20th International AIDS Conference - Melbourne, Australia


THAC0205LB - Oral Abstract Session

A divergent tale of two cities: why has HIV control in men who have sex with men (MSM) differed between London and San Francisco (SF) since 2006?

Presented by Colin Stewart Brown (United Kingdom).

C.S. Brown1,2, M. Das3,4, L. Hsu4, I. Hall5, A. Brown1, A. Aghaizu1, P. Birrell1, N. Carraher4, S. Desai1, J. Hecht6, G. Hughes1, D. Mercey7, A. Nardone1, T. Packer4, F. Post2, A. Zaman1, Z. Yin1, N. Gill1, V. Delpech1

1Public Health England, London, United Kingdom, 2King's College London, London, United Kingdom, 3University of California San Francisco, San Francisco, United States, 4San Francisco Department of Public Health, San Francisco, United States, 5Centers for Disease Control and Prevention, Atlanta, United States, 6San Francisco AIDS Foundation, San Francisco, United States, 7University College London, London, United Kingdom

Background: HIV is endemic in London''s 234,000 MSM (8.7% HIV-positive) and SF''s 64,000 MSM (24.0% HIV-positive). From 2006, in London new HIV diagnoses rose from 563 to 696 per 100,000 MSM, and proportion of prevalent infections undiagnosed remained static at 20-25%. In SF new diagnoses and the proportion undiagnosed fell, from 694 to 442 and from 21.7% to 7.5%, a fall robust to sensitivity analyses. The proportion of new diagnoses shown to be recent is higher in London than SF.
Methods: Extensive HIV surveillance and behavioural data from 2004 in both cities were compared to evaluate how differences in risk behaviour, testing and treatment coverage may account for the possible divergent trends.
Results: HIV testing of HIV-negative MSM increased in both cities but in 2011 was less frequent and annual coverage remained lower in London (16.9%) than SF (34.4%). The proportions of newly-diagnosed MSM linked into care within 3 months (94.5% vs. 82.9%) and total-diagnosed remaining in care (96.0% vs. 76.9%) and virally suppressed (81.7% vs. 65.1%) in 2010 was higher in London (all p=< 0.001). Though fallen in London, reported serodiscordant condomless anal intercourse among MSM was higher in London HIV-negative MSM than SF (17.6% vs. 9.8% in 2008, p=< 0.001). Gonorrhoea rates per 100,000 MSM in 2011 were similar in London HIV-positive and HIV-negative MSM (1910 and 1696 infections, p=0.054), and disproportionately higher in SF HIV-positive MSM (1543 and 487, p=< 0.001).
Conclusions: The apparent reduced proportion of undiagnosed HIV infections and new diagnoses in SF may be associated with the higher proportion of HIV-negative MSM reporting annual HIV testing and safer sex, despite better retention in care and higher viral suppression in London, allowing for those undiagnosed. This emphasises the critical importance for prevention of very high rates of HIV testing, awareness, and disclosure of HIV status. While London may benefit from SF-type intensive interventions, achieving the testing patterns and status disclosure of SF''s smaller, denser, higher prevalence MSM network will be challenging. Furthermore, the safety myth of negative-negative serosorting should be challenged and further study needs to disaggregate HIV-positive/negative MSM risk by viral suppression and use of pre-exposure prophylaxis.

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