Among heterosexuals in the United Kingdom (UK), HIV transmission can occur
within networks of as many as 30 people, according to a new study by
researchers at the University of Edinburgh, Scotland, and the Medical
Research Council Clinical Trials Unit, London. Details are published
September
25 in the open-access journal PLoS Pathogens.

The number of HIV-infected heterosexuals in the UK has been growing
dramatically and now exceeds the number of HIV-infected homosexual men.
Most are
immigrants from sub-Saharan Africa, a group for which the pattern of virus
transmission is poorly documented.

To better understand the dynamics of the heterosexual HIV epidemic within
the UK, the research group, led by Professor Andrew Leigh Brown, applied
the
novel technique of phylodynamics, which reconstructs the pattern of viral
sequence divergence in time in order to reveal the size of transmission
clusters and the dynamics of transmission within them.

The team studied virus gene sequences from over 11,000 infected
individuals, comprising 40% of the HIV-infected heterosexual population in
the UK,
making this one of the largest studies of its kind to date. By analyzing
differences between the viral strains, they found clusters of related
viruses
that showed 5% of HIV transmissions to have occurred in networks of more
than 10 people

The authors note the importance to their work of the UK HIV Drug
Resistance Database, which contains viral DNA sequence information from
over 30,000
infected individuals. Using this database, the researchers discovered that
transmission clusters in the heterosexual population were smaller than
those found among HIV-infected homosexual men and that transmission was
also much slower. The study concludes that heterosexual transmission could
be
significantly reduced by early diagnosis and treatment.

“The slower dynamics of the heterosexual epidemic thus offer more
opportunity for successful intervention, but it is essential that
diagnosis is
achieved as early as possible,” said Professor Leigh Brown.

Financial Disclosure: This work was supported by the Medical Research
Council. The UK HIV Drug Resistance Database is partly funded by the
Department
of Health; the views expressed in the publication are those of the authors
and not necessarily those of the Department of Health. Additional support
was provided by Boehringer Ingelheim, Bristol-Myers Squibb, Gilead,
Tibotec (a division of Janssen-Cilag Ltd) and Roche. The funders had no
role in
study design, data collection and analysis, decision to publish, or
preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests
exist.

Citation:
“Molecular Phylodynamics of the Heterosexual HIV Epidemic in the United Kingdom.”
Hughes GJ, Fearnhill E, Dunn D, Lycett SJ, Rambaut A, et al. (2009)
PLoS Pathog 5(9): e1000590. doi:10.1371/journal.ppat.1000590

Source
PLoS Pathogens