In 2011, as part of the World Health Organization global reporting tool to collect data on the progress of improving the health sector response to HIV/AIDS towards universal access, a questionnaire was sent to ministries of health of Western Pacific Region Member States on the scope and functioning of their HIV surveillance systems. Of the 17 countries that responded, 13 were low- to middle-income countries and four were high-income countries. Regular serosurveillance surveys are conducted with female sex workers in all lower- and middle-income countries that responded to the survey but less so with people who inject drugs and men who have sex with men. Furthermore, there are no surveillance activities of the key populations in most of the Pacific island countries. It is recommended that estimations of high-risk populations be conducted in priority Pacific island countries and tailored surveillance systems be designed. Efforts should also be made to gather and accumulate data from sufficient geographic coverage to allow the HIV epidemic to continue to be monitored.

Problem:Size estimates of key populations at higher risk of HIV exposure are recognized as critical for understanding the trajectory of the HIV epidemic and planning and monitoring an effective response, especially for countries with concentrated and low epidemics such as those in Asia. Context:To help countries estimate population sizes of key populations, global guidelines were updated in 2011 to reflect new technical developments and recent field experiences in applying these methods. Action:In September 2013, a meeting of programme managers and experts experienced with population size estimates (PSE) for key populations was held for 13 Asian countries. This article summarizes the key results presented, shares practical lessons learnt and reviews the methodological approaches from implementing PSE in 13 countries. Lessons learnt:It is important to build capacity to collect, analyse and use PSE data; establish a technical review group; and implement a transparent, well documented process. Countries should adapt global PSE guidelines and maintain operational definitions that are more relevant and useable for country programmes. Development of methods for non-venue-based key populations requires more investment and collaborative efforts between countries and among partners.