Surveillance of sexualised drug use - the challenges and the opportunities.

Sexualised drug use (SDU), the use of drugs in a sexual context, has emerged as a marker of high-risk sexual activity and poor sexual health among gay, bisexual and other men who have sex with men, however, there are no robust estimates of the prevalence of SDU. The primary sources of surveillance data on SDU should include both sexual health and drug treatment services. The challenges to achieving comprehensive, timely and valid SDU surveillance include establishing case definitions, selecting appropriate surveillance settings, and normalising the monitoring of SDU at clinical services. In this commentary we propose a means to address these challenges and discuss other sources of SDU data from ad hoc population surveys and sentinel systems. We also present case studies of SDU surveillance development in England and Switzerland. The patterns of SDU will be affected by a rapidly changing drug market and, as a result, surveillance systems must continuously adapt to ensure that they are fit for purpose and can provide data to guide policy.