National Aids Trust.
"Available evidence indicates
many MSM in the UK have high
numbers of sexual partners
and that there are significant
opportunities for sexual mixing.
Given the importance of partnership
patterns to HIV transmission, we should
look at what we know about such patterns
amongst MSM in the UK. The 2007
Gay Men's Sex Survey states:
'As every year, respondents were
very varied in their number of sexual
partners. Among the men who had a
male sex partner in the last year, 21.4%
indicated they had one male partner
only; 27.6% had two, three or four
male partners; 24.4% had between five
and twelve male partners; 13.4% had
between thirteen and 29 male partners;
and the remaining 13.4% had thirty or
more male partners in the last year'"

"In short, evidence suggests a strong
association between higher partner
numbers and infection with HIV as well
as other STIs"

http://www.nat.org.uk/media/Files/Publications/July-2010-Parternship-Patterns-and-HIV-Prevention.pdf