[London, UK/ Medicine] - The UK Health Protection Agency (HPA) has established enhanced disease surveillance systems, including new arrangements for real-time syndromic surveillance of illness in the population at large for the London 2012 Olympic and Paralympic Games.
Syndromic surveillance is the real-time (or near real-time) collection, analysis, interpretation and dissemination of health-related data to enable the early identification of a public health threat. The Agency′s Real-time Syndromic Surveillance Team (ReSST) regularly monitors disease outbreak using a range of systems:
- NHS Direct Syndromic Surveillance System monitors syndromic indicators (cold/flu; fever; cough; difficulty breathing; rash; diarrhoea; vomiting; eye problems; lumps; double vision) in calls to NHS Direct in England and Wales;
- NHS24 syndromic surveillance system monitors syndromic calls each day across Scotland;
- QSurveillance National Syndromic Surveillance System monitors 30 clinical indicators, based on aggregated Read codes in 3400 GP practices covering 24 million patients;
- Royal College of General Practitioners Weekly Returns Service (RCGP WRS) monitors 100 sentinel GP practices for a range of acute illnesses and can integrate microbiological testing.
The ReSST brought on stream in April an enhanced syndromic surveillance service that includes new reporting mechanisms and an upgrading of pre-existing ones. The two principal enhancements have been:
- a new Emergency Department Syndromic Surveillance System (EDSSS), which is providing real-time monitoring of attendance data from a sentinel network of emergency departments;
- a newly developed GP Out-of-Hours/Unscheduled Care Syndromic Surveillance System (GPOOHSS) system which is providing daily reports of patients presenting to out-of-hours services, and walk-in centres.
The EDSSS, developed with the the College of Emergency Medicine, provides for the first time in the UK a public health surveillance system for routine monitoring of more severe presentations of acute disease than was previously possible through the existing GP and NHS Direct syndromic surveillance systems. Surveillance data from the GPOOHSS scheme now cover evenings, nights, weekends and bank holidays, complementing the ‘in-hours′ data previously available. The HPA has also set up a enhanced rapid diagnostic service covering respiratory, gastrointestinal and waterborne diseases at its laboratories around England.
An automated disease outbreak detection system has been used by the HPA since the early 1990′s. The system is based on a set of algorithms known as Robust Poisson Regression (RPR). Outbreak detection starts with the detection of an unusual number of reported cases of a particular infection in a given time and space. Computer programs are used to compare the observed number of cases with expected values. When an increase is detected, the program raises an alert, which epidemiologists assess to determine if further investigation is warranted. If an outbreak is confirmed, further investigations follow and control measures are taken.
Paddy Farrington, Professor of Statistics at The Open University, began work on the outbreak detection system while he was at the Health Protection Agency (HPA) in the early 1990s and is working on a new version. “Much interest in the use of statistical surveillance systems has been driven by concerns over bio-terrorism, the emergence of new pathogens like SARS and swine flu, and the persistent public health problems of infectious disease outbreaks,” said Professor Farrington. “Our system is the first to offer a comprehensive way to detect such outbreaks. A challenge in designing large multiple outbreak detection systems is to control the proportion of false alarms without impairing the detection of genuine outbreaks. Through improvements to the existing system, we managed to reduce the number of false alarms by 50% without impairing performance.”
Professor Farrington told BJHC, “The data used by this particular system comes from laboratories, many of them based in hospitals, throughout England and Wales. These receive samples (eg fecal samples) sent by clinicians for analysis and the information on infectious pathogens identified in these samples are forwarded electronically to the Centre for Infections at the HPA in London. The system will be run each day during the period of the Olympics, rather than weekly as occurs normally.”
These new and enhanced surveillance systems will also form an important legacy of the Games, providing England and Wales with one of the most comprehensive public health-based syndromic surveillance programmes in the world. [hw]
The Health Protection Agency real-time syndromic surveillance web pages