title: Influenza seasonality in Madagascar: the mysterious African free-runner.
abstract: BACKGROUND
  The seasonal drivers of influenza activity remain debated in tropical settings where epidemics are not clearly phased. Antananarivo is a particularly interesting case study because it is in Madagascar, an island situated in the tropics and with quantifiable connectivity levels to other countries.
  
  
  OBJECTIVE
  We aimed at disentangling the role of environmental forcing and population fluxes on influenza seasonality in Madagascar.
  
  
  METHODS
  We compiled weekly counts of laboratory-confirmed influenza-positive specimens for the period 2002 to 2012 collected in Antananarivo, with data available from sub-Saharan countries and countries contributing most foreign travelers to Madagascar. Daily climate indicators were compiled for the study period.
  
  
  RESULTS
  Overall, influenza activity detected in Antananarivo predated that identified in temperate Northern Hemisphere locations. This activity presented poor temporal matching with viral activity in other countries from the African continent or countries highly connected to Madagascar excepted for A(H1N1)pdm09. Influenza detection in Antananarivo was not associated with travel activity and, although it was positively correlated with all climatic variables studied, such association was weak.
  
  
  CONCLUSIONS
  The timing of influenza activity in Antananarivo is irregular, is not driven by climate, and does not align with that of countries in geographic proximity or highly connected to Madagascar. This work opens fresh questions regarding the drivers of influenza seasonality globally particularly in mid-latitude and less-connected regions to tailor vaccine strategies locally.
authors.affiliation: Fogarty International Center, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Wladimir Jimenez
authors.initials: WJ
authors.lastname: Alonso
authors.forename: Julia
authors.initials: J
authors.lastname: Guillebaud
authors.forename: Cecile
authors.initials: C
authors.lastname: Viboud
authors.forename: Norosoa Harline
authors.initials: NH
authors.lastname: Razanajatovo
authors.forename: Arnaud
authors.initials: A
authors.lastname: Orelle
authors.forename: Steven Zhixiang
authors.initials: SZ
authors.lastname: Zhou
authors.forename: Laurence
authors.initials: L
authors.lastname: Randrianasolo
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Heraud
mesh_terms: D002980:Climate; D058872:Epidemics; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D053122:Influenza A Virus, H3N2 Subtype; D009981:Influenza B virus; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D008270:Madagascar / Q000453:epidemiology; D012621:Seasons; D018571:Sentinel Surveillance; D013997:Time Factors; D014195:Travel
chemical_list: D007252:Influenza Vaccines
keywords: Influenza; Madagascar; population connectivity; seasonality; time series; viral migration