Improving early epidemiological assessment of emerging Aedes-transmitted epidemics using historical data

Julien Riou; Chiara Poletto; Pierre-Yves Boëlle

Yet little is known regarding the comparative epidemiology of diseases in the same or similar places and on the condition where transportability can be assumed. For inuenza, it has been reported that the reproduction ratios in two successive u pandemics (1889 and 1918) showed substantial correlation (r = 0.62) in the same US cities, even years apart [54] . For Aedes -transmitted diseases, comparisons of ZIKV and dengue virus outbreaks [55] and of ZIKV with CHIKV outbreaks [44] in the same locations have highlighted similarities in the epidemic dynamics. In any case, careful consideration of all the factors that may inuence transmission and reporting is needed. For example, contrary to CHIKV, some cases of sexual transmission have been reported for ZIKV [56, 57] . Yet, no epidemics were seen in locations without enough Aedes mosquitoes, as for example in metropolitan France, despite the introductions of several hundreds ZIKV infected cases [58] . This justies the use of CHIKV epidemic data to provide prior information on ZIKV in the epidemic context considered here. More generally, documenting, analyzing and comparing more systematically past epidemics [59] is necessary to provide the data required to derive prior information. In particular, informed with epidemiological records of the recent CHIKV and ZIKV epidemics, our approach could be applied to potential future emergences of other Aedes -transmitted diseases such as Mayaro virus [60] , Ross River virus [61] or Usutu virus [62] once transportability is deemed plausible.