Strengthening public health systems: assessing the attributes of the NSW influenza surveillance system

In New South Wales (NSW), influenza surveillance is informed by a number of discrete data sources, including laboratories, emergency departments, death registrations and community surveillance programs. The purpose of this study was to evaluate the NSW influenza surveillance system using the US Centers for Disease Control and Prevention guidelines for evaluating public health surveillance systems. Importance of study: Having a strong influenza surveillance system is important for both seasonal and pandemic influenza preparedness. The findings will inform recommendations for strengthening surveillance in NSW.

The scope was limited to all sources included in the NSW Health Influenza Report in 2012-13. To assess the performance of the system, in-depth interviews (N = 21) were conducted with key stakeholders and thematically analysed. Respiratory testing data gathered through the sentinel laboratories in 2012 were used to estimate sensitivity, and laboratory notifications were analysed to assess timeliness and representativeness. Key documents - including reports, guidelines, correspondence and meeting minutes - were also reviewed, providing a method of triangulation.

The NSW influenza surveillance system integrates multiple sources of surveillance of influenza and influenza-like illness to provide a comprehensive picture of influenza in the community. Despite its structural complexity, the system delivers quality, timely and relevant data to inform a range of public health activities, and the NSW Health Influenza Report is well regarded by stakeholders. Challenges include managing system complexity, key person risk and cross-jurisdictional issues. Stakeholders commented that system flexibility would depend on additional resourcing. Although the sensitivity of sentinel laboratory surveillance was estimated as 1-25%, depending on the time of year, understanding sensitivity remains a challenge in influenza surveillance where the true incidence of infection is unknown.

Influenza surveillance is critical for monitoring virological changes, understanding disease epidemiology and informing public health responses. The system was found to deliver timely and good-quality surveillance information. Additional value could be achieved by increasing flexibility and stability, automating systems (where possible) and formalising processes of data acquisition. The system continues to negotiate a number of constraints, including complexity and cross-jurisdictional issues, which are ongoing obstacles to realising some potential system improvements.