Interactions between timing and transmissibility explain diverse flavivirus dynamics in Fiji.

Zika virus (ZIKV) has caused large, brief outbreaks in isolated populations, however ZIKV can also persist at low levels over multiple years. The reasons for these diverse transmission dynamics remain poorly understood. In Fiji, which has experienced multiple large single-season dengue epidemics, there was evidence of multi-year transmission of ZIKV between 2013 and 2017. To identify factors that could explain these differences in dynamics between closely related mosquito-borne flaviviruses, we jointly fit a transmission dynamic model to surveillance, serological and molecular data. We estimate that the observed dynamics of ZIKV were the result of two key factors: strong seasonal effects, which created an ecologically optimal time of year for outbreaks; and introduction of ZIKV after this optimal time, which allowed ZIKV transmission to persist over multiple seasons. The ability to jointly fit to multiple data sources could help identify a similar range of possible outbreak dynamics in other settings

First B-dot measurements in the RAID device, an alternative negative ion source for DEMO neutral beams

International audienceAs a new concept of Neutral Beam Injectors (NBI) for DEMO-like reactors, SIPHORE (IRFM, CEA, in France) expects to extract negative deuterium ions and photo-neutralize the accelerated D-. The Swiss Plasma Center (SPC) of EPFL is involved in this project by developing an innovative helicon source, which could provide the adequate D 2 negative ion blade-shaped plasma, in terms of density and homogeneity along the axial direction. In the Resonant Antenna Ion Device (RAID), the test bed, a helicon wave is sustained by a resonant antenna plasma source at 13.56 MHz (input power ≤ 10 kW), connected to a cylindrical vacuum chamber (1.5 m long, 0.4 m diameter) and is surrounded by 6 Helmholtz coils, providing a DC magnetic field up to 800 G on axis. To characterize the helicon wave propagation, RAID has been recently equipped with a three-axis magnetic probe (B-dot). The paper describes the RAID experiment and its helicon source, including a 3D characterization of density and temperature, together with the B-dot design and calibration. It presents measurements of helicon wave propagation; in typical H 2 plasmas (0.3 Pa), preliminary results show a helicon wave right-handed polarized with a wavelength of approximately 240 mm