Abstract

In French Polynesia, like in most tropical and subtropical regions of the world, dengue fever is still a major public health concern. Since the middle of the last century, French Polynesia has experienced twelve epidemics caused by all four dengue virus serotypes. Nine of these epidemics occurred after the introduction of a new viral strain, originated from the Americas, South East Asia or the Pacific : DEN-1 (1944,1975,1988,2001), DEN-2 (1971, 1996), DEN-3 (1964, 1989), DEN-4 (1979). The three other epidemics were caused by strains already implicated in the previous outbreak : DEN-3 (1969), DEN-4 (1985) and DEN-1 (2006). The dynamic of dengue epidemics in French Polynesia seems to be driven by particular events. The introduction of a dengue that hasn't circulated for years in the area causes an epidemic. After the outbreak, the virus can persist for years (endemic strain), however, if a new serotype is introducted and causes a new epidemic, the endemic strain will be totally replaced in few months (ersistent co-circulation of multiple serotypes has never been reported). In the absence of new viral introduction, the endemic strain can re-emerge and cause a second dengue outbreak five to six years later. By collecting all available data related to past and recent dengue epidemics (epidemic duration, number of cases, epidemic severity, season of outbreak, attack rates per age...), we investigated wether the epidemiological pattern of dengue in French Polynesia can be related to the particular geographical (insularity and high distance from continental countries), eco-biological (climate, presence of endemic vectors) and sociological contexts (relatively stable human flows). Because the Pacific Island Countries (PICs) share most of the French Polynesian particularities, the identification of the events and factors characterizing the epidemiology of dengue in French Polynesia would contribute to a better understanding of dengue epidemiology in the PICs.