Using document reviews, semi-structured interviews with key informants, and discussions with officials from specific disease programs, we conducted a task analysis to define the surveillance skills and activities required for implementing surveillance recommendations for each of 19 priority diseases targeted by IDSR. "Skills" were defined as the actions of individual health workers and "activities" as an outcome of the combined skills of one or more health workers. A five-step task analysis enabled reconciliation of several complex surveillance components into a set of skills-based, observable actions [22, 23]. The steps used are outlined below.
Step 1: specify the surveillance and response requirements for each priority disease or condition targeted by IDSR
We reviewed the standard practice guidelines for each specific disease involved in the IDSR strategy to identify the surveillance requirements (for example, standard case definitions, data elements for reporting, thresholds and laboratory testing, and response actions) for each of the 19 priority diseases. We consulted disease experts to confirm and modify our understanding of surveillance and response requirements for each disease. When our search revealed gaps or variations in technical elements, an international technical collaboration team comprised of WHO, CDC and other epidemiologists, disease control experts, laboratory chiefs, and program managers was asked to help standardize the descriptions of surveillance and response activities across disease categories. Their comments were aggregated and common areas of agreement were found. This step resulted in standard surveillance case definitions for both the community and district levels, definitions of surveillance action thresholds for timely public health actions, clarification of the role of laboratory confirmation in suspected outbreaks, and specification of minimum data elements for reporting and analysis.
Step 2: identify the skills and activities that are common to each specific disease and categorize the features within seven core functions – case identification or detection, reporting, analysis, investigation, response, feedback and program evaluation
After we achieved agreement on disease-specific requirements (for example, consistent wording of case definitions), we sorted the recommendations according to surveillance functions. We included laboratory activities within the seven core functions, positioning laboratory support as integral to a public health surveillance system.
Step 3: choose a visual representation of the multi-level, multi-disease system
We selected a matrix format to display the skills and activities selected in step 2 (Figure 3).
Step 4: relate the skills in disease-specific systems with a core surveillance and response function in a multi-level system
Core surveillance and response functions are those activities for detection of cases and patients, registration of cases in log books and registers, confirmation with laboratory results, analysis of reported data, use and feedback of data, and epidemic preparedness and response . Associated support functions that enable implementation of the core surveillance and response activities include coordination, supervision, training, and mobilization of resources .
The column headings listed across the top of the matrix (Identify, Report, Analyze, Interpret, Investigate, Respond, Provide Feedback and Evaluate) incorporate both surveillance and support functions. The levels of the health system – community (typically a village), health facilities, district or intermediate (such as a state or province), national and international (WHO country and regional offices) – were displayed as row headings (see Additional file 1). Each cell in the matrix was a prompt for deciding on the placement of the skills and activities derived in Step 2 . For example, we described dissemination of standard case definitions throughout a national system as a responsibility related to each level in the "Identify" column. This makes explicit the role of the national level to establish standard case definitions and action thresholds. The role of the district or intermediate level is to disseminate the standard case definitions through training, supervision and monitoring. The health facility uses the definitions to identify the cases or outbreaks of the priority diseases or conditions. Simplified case definitions could be used locally to link the community to the health facility and, eventually, to other levels. At all levels it is important to adapt existing systems to local needs.
Step 5: cross-check the assignment of skills and activities to specific functions or levels
To validate the assignment of surveillance skills and activities to specific functions, we conducted multiple review sessions to obtain further feedback and confirmation from disease program and surveillance experts in WHO, CDC, and other public health organizations. One outcome from this step was an observation that the placement of a skill at any one of the levels depended upon the availability of resources and policies that support an individual system. We portrayed this observation with a broken line between rows (representing the levels) to indicate flexibility during adaptation to national contexts and resources. The challenges affecting the placement of the skill at a particular level might be financial (such as when funding limits resources to infrastructure for a single, vertical disease program) but can also be technical (such as lack of skill to inoculate cholera specimens properly into transport media) and cultural (such as reluctance to collect spinal fluid specimens in a meningitis epidemic). This external validation has led to adoption of practical solutions such as more effective resource acquisition, provision of laboratory training kits, and use of culturally sensitive community education.