Enteroviruses (EV) are the most frequent cause of acute meningitis worldwide, and regularly responsible for outbreaks. Human parechoviruses (PeV) are associated with sepsis and meningitis in young ...infants. In Mayotte, a French department located in the Comoros archipelago, EVs and PeVs are not part of the routine screening of cerebrospinal fluids (CSFs) of patients with meningitis. Consequently, no data is available on EV or PeV epidemiology.
Assess the need for EV and PeV diagnosis in Mayotte.
CSFs collected between March and June 2019 from patients addressed to Mayotte Hospital were retrospectively screened for EV and PeV by PCR. If positive for EV, genotyping was attempted.
EV and PeV RT-PCR were performed on 122/263 (46%) CSFs (45 adults, 77 children). EV meningitis was diagnosed in 16/77 children (21%) with a median age of 32 days (8–62). One 30-days-aged infant presented with a PeV infection. Fever was reported in 94% cases (16/17), followed by gastrointestinal disorders in 29% cases (5/17). EV genotyping achieved identification for 10/16 (63%) EV-positive samples. Four different EV types were identified: Echovirus 16 (E-16, n = 6), EV-B100 (n = 2), and E-14 and E-18 (n = 1, each).
EV/PeV prevalence of 14% highlights the importance of implementing this diagnosis which can impact duration of hospitalization and administration of antibiotics thus reducing risk of antimicrobial resistance. Surveillance of circulating EV types is needed to understand the range of enteroviruses detected in meningitis cases in places that have been underrepresented in enterovirus surveillance studies.
SUMMARY
The brutal onset of seismicity offshore Mayotte island North of the Mozambique Channel, Indian Ocean, that occurred in May 2018 caught the population, authorities and scientific community off ...guard. Around 20 potentially felt earthquakes were recorded in the first 5 d, up to magnitude Mw 5.9. The scientific community had little pre-existing knowledge of the seismic activity in the region due to poor seismic network coverage. During 2018 and 2019, the MAYOBS/REVOSIMA seismology group was progressively built between four French research institutions to improve instrumentation and data sets to monitor what we know now as an on-going exceptional submarine basaltic eruption. After the addition of 3 medium-band stations on Mayotte island and 1 on Grande Glorieuse island in early 2019, the data recovered from the Ocean Bottom Seismometers were regularly processed by the group to improve the location of the earthquakes detected daily by the land network. We first built a new local 1-D velocity model and established specific data processing procedures. The local 1.66 low VP/VS ratio we estimated is compatible with a volcanic island context. We manually picked about 125 000 P and S phases on land and sea bottom stations to locate more than 5000 events between February 2019 and May 2020. The earthquakes outline two separate seismic clusters offshore that we named Proximal and Distal. The Proximal cluster, located 10 km offshore Mayotte eastern coastlines, is 20–50 km deep and has a cylindrical shape. The Distal cluster start 5 km to the east of the Proximal cluster and extends below Mayotte's new volcanic edifice, from 50 to 25 km depth. The two clusters appear seismically separated, however our data set is insufficient to firmly demonstrate this.
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•A comprehensive multi-locus phylogeny of Echinophyllia and Oxypora is presented.•Three independent species delimitation approaches (ABGD, PTP and, GMYC) are used.•Discordance between ...traditional morphospecies and molecular lineages is found.•Two new species of Echinophyllia are described.
Scleractinian corals are affected by environment-induced phenotypic plasticity and intraspecific morphological variation caused by genotype. In an effort to identify new strategies for resolving this taxonomic issue, we applied a molecular approach for species evaluation to two closely related genera, Echinophyllia and Oxypora, for which few molecular data are available. A robust multi-locus phylogeny using DNA sequence data across four loci of both mitochondrial (COI, ATP6-NAD4) and nuclear (histone H3, ITS region) origin from 109 coral colonies was coupled with three independent putative species delimitation methods based on barcoding threshold (ABGD) and coalescence theory (PTP, GMYC). Observed overall congruence across multiple genetic analyses distinguished two traditional species (E. echinoporoides and O. convoluta), a species complex composed of E. aspera, E. orpheensis, E. tarae, and O. glabra, whereas O. lacera and E. echinata were indistinguishable with the sequenced loci. The combination of molecular species delimitation approaches and skeletal character observations allowed the description of two new reef coral species, E. bulbosa sp. n. from the Red Sea and E. gallii sp. n. from the Maldives and Mayotte. This work demonstrated the efficiency of multi-locus phylogenetic analyses and recently developed molecular species delimitation approaches as valuable tools to disentangle taxonomic issues caused by morphological ambiguities and to re-assess the diversity of scleractinian corals.
In May 2018, a seismically quiet region of the Indian Ocean awoke. More than 130 magnitude 4+ earthquakes were recorded in the first month, including a MW 5.9 event on May 15th, 2018. This seismic ...activity was later identified as being related to an exceptional underwater volcanic eruption offshore Mayotte island, which had emitted more than 6.5 km3 of lava by the time of writing. To better constrain the geodynamic processes responsible for the seismic and volcanic activity, a new network of ocean-bottom seismometers and land stations has been deployed around the seismically active region since February 2019. We present here an improved 1D velocity model for the active area and relocations of manually-picked earthquakes using this new model. The best-constrained events image detailed structures within two clusters of seismic activity east of Mayotte. The westernmost, proximal cluster, close to Mayotte's Petite-Terre island, has a “donut” shape horizontally and an “hourglass” shape in depth. The events distribution suggests the presence of a magma reservoir at around 27 km depth, with earthquakes focused along its sides, and a collapsing system underneath, related to the drainage of another, deeper magma storage zone. The distal cluster, focused 30–50 km offshore of Petite-Terre island, highlights the propagation of a dike between 45 and 25 km depth, aligned towards the new volcanic activity on the seafloor. We interpret this cluster as the fluid pathway towards the new volcano and nearby active seafloor lava fields. The improved velocity model also permits more robust daily monitoring of the seismicity using land stations, allowing local authorities to better assess seismic and volcanic hazards and to communicate them to the island's population.
•We develop a new local 1D velocity model for Mayotte.•The locations of the detected earthquakes are significantly improved.•The earthquakes' distribution images the active structures of the magmatic system.•Daily monitoring is now more robust, helping hazard assessments and communication.
Following an unprecedented seismic activity that started in May 2018, a new volcanic edifice, now called Fani Maoré, was constructed on the ocean floor 50 km east of the island of Mayotte (Indian ...Ocean). This volcano is the latest addition to a volcanic chain characterized by an alkaline basanite-to-phonolite magmatic differentiation trend. Here, we performed viscosity measurements on five silicate melts representative of the East-Mayotte Volcanic Chain compositional trend: two basanites from Fani Maoré, one tephriphonolite and two phonolites from different parts of the volcanic chain. A concentric cylinder viscometer was employed at super-liquidus conditions between 1500 K and 1855 K and a creep apparatus was used for measuring the viscosity of the undercooled melts close to the glass transition temperature in the air. At super-liquidus temperatures, basanites have the lowest viscosity (0.11–0.34 to 0.99–1.16 log10 Pa⸱s), phonolites the highest (1.75–1.91 to 3.10–3.89 log10 Pa⸱s), while the viscosity of the tephriphonolite falls in between (0.89–1.97 log10 Pa⸱s). Near the glass transition, viscosity measurements were performed for one phonolite melt because obtaining pure glass samples for the basanite and tephriphonolite compositions was unsuccessful. This is due to the formation of nanolites upon quench as evidenced by Raman spectroscopy. The phonolite viscosity ranges from of 10.19 log10 Pa⸱s at 1058 K to 12.30 log10 Pa⸱s at 986 K. Comparison with existing empirical models reveals an underestimation of 1.2 to 2.0 log units at super-liquidus and undercooled temperatures, respectively, for the phonolite. This emphasizes (i) the lack of data falling along the alkaline basanite-to-phonolite magmatic differentiation trend to calibrate empirical models, and (ii) the complexity of modeling viscosity variations as a function of temperature and chemical composition for alkaline compositions. The new measurements indicate that, at eruptive temperatures between 1050 °C and 1150 °C (1323–1423 K), the oxidized, anhydrous, crystal-free and bubble-free basanite melt have a viscosity around 2.6 log10 Pa⸱s. In contrast, the anhydrous phonolite crystal- and bubble-free melt would have a viscosity around 6–10 log10 Pa⸱s at expected eruptive temperatures, from 800 to 1000 °C (1073–1273 K). Considering that both basanite and phonolite lavas from the Mayotte submarine volcanic chain contain <6% crystals and a significant amount of water (1-2.3 wt% and 0.8-1.2 wt%, respectively), such viscosity values are probably upper limits. The new viscosity measurements are essential to define eruptive models and to better understand the storage and transport dynamics of Comoros Archipelago magmas, and of alkaline magmas in general, from the source to the surface.
•Pure liquid viscosity measurements are performed on submarine melts from the basanite - phonolite trend.•Super-liquidus viscosity (log10 Pas) is 0.11-1.16 for basanite, 0.89 –1.97 for tephriphonolite and 1.75-3.89 for phonolite.•A discrepancy is revealed by comparing experimental measurements and parametric viscosity models.•The effect of water at the eruptive temperatures for such compositions is explored.
From November 2018 through July 2019, an outbreak of Rift Valley fever in humans occurred in Mayotte, France; 142 cases were confirmed. Exposure to animals or their biological fluid was reported by ...73% of patients. Health authorities have been implementing control measures, including veterinary surveys, vector control interventions, and prevention measures.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The seismic crisis that began in May, 2018 off the coast of Mayotte announced the onset of a volcanic eruption that started two months later 50 km southeast of the island. This seismicity has since ...been taken as an indicator of the volcanic and tectonic activity in the area. In response to this activity, a network of stations was deployed on Mayotte over the past three years. We used the machine learning-based method PhaseNet to re-analyze the seismicity recorded on land since March 2019. We detect 50,512 events compared to around 6508 manually picked events between March 2019 and March 2021. We locate them with NonLinLoc and a locally developed 1-D velocity model. While eruptions are often monitored through the analysis of Volcano-Tectonic (VT) seismicity (2–40 Hz), we focus on the lower frequency, Long Period (LP) earthquakes (0.5–5 Hz), which are thought to be more directly related to fluid movement at depth. In Mayotte, the VT events are spread between two clusters, whereas the LP events are all located in a single cluster in the bigger proximal VT cluster, at depths ranging from 25 to 40 km. Moreover, while the VT earthquakes of the proximal cluster occur continuously with no apparent pattern, LP events occur in swarms that last for tens of minutes. We show that during the swarms, LP events generally migrate downward at a speed of 5 m/s. While these events do not appear directly linked to upward fluid migration, their waveform signature could result from propagation through a fluid-rich medium. They occur at a different location than VT earthquakes, also suggesting a different origin which could be linked to the Very Long Period events (VLP) observed above the LP earthquakes in Mayotte.
A new submarine volcano has been discovered offshore Mayotte, a part of the Comoros volcanic archipelago located between Africa and Madagascar. The edifice arose from the sea-floor following a ...seismo-volcanic crisis that started in May 2018. This seismo-volcanic activity highlights very deep magma reservoirs and dykes in the East Mayotte volcanic system. Since the crisis, the region has experienced >2000 earthquakes with magnitude ≥3.5 and activity continues today (August 17, 2021). The earthquakes are unusually deep and distributed into two swarms: one 5–15 km east of Petite-Terre at 25–55 km depth and a second 25 km away at 30–50 km depth. Significant subsidence of Mayotte to the East has been assigned to the drainage of a deep magma chamber, inferred to be located 30 km from the coast. However, at present, the earthquake locations and geodetic observations have not been sufficient to image entirely the structure of the volcanic plumbing system. In this study, we construct Vp, Vs, dVp, dVs and Vp/Vs 3D velocity models to assess the deeper structure of the young volcano plumbing system, offshore and East of Mayotte. Using >3000 earthquakes from an ongoing monitoring effort, and a 1D velocity model determined onboard, we jointly inverted for velocity structures, earthquake locations, origin times, and station corrections using LOTOS software. The calculated 3D velocity models highlight a complex volcanic system down to 40 km depth. Specifically, we image 3 interpreted reservoirs, more or less consolidated/old. The main reservoir is located at about 30 km depth and deeper, making it one of the deepest magmatic chamber imaged. The reservoirs are connected by several old crystallized conduits, whose existence could have been influenced by the presence of an old fracture zone, globally oriented N130°, due to a regional strike-slip motion of the lithosphere. Moreover, gas-saturated rock may be present below the currently degassing Horse Shoe structure. We were unable to image connections between the new volcanic edifice and reservoirs or conduits due to a lack of resolution in that part of the study area.
•The first 3-D velocity models offshore Mayotte revealing 3 potential magma reservoirs more or less related to the ongoing eruption.•Reservoirs are connected by crystallized conduits with a spatial distribution constrained by regional lithosphere strike-slip faulting.•Low P and S velocities crust and mantle, suggesting for a widespread melt throughout the region.
Une fièvre mahoraise ou la leptospirose à Mayotte Bourée, Patrice; Durfort, Céline; Salmon, Dominique
Revue francophone des laboratoires,
July-August 2019, 2019-07-00, Letnik:
2019, Številka:
514
Journal Article
Recenzirano
La leptospirose, zoonose la plus fréquente dans le monde, a l’incidence la plus élevée des départements et régions d’outre-mer à Mayotte. Un Comorien de 32 ans immigré à Mayotte se présente pour ...fièvre et myalgies depuis huit jours. Les examens mettent en évidence une leptospirose, rapidement résolutive sous doxycycline. L’incidence en 2017 est de 66,3 cas pour 100 000 habitants, soit 170 cas déclarés. L’activité agricole et les co-expositions à la maladie (vie rurale, habitat dégradé, divers animaux et rats dans l’environnement, accumulation de déchets dans les rues) sont des facteurs majeurs de risque de contamination à Mayotte. Une amélioration de l’hygiène générale est indispensable pour diminuer l’incidence de cette infection.
Leptospirosis, the most common zoonosis in the world, has the highest incidence of overseas departments in Mayotte. A 32-year-old Comorian immigrated to Mayotte presents for fever and myalgia for 8 days. The examinations show a leptospirosis, quickly resolving under doxycycline. The incidence in 2017 is 66,3 cases per 100 000 inhabitants, 170 cases reported. Agricultural activity and co-exposure to the disease (rural life, degraded habitat, various animals and rats in the environment, accumulation of waste in the streets) are major risk factors for contamination on Mayotte. An improvement in general hygiene is essential to reduce the incidence of this infection.
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