"Both the number and very probably the
concurrency of sexual partners have a
significant impact on HIV transmission
amongst MSM in the UK.
Reducing the number and
concurrency of sexual partnerships
amongst MSM is an appropriate
objective, both ethically and
epidemiologically, for HIV prevention
frameworks in the UK nations. "
http://www.nat.org.uk/media/Files/Publications/July-2010-Parternship-Patterns-and-HIV-Prevention.pdf