Athens, Greece.
He said that:
“Popular tourist destinations like Greece, Portugal and Spain probably spread HIV with tourists infected during their holidays.”
From their results, the researchers found that “in most of the countries in Europe the epidemic was introduced by multiple sources and subsequently spread within local networks”.
However, when they looked at Poland they concluded that HIV spread there mostly because of injected drug users, who make up about half of the HIV-infected population.
HIV-1 subtype B is the most common form of the virus in Europe today. By using samples from 17 different countries in Europe (including Israel), and a technique called “phylogeography”, Paraskevis and colleagues were able to trace the evolutionary family tree of the virus and where it travelled to and from.
They also applied the principle of parsimony, which assumes that the tree most likely to be linked to a migratory event is the one that is formed from the smallest number of evolutionary changes.
Comparing the RNA structures of the possible changes with those prevalent in each area and applying the principle of parsimony they could then see how and when each new virus version went from its starting point to other places in Europe.
In the case of HIV-1 subtype B they found that for three countries, Austria, Poland and Luxembourg, there was hardly any migration outward to the rest of Europe. But from Greece, Portugal, Serbia and Spain, there was a lot of migration of subtype B to other countries.
From Greece the virus spread to seven other countries, and from Spain it spread to five. Other countries also exported the virus, but to a lesser extent. For instance, in the case of Italy there was only one target country: Austria. In the case of Portugal, the virus passed primarily to Luxembourg, whose population is about 13 per cent Portuguese.
The map for Italy, Israel, Norway, the Netherlands, Sweden, Switzerland and the UK showed that the virus went both ways: these countries were both exporters and importers of the virus.
The authors concluded that:
“Subtype B phylogeographies provide a new insight about the geographical distribution of viral lineages, as well as the significant pathways of virus dispersal across Europe, suggesting that intervention strategies should also address tourists, travellers and migrants.”
In their background information the authors describe how HIV-1 Subtype B spread to the United States and elsewhere from a single-point introduction from Haiti in the late 1960s.
It entered Europe mainly as a result of homosexual contacts and needle sharing activity in or from the USA, as well as heterosexual contact with people from Central Africa. Africa is where the virus originated, in chimpanzees.
Although non-B subtypes have been increasing in Europe in recent years, the AIDS epidemic among long term residents is dominated by subtype B viruses.
“Tracing the HIV-1 subtype B mobility in Europe: a phylogeographic approach.”
Dimitrios Paraskevis, Oliver Pybus, Gkikas Magiorkinis, Angelos Hatzakis, Annemarie MJ Wensing, David A van de Vijver, Jan Albert, Guiseppe Angarano, Birgitta Äsjö, Claudia Balotta, Enzo Boeri, Ricardo Camacho, Marie-Laure Chaix, Suzie Coughlan, Dominique Costagliola, Andrea DeLuca, Carlos de Mendoza, Inge Derdelinckx, Zehava Grossman, Osama Hamouda, I M Hoepelman, Andrzej Horban, Klaus Korn, Claudia Kuecherer, Thomas Leitner, Clive Loveday, Eilidh Macrae, I Maljkovic, Laurence Meyer, Claus Nielsen, Eline LM Op de Coul, Vidar Ormaasen, Luc Perrin, Elisabeth Puchhammer-Stöckl, Lidia Ruiz, Mika Salminen, Jean-Claude Schmit, Rob Schuurman, Vincent Soriano, J Stanczak, Maja Stanojevic, Daniel Struck, Kristel Van Laethem, M Violin, Sabine Yerly, Maurizio Zazzi, Charles A Boucher and Anne-Mieke Vandamme.
Retrovirology (in press, expected online during May 2009)
Additional sources: BioMed Central.
Written by: Catharine Paddock, PhD