Syndromic surveillance for Ebola virus disease in ...

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Headaches, vomiting, anorexia / loss of appetite, diarrhoea, lethargy, stomach pain, aching muscles or joints, difficulty swallowing, breathing difficulties, hiccup.
Syndromic surveillance for Ebola virus disease in emergency wards George W. Rutherford, M.D. University of California, San Francisco

Syndromic surveillance • An early warning system that aims to collect information regarding nonspecific health indicators (e.g. symptoms) prior to the development of disease, diagnosis, and reporting to health officials • Goal is to identify outbreaks early for rapid understanding of the threat and response mobilization • Uses existing health data in real time • Of particular importance at detecting acts of bioterrorism

CDC definition of syndromic surveillance “an investigational approach where health department staff, assisted by automated data acquisition and generation of statistical alerts, monitor disease indicators in real-time or near real-time to detect outbreaks of disease earlier than would otherwise be possible with traditional public health methods.””

Early detection of a condition by syndromic surveillance

Data sources for syndromic surveillance

Syndromic case definitions • • • • •

ILI and SARI Chronic fatigue syndrome AIDS Acute flaccid paralysis SARS (now SARS CoV)

New York City syndromic surveillance systems • Diarrheal disease surveillance (1995) • Emergency medical services ambulance dispatch calls (1998) • Emergency department visits (2001) • Retail pharmacy sales (2002) • Worker absenteeism (2001)

Diarrheal disease surveillance • Designed to detect substantial outbreaks of diarrhea, especially waterborne pathogens • Tracks three indicators: – Diarrhea at nursing homes – Submission of stool specimens to laboratories – Over the counter pharmacy sales

WHO case definition of EVD Suspected case Any person, alive or dead, suffering or having suffered from a sudden onset of high fever and having had contact with: – a suspected, probable or confirmed Ebola or Marburg case – a dead or sick animal (for Ebola) – a mine (for Marburg)

OR: any person with sudden onset of high fever AND at least three of the following symptoms: – Headaches, vomiting, anorexia / loss of appetite, diarrhoea, lethargy, stomach pain, aching muscles or joints, difficulty swallowing, breathing difficulties, hiccup

OR: any person with inexplicable bleeding OR: any sudden, inexplicable death.

Problems with syndromic surveillance • Not meant to substitute for specific etiologic diagnosis • Non-specific case definitions – Overascertainment of cases, WHO case definition is basically fever plus systemic symptoms – Overuse of quarantine (and exposure to potentially infectious patients) – Malaria, typhoid, etc. not getting treated

• Lack of geographical or temporal specificity

Examples of syndromic surveillance systems

Henning KJ. What is syndromic surveillance?. In: CDC. Syndromic Surveillance: Reports from a National Conference, 2003. MMWR 2004;53 (Suppl):7-11.

Emergency Medical Services ambulance dispatch calls • Calls are categorized into 52 call types • Main outcome of system is calls related to influenza-like symptoms – Evaluation showed that the system detected influenza epidemic 2-3 weeks prior to detection through traditional system

• Intent to aid in detecting bioterrorism

Emergency department visits • To detect acts of bioterrorism • Electronic system of data from 48 hospitals in NYC (~86% ED visits) • Collects information from all visits: – Date and time of visit – Age – Sex – Residential zip code – Chief complaint (free text) – MR number (not all hospitals)

Retail pharmacy sales • Collects electronic data from 248 pharmacies (~30% city total) • Daily report of the number of non prescription medications sold by drug name and pharmacy • Focus on influenza- and diarrheal-related medications

Worker absenteeism • Data from a single employer with multiple locations – 15,000 employees

• Reasons for absence categorized by computer algorithm: – Fever/influenza – Gastrointestinal – Upper respiratory infection