No SARS-CoV-2 reinfection among staff health-care workers: Prospective hospital-wide screening during the first and second waves in Paris

International audienceObjectivesRisk of reinfection with SARS-CoV-2 among health-care workers (HCWs) is unknown. We assessed the incidence rate of SARS-CoV-2 reinfection in the real-life setting of a longitudinal observational cohort of HCWs from the Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, France, during the first and second waves of COVID-19 epidemic.MethodsFrom March to December 2020, HCWs were subjected to molecular and serology testing of SARS-CoV-2. Reinfection was defined as a positive test result during the first wave, either by serology or PCR, followed by a positive PCR during the second wave. Evolution of COVID-19 status of HWCs was assessed by a Sankey diagram.ResultsA total of 7765 tests (4579 PCR and 3186 serology) were carried out and 4168 HCWs had at least one test result during the follow-up period with a positivity rate of 15.9%. No case of reinfection during the second wave could be observed among 102 positive HCWs of the first wave, nor among 175 HCWs found positive by PCR during the second wave who were negative during the first wave.ConclusionsSARS-CoV-2 reinfection was not observed among HCWs, suggesting a protective immunity against reinfection that lasts at least 8 months post infection

Microbiogical data, but not procalcitonin improve the accuracy of the clinical pulmonary infection score

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Picoeukaryotes of the Micromonas genus: sentinels of a warming ocean

International audiencePhotosynthetic picoeukaryotes in the genus Micromonas show among the widest latitudinal distributions on Earth, experiencing large thermal gradients from poles to tropics. Micromonas comprises at least four different species often found in sympatry. While such ubiquity might suggest a wide thermal niche, the temperature response of the different strains is still unexplored, leaving many questions as for their ecological success over such diverse ecosystems. Using combined experiments and theory, we characterize the thermal response of eleven Micromonas strains belonging to four 1 species. We demonstrate that the variety of specific responses to temperature in the Micromonas genus makes this environmental factor an ideal marker to describe its global distribution and diversity. We then propose a diversity model for the genus Micromonas, which proves to be representative of the whole phytoplankton diversity. This prominent primary producer is therefore a sentinel organism of phytoplankton diversity at the global scale. We use the diversity within Micromonas to anticipate the potential impact of global warming on oceanic phytoplankton. We develop a dynamic, adaptive model and ran forecast simulations, exploring a range of adaptation time scales, to probe the likely responses to climate change. Results stress how biodiversity erosion depends on the ability of organisms to adapt rapidly to temperature increase

Impact de la température sur les interactions entre la microalgue marine Micromonas et les virus qui l’infectent

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High-resolution diatom/clay record in Lake Baikal from grey scale, and magnetic susceptibility over Holocene and Termination I

Tracing past climate signals from Lake Baikal sediments with a "multi-annual' resolution by conventional techniques is a difficult challenge since the sedimentation rates from Termination I up to the present range from 0.004 to 0.17 mm/year. In this paper, climate signals are reconstructed from three continuous sediment records from Vydrino Shoulder and Posolsky Bank in the Southern Basin, and Continent Ridge in the Northern Basin. For each coring site, a calendar age model was constructed using calibrated radiocarbon ages. The magnetic susceptibility is used to better constrain the age models over OIS4 to OIS1 The cores have been hardened using polymerized technique in order to allow the easy cut of thin sections that contain evidence for narrow biogenic/clayey laminations. The grey scale taken from the thin sections is used here as a high-resolution proxy record of diatom/clay ratio. The grey density values are qualitatively interpreted against the sediment components by optical microscopy from the thin sections. In the Northern Basin, the Continent station provides the best age model and sediment resolution over the Termination I period. In particular, four optima (i.e. Bolling, Allerod, Atlantic, and Subboreal) are indicated by substantial increases of the grey scale, whereas cold periods like the Younger Dryas correspond to lower grey scale values. We emphasize that the short-term variations in the grey scale at 20 mu m resolution could correspond to short climate responses in Lake Baikal sediments. (C) 2004 Elsevier B.V. All rights reserved.Continen