Long-term persistence of monotypic dengue transmission in small size isolated populations, French Polynesia, 1978-2014

Abstract

Understanding the transition of epidemic to endemic dengue transmission remains a challenge in regions where serotypes co-circulate and there is extensive human mobility. French Polynesia, an isolated group of 117 islands of which 72 are inhabited, distributed among five geographically separated subdivisions, has recorded mono-serotype epidemics since 1944, with long inter-epidemic periods of circulation. Laboratory confirmed cases have been recorded since 1978, enabling exploration of dengue epidemiology under monotypic conditions in an isolated, spatially structured geographical location. A database was constructed of confirmed dengue cases, geolocated to island for a 35-year period. Statistical analyses of viral establishment, persistence and fade-out as well as synchrony among subdivisions were performed. Seven monotypic and one heterotypic dengue epidemic occurred, followed by low-level viral circulation with a recrudescent epidemic occurring on one occasion. Incidence was asynchronous among the subdivisions. Complete viral die-out occurred on several occasions with invasion of a new serotype. Competitive serotype replacement has been observed previously and seems to be characteristic of the South Pacific. Island population size had a strong impact on the establishment, persistence and fade-out of dengue cases and endemicity was estimated achievable only at a population size in excess of 175 000. Despite island remoteness and low population size, dengue cases were observed somewhere in French Polynesia almost constantly, in part due to the spatial structuration generating asynchrony among subdivisions. Long-term persistence of dengue virus in this group of island populations may be enabled by island hopping, although could equally be explained by a reservoir of sub-clinical infections on the most populated island, Tahiti.

The Absence of Yellow Fever in Asia: History, Hypotheses, Vector Dispersal, Possibility of YF in Asia, and Other Enigmas

“…aegypti regarding the duration of persistence in urban areas. For the four serotypes of DENV, the probability of the establishment of viral persistence in a fixed, urban area for several years or longer increases when human population size exceeds a minimal population size, even when seroprevalence of homologous or cross-reactive antibodies is still considerable [169,170]. However, CHIKV and ZIKV disappear quickly after causing an extensive outbreak in urban areas even when large proportions of populations still remain susceptible but reappear in other locations unpredictably, jumping from one location to another [171][172][173].…”

Reconstructing long-term dengue virus immunity in French Polynesia

“…The islands constituting French Polynesia are grouped into five administrative subdivisions: Windward, Leeward, Marquesas, Austral, and Tuamotu-Gambier (Fig.1). Since March 1975, Institut Louis Malardé in French Polynesia has received samples of suspected Dengue fever cases over the islands (Teissier et al 2020). These samples have been analysed with different laboratory techniques, such as Haemagglutination Inhibition Assay (between 1975 and 1988), ELISA-IgM (1986-2003), isolation of DENV on mosquito C6/36 cell culture (1984-2005), and Reverse transcriptase Polymerase Chain Reaction (since 2000).…”

“…The j-th time period is labelled T j ( j = 1, …, J ), whose start time and duration are denoted t j and Δt j , respectively. Since epidemics are mono-serotypic (Teissier et al 2020), there is only one serotype with a non-null FOI at any given time. Data are also available before 1979 but they are more limited (Aubry and Cao-Lormeau 2019).…”

Integrating Social Sciences to Mitigate Against Covid

“…At the metapopulation scale, local patches are colonized at a rate governed by immigration of the invasive organism, but which then may become extinct locally. Metapopulation approaches, originally developed for ecological systems, have been applied to infectious diseases (Grenfell and Harwood 1997;Teissier et al 2020). A key feature of the metapopulation approach is that while local populations of hosts and pathogens may be unstable, with for example local extinction, loosely connected populations, at whatever scale, may enable pathogen survival at the global scale.…”