Can calls to NHS Direct be used for syndromic surveillance?

This study assessed whether NHS Direct could be a useful source of surveillance data for communicable diseases, using influenza as a pilot condition. Data on the weekly total number of calls and the number from people reporting influenza-like symptoms to three pilot NHS Direct sites were collected between November 1999 and March 2000. NHS Direct data were compared with routinely available influenza surveillance data. The NHS Direct call rate peaked at 331 per 100,000 population in week 52 of 1999. The percentage of calls for 'influenza-like illness' (one site) peaked at 15% during week 51. Information about weekly call numbers to NHS Direct could be produced in a timely way. It was not clear whether the observed peak in calls reflected a true increase in influenza or whether it was the result of an increase in calls over the Christmas/Millennium holiday period due to more difficulty in accessing other services. The ability to assess the proportion of calls made directly by, or on behalf of, each age group will be of vital importance in interpreting seasonal respiratory disease.