Early warning and NHS Direct: a role in community surveillance?

Background: NHS Direct is a nurse-led telephone help line that covers the whole of England and Wales. NHS Direct derived data are being used for community surveillance, the purpose of which is to detect a local or national increase in symptoms reported by callers. The system has the potential to identify an increase in symptoms reported by callers about people in the prodromal stages of illness caused by the deliberate release of a biological or chemical agent. There are no other community surveillance projects existing on a national scale that utilize electronic daily data.

Methods: We describe the surveillance system and calls to NHS Direct between December 2001 and July 2002. Confidence limits have been constructed for 10 key algorithms at each site and control charts devised for five of these algorithms at sites covering the key urban areas.

Results: Daily reporting has been achieved from NHS Direct sites in England and Wales. High levels of activity in specific algorithms at both national and regional levels have been detected. A sustained national increase in calls about fever occurred in January 2002.

Conclusion: Although the project is still at an early stage, daily analysis of NHS Direct data has the potential to detect symptoms in the community that could be related to deliberate releases of chemical or biological agents or to outbreaks of disease. For this surveillance to act as an 'early warning' of illness resulting from a microbiological or chemical cause, the NHS Direct surveillance needs to be fully integrated into an appropriate public health response (which may require diagnostic samples to be taken from callers).