Epidemic intelligence activities during major international incidents involving emerging infections

Abstract

Purpose: To review and describe sources of information used by Public Health England's epidemic intelligence (EI) system during the Ebola virus disease (EVD) outbreak in West Africa, and Zika virus outbreak in the Americas. Outputs from this analysis will be used to refine EI practices to inform risk assessments and policy during future major incidents. Methods & Materials: Since 2003, Public Health England has maintained a manual event-based surveillance system of mostly open source data for detecting and monitoring incidents involving emerging infectious diseases. Where possible, initial alerting sources for data (eg media) are validated by obtaining a definitive information source (eg national authorities). Data collated during the West African EVD and the Americas Zika virus outbreaks were analysed to assess the relative importance of different sources for information gathering. Results: EI activities during these two incidents resulted in the collection of 5,072 and 2,631 entries for EVD and Zika virus respectively, comprising 41% and 18% of total EI entries recorded during their respective outbreak periods. For EVD and Zika virus, 51% and 33% of entries respectively had different initial alerting sources compared to definitive information sources. Of these, aggregate open-source surveillance websites (eg ProMED) were the principal sources of initial alerts (40% for EVD and 46% for Zika virus). For EVD, 41% of definitive information came from media outlets, 19% from the World Health Organization (WHO), 12% each from scientific journals and national authorities. For Zika virus, 33% of definitive information came from scientific journals, 29% from media outlets, 21% from national authorities, and 13% from WHO. Conclusion: Although resource intensive, EI activities are an important feature of national preparedness to inform risk assessments, policy and guidance during major infectious disease incidents. While national and international authorities are recognised as principal sources of EI, aggregate surveillance systems, traditional media outlets, and scientific journals remain essential sources of information during international incidents. This analysis highlights the importance of comprehensive but flexible EI systems, particularly for incidents caused by emerging infectious agents. In particular, it emphasises the utility of manual EI systems readily adaptable to the specific requirements of individual incidents.