title: Alarm Variables for Dengue Outbreaks: A Multi-Centre Study in Asia and Latin America.
abstract: BACKGROUND
  Worldwide, dengue is an unrelenting economic and health burden. Dengue outbreaks have become increasingly common, which place great strain on health infrastructure and services. Early warning models could allow health systems and vector control programmes to respond more cost-effectively and efficiently.
  
  
  RESULTS
  The Shewhart method and Endemic Channel were used to identify alarm variables that may predict dengue outbreaks. Five country datasets were compiled by epidemiological week over the years 2007-2013. These data were split between the years 2007-2011 (historic period) and 2012-2013 (evaluation period). Associations between alarm/ outbreak variables were analysed using logistic regression during the historic period while alarm and outbreak signals were captured during the evaluation period. These signals were combined to form alarm/ outbreak periods, where 2 signals were equal to 1 period. Alarm periods were quantified and used to predict subsequent outbreak periods. Across Mexico and Dominican Republic, an increase in probable cases predicted outbreaks of hospitalised cases with sensitivities and positive predictive values (PPV) of 93%/ 83% and 97%/ 86% respectively, at a lag of 1-12 weeks. An increase in mean temperature ably predicted outbreaks of hospitalised cases in Mexico and Brazil, with sensitivities and PPVs of 79%/ 73% and 81%/ 46% respectively, also at a lag of 1-12 weeks. Mean age was predictive of hospitalised cases at sensitivities and PPVs of 72%/ 74% and 96%/ 45% in Mexico and Malaysia respectively, at a lag of 4-16 weeks.
  
  
  CONCLUSIONS
  An increase in probable cases was predictive of outbreaks, while meteorological variables, particularly mean temperature, demonstrated predictive potential in some countries, but not all. While it is difficult to define uniform variables applicable in every country context, the use of probable cases and meteorological variables in tailored early warning systems could be used to highlight the occurrence of dengue outbreaks or indicate increased risk of dengue transmission.
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.|UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR), Geneva, Switzerland.
authors.forename: Leigh R
authors.initials: LR
authors.lastname: Bowman
authors.affiliation: Ministry of Health, Mexico City, Mexico.
authors.forename: Gustavo S
authors.initials: GS
authors.lastname: Tejeda
authors.affiliation: Ministry of Health, Brasilia, Brazil.
authors.forename: Giovanini E
authors.initials: GE
authors.lastname: Coelho
authors.affiliation: Ministry of Health, Kuala Lumpur, Malaysia.
authors.forename: Lokman H
authors.initials: LH
authors.lastname: Sulaiman
authors.affiliation: Ministry of Health, Kuala Lumpur, Malaysia.
authors.forename: Balvinder S
authors.initials: BS
authors.lastname: Gill
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: McCall
authors.affiliation: UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR), Geneva, Switzerland.
authors.forename: Piero L
authors.initials: PL
authors.lastname: Olliaro
authors.affiliation: UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR), Geneva, Switzerland.|Institute of Public Health, University of Heidelberg, Heidelberg, Germany.
authors.forename: Silvia R
authors.initials: SR
authors.lastname: Ranzinger
authors.affiliation: Pasteur Institute, Ho Chi Minh City, Vietnam.
authors.forename: Luong C
authors.initials: LC
authors.lastname: Quang
authors.affiliation: Ministry of Health, Santo Domingo, Dominican Republic.
authors.forename: Ronald S
authors.initials: RS
authors.lastname: Ramm
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.|UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR), Geneva, Switzerland.
authors.forename: Axel
authors.initials: A
authors.lastname: Kroeger
authors.affiliation: UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR), Geneva, Switzerland.|University of Gothenburg, Gothenburg, Sweden.
authors.forename: Max G
authors.initials: MG
authors.lastname: Petzold
mesh_terms: D001208:Asia; D003715:Dengue / Q000453:epidemiology*; D004196:Disease Outbreaks; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007843:Latin America; D015233:Models, Statistical; D012621:Seasons