title: Dengue disease outbreak definitions are implicitly variable.
abstract: Infectious diseases rarely exhibit simple dynamics. Outbreaks (defined as excess cases beyond response capabilities) have the potential to cause a disproportionately high burden due to overwhelming health care systems. The recommendations of international policy guidelines and research agendas are based on a perceived standardised definition of an outbreak characterised by a prolonged, high-caseload, extra-seasonal surge. In this analysis we apply multiple candidate outbreak definitions to reported dengue case data from Brazil to test this assumption. The methods identify highly heterogeneous outbreak characteristics in terms of frequency, duration and case burden. All definitions identify outbreaks with characteristics that vary over time and space. Further, definitions differ in their timeliness of outbreak onset, and thus may be more or less suitable for early intervention. This raises concerns about the application of current outbreak guidelines for early warning/identification systems. It is clear that quantitatively defining the characteristics of an outbreak is an essential prerequisite for effective reactive response. More work is needed so that definitions of disease outbreaks can take into account the baseline capacities of treatment, surveillance and control. This is essential if outbreak guidelines are to be effective and generalisable across a range of epidemiologically different settings.
authors.affiliation: Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK. Electronic address: oliver.brady.zoo@gmail.com.
authors.forename: Oliver J
authors.initials: OJ
authors.lastname: Brady
authors.affiliation: Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK; Fogarty International Center, National Institutes of Health, Bethesda, MD, USA; Sanaria Institute for Global Health and Tropical Medicine, Rockville, MD, USA. Electronic address: smitdave@gmail.com.
authors.forename: David L
authors.initials: DL
authors.lastname: Smith
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, MD, USA; Department of Entomology and Nematology, University of California, Davis, CA, USA. Electronic address: twscott@ucdavis.edu.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Scott
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, MD, USA; The Wellcome Trust Centre for Human Genetics, Roosevelt Drive, Oxford OX3 7BN, UK. Electronic address: simon.i.hay@gmail.com.
authors.forename: Simon I
authors.initials: SI
authors.lastname: Hay
mesh_terms: D001938:Brazil / Q000453:epidemiology; D003715:Dengue / Q000453:epidemiology*; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D006801:Humans; D008962:Models, Theoretical; D011159:Population Surveillance / Q000379:methods*
keywords: Decision-making; Dengue; Outbreak; Policy; Response