Pilot scheme for monitoring sickness absence in schools during the 2006/07 winter in England: can these data be used as a proxy for influenza activity?

During influenza epidemics, school-aged children are amongst the first affected patients. They frequently then spread the virus within their families. Recognising influenza activity in schools may therefore be an important indicator of early activity in the wider community. During 2005/06, influenza B was associated with high levels of morbidity in school-children and over 600 schools outbreaks were reported to the Health Protection Agency by local Health Protection Units. While it is not possible to directly monitor influenza in schools, the feasibility and validity of using sentinel school absenteeism data, as a proxy for influenza in the community can be investigated. From week 02/07 to 20/07, eight primary and three secondary schools from five HPA regions were able, via the Department of Health-funded Health Protection Informatics website, to report daily electronic registration data, relating to absenteeism due to illness. Aggregated absenteeism data due to illness peaked the same week as indices for the age group comparable to that used by the Royal College for General Practitioners and NHS Direct schemes. When illness-defined absenteeism data was stratified into primary and secondary schools, absence in primary schools peaked one week before that in secondary schools and the established schemes for all ages. The start time of the study meant that initial increases in activity could not be measured. These encouraging results justify expanding this sentinel scheme to collect more rigorous evidence of the usefulness of absenteeism as a proxy for influenza activity and a tool to inform policy and trigger local responses.