Syndromic surveillance of influenza-like illness in Scotland during the influenza A H1N1v pandemic and beyond

Syndromic surveillance refers to the rapid monitoring of syndromic data to highlight and follow outbreaks of infectious diseases, increasing situational awareness. Such systems are based upon statistical models to described routinely collected health data. We describe a working exception reporting system (ERS) currently used in Scotland to monitor calls received to the NHS telephone helpline, NHS24. We demonstrate the utility of the system to describe the time series data from NHS24 both at an aggregated Scotland level and at the individual health board level for two case studies, firstly during the initial phase of the 2009 Influenza A H1N1v and secondly for the emergence of seasonal influenza in each winter season from 2006/07 and 2010/11. In particular, we focus on a localised cluster of infection in the Highland health board and the ability of the system to highlight this outbreak. Caveats of the system, including the effect of media reporting of the pandemic on the results and the associated statistical issues, will be discussed. We discuss the adaptability and timeliness of the system and how this continues to form part of a suite of surveillance used to give early warnings to public health decision makers.