UK scientists on the trail of HIV transmission patterns in heterosexuals
Researchers in the UK have mapped the dynamics of HIV transmission in heterosexuals in the country and revealed a different infection pattern to that of homosexuals. Now published in the open-access journal Public Library of Science (PLoS) Pathogens, the study emphasises that early diagnosis could effectively limit the spread of HIV in this group of individuals. The team of scientists from the University of Edinburgh and the UK's Medical Research Council Clinical Trials Unit investigated the molecular phylodynamics of the HIV strain predominant in heterosexuals in the UK. Phylodynamics analyses the evolutionary relatedness among groups of organisms and makes it possible to reconstruct the pattern of viral sequence divergence in time. Thanks to this method, they were able to uncover transmission patterns. According to the study, out of more than 11,000 patients studied, '296 were linked to at least two others in the UK.' In addition, the research group discovered 8 clusters of more than 10 people that were interlinked, accounting for 5% of the patients involved in the investigation. In homosexuals, 25% of infected individuals show an equivalent interconnection. Transmission in heterosexuals also progressed at a much slower rate than in homosexuals, the study finds, with only 2% occurring within the first 6 months of infection (25% in homosexuals). 'This phylodynamic analysis of non-B subtype HIV sequences representing over 40% of the estimated UK HIV-infected heterosexual population has revealed [that] heterosexual HIV transmission in the UK is clustered, but on average in smaller groups, and is transmitted with slower dynamics than among MSM [men who have sex with men],' the paper reads. 'More effective intervention to restrict the epidemic may therefore be feasible, given effective diagnosis programmes.' 'The slower dynamics of the heterosexual epidemic offer more opportunity for successful intervention, but it is essential that diagnosis [be] achieved as early as possible,' adds University of Edinburgh's Professor Leigh Brown, who led the research group. While in the 1990s genetic characterisation of the virus in heterosexuals showed a predominance of subtype B - the most common form in the Americas, Australia, Europe, Japan, and Thailand - more recent studies find that there has been a shift. Most HIV cases these days in the heterosexual risk group in the UK are of the non-B subtype, 'indicating viruses originating among immigrants from sub-Saharan Africa,' the scientists state. In the past 10 years, the number of HIV infections in heterosexuals in the UK has drastically increased. The UK-based international HIV and AIDS charity AVERT ('Averting HIV and AIDS') talks about a total of 44,617 cases that had been reported by the end of 2008. This exceeds the reported number of infected men who have sex with men. Meanwhile, an HIV vaccine trial in Thailand has shown some promising results, creating quite a buzz in the medical research community and media worldwide. The experimental vaccine - a combination of two earlier experimental vaccines -successfully reduced the risk of HIV infection by nearly one third. The trial was carried out by the US Army and the Thai government, and followed 16,000 participants over 7 years. The World Health Organization (WHO) and the Joint United Nations Programme on HIV/AIDS (UNAIDS) congratulated all parties involved in the Thai study: 'The study results, representing a significant scientific advance, are the first demonstration that a vaccine can prevent HIV infection in a general adult population and are of great importance.' While more work had to be done by the international research community, WHO and UNAIDS said that 'these results have instilled new hope in the HIV vaccine research field and promise that a safe and highly effective HIV vaccine may become available for populations throughout the world who are most in need of such a vaccine'.
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