A recent paper by Rekart and colleagues (1) presented the findings of a mass treatment intervention to eliminate an outbreak of syphilis in Vancouver, British Columbia. Following several years of very low reported infectious syphilis rates in British Columbia (less than 0.5 per 100 000 population) (2), with the majority of cases acquired overseas, there was a marked increase in numbers of reported cases from mid-1997 onwards. This was largely due to a geographically localised outbreak in Vancouver's disadvantaged downtown eastside area, with rates reaching 126 per 100 000 in this area in 1999. Sixty five percent of the 277 cases reported were among persons who had contact with a potential source of their infection in or from this area. The outbreak was spread mainly through heterosexual contact, with 42% of patients associated with the sex industry (18% sex workers and 24% clients, (2)). Only 6% of cases were in men who have sex with men (MSM). Given high HIV rates among among injection drug users (IDUs) in Vancouver, and the frequent involvement of female IDUs involved in sex work, rising syphilis incidence could facilitate the spread of HIV infection both within the disadvantaged population of Vancouver's downtown eastside itself, as well as outwards from sex workers through clients into the general population (2).

Traditional public health control measures, which included contact tracing, screening, public education, and condom distribution, had failed to control the outbreak. A targeted mass treatment initiative, involving administration of a single oral dose of azithromycin to people at high risk of infection in the downtown eastside, was implemented in January and February 2000. This strategy was adopted because of the geographical concentration of the at risk population, and the availability of a single dose oral treatment, 1.8g azithromycin. The latter has a long serum half life (68 h), and in recent trials has proved as effective as benzathine benzylpenicillin for treatment of incubating syphilis (3).

Sex workers, their clients, and people reporting recent (unprotected) casual sexual contact, were recruited from the downtown eastside and adjacent municipalities. Treatment doses and information were also given to participants to pass on to otherwise inaccessible peers and sexual contacts, a technique known as secondary carry. The intervention reached 2981 (8.1%) residents aged 15-49 years in the downtown eastside area, and 1055 of the estimated 1300-2600 sex workers in Vancouver. The proportion of clients of sex workers reached is unknown. In order to obtain maximum intervention coverage, no specimens were taken, so it is not known how many of the people who took treatment actually had syphilis.

Following the intervention, there was a significant fall in the mean number of reported syphilis cases from February to July 2000 (monthly mean 6.7 cf 10.2 pre-intervention). Reported syphilis rates returned to pre-intervention rates in September 2000, however, and in 2001 more cases were reported than in 1999.

Results of two previous, smaller, mass treatment interventions in heterosexual groups in North America also showed successful results after 6 months of follow up (4, 5). Such short term decreases in syphilis incidence may not be sustainable, however, and may even have negative consequences on postintervention syphilis incidence rates. Rekart and colleagues caution against the implementation of mass treatment interventions for syphilis, and state that the lack of a sustained effect of the intervention is likely to be due to a failure to reach and treat high enough proportions of the marginalised and inaccessible sections of the target population (1). Targeted mass treatment may have increased the pool of susceptible, high risk individuals who were subsequently exposed to infectious syphilis by those people who were not reached by the intervention.

A number of countries in western Europe have recently experienced localised outbreaks of syphilis (6, 7, and references therein). Mass treatment would not, however, be an appropriate and effective intervention in this context, because the majority of outbreaks have predominantly involved MSM who have attended social venues such as saunas and clubs, and who are not geographically and demographically localised in the same way as the Vancouver outbreak.

Nevertheless, the Vancouver study is a good example of the use of community and peer outreach as a means of accessing marginalized, 'hard to reach' groups at high risk of HIV/STI infection. The syphilis outbreaks in both Vancouver and Europe challenge traditional public health approaches to STI control, particularly in terms of contact tracing and treatment. In Vancouver, 46% of index syphilis cases were unable or unwilling to name their sexual contacts (2); similarly, in the United Kingdom, high proportions of MSM who have syphilis are unable to name their sexual contacts. Innovative approaches such as targeted peer outreach combined with non-invasive sampling techniques such as saliva collection, could aid case detection and prompt treatment of infected individuals. Social network methods (8) could also be useful to augment traditional sexual contact tracing procedures. In addition, syphilis screening should be offered to all pregnant women as a matter of course in Europe, in order to prevent congenital transmission (9).

Finally, it should be noted that the conclusions drawn from the Vancouver intervention are not necessarily applicable to developing countries, particularly in sub-Saharan Africa, where extremely high HIV and STI incidence rates in the core group of sex workers, coupled with lack of access to appropriate healthcare and STI diagnostic facilities, may in some contexts justify administration of rounds of mass treatment for STIs at very regular intervals. Such an approach was implemented in a South African mining community, where a directly observed 1g dose of azithromycin was given every month to sex workers attending a mobile clinic. This resulted in significant declines in the prevalence of Chlamydia trachomatis, Neisseria gonorrhoeae, and clinically observed genital ulcer disease in sex workers. Decreased rates of symptomatic STIs were also observed in the client group of miners in the intervention area (10).

European Conference on Syphilis Outbreaks & Management - London, 17 March 2003

Twenty places are available for the above meeting to be held at the Communicable Disease Surveillance Centre (Colindale, London, UK). If you would like to attend please contact Maria Solomou (tel: 020 8200 6868 ext 4574 email: msolomou@phls.org.uk). There is no conference fee but attendees will have to meet their own travel expenses.