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ISDS 2016 Conference Abstracts

The importance of age-specific data in routine 
syndromic surveillance
Roger Morbey*, Alex J. Elliot and Gillian E. Smith
Public Health England, Birmingham, United Kingdom

Objective
To investigate whether aberration detection methods for syndromic 

surveillance would be more useful if data were stratified by age band.

Introduction
When monitoring public health incidents using syndromic 

surveillance systems, Public Health England (PHE) uses the age 
of the presenting patient as a key indicator to further assess the 
severity, impact of the incident, and to provide intelligence on the 
likely cause. However the age distribution of cases is usually not 
considered until after unusual activity has been identified in the all-
ages population data. We assessed whether monitoring specific age 
groups contemporaneously could improve the timeliness, specificity 
and sensitivity of public health surveillance.

Methods
First, we examined a wide range of health indicators from the PHE 

syndromic surveillance systems to identify for further study those 
with the greatest seasonal variation in the age distribution of cases. 
Secondly, we examined the identified indicators to ascertain whether 
any age bands consistently lagged behind other age bands. Finally, 
we applied outbreak detection methods retrospectively to age specific 
data, identifying periods of increased activity that were only detected 
or detected earlier when age-specific surveillance was used.

Results
Seasonal increases in respiratory indicators occurred first in 

younger age groups, with increases in children under 5 providing 
early warning of subsequent increases occurring in older age groups. 
Also, we found age specific indicators improved the specificity of 
surveillance using indicators relating to respiratory and eye problems; 
identifying unusual activity that was less apparent in the all-ages 
population.

Conclusions
Routine surveillance of respiratory indicators in young children 

would have provided early warning of increases in older age groups, 
where the burden on health care usage, e.g. hospital admissions, is 
greatest. Furthermore this cross-correlation between ages occurred 
consistently even though the age distribution of the burden of 
respiratory cases varied between seasons. Age specific surveillance 
can improve sensitivity of outbreak detection although all-age 
surveillance remains more powerful when case numbers are low.

Keywords
Syndromic; Surveillance; Age

Acknowledgments
The authors are partly funded by the National Institute for Health Research 
(NIHR) Health Protection Research Unit in Emergency Preparedness and 
Response. The views expressed are those of the authors and not necessarily 
those of the National Health Service, the NIHR, the Department of Health 
or Public Health England.

*Roger Morbey
E-mail: roger.morbey@phe.gov.uk

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 9(1):e24, 2017