Période d'incubation

Résumé

On appelle période d’incubation le délai entre la contamination et l’apparition des premiers symptômes d'une maladie. Exemples Du fait des variations inter-individus, les périodes d'incubations sont toujours sous la forme d'intervalles. Lorsque c'est possible, il est mieux de l'exprimer par la moyenne entre les et centiles, mais cette information n'est pas toujours disponible. Dans beaucoup de cas, les périodes d'incubation sont plus longues chez l'adulte que chez l'enfant ou le nourrisson. Notes et références Catégorie:Maladie infectieuse he:המודל הפסיכוסקסואלי#שלב החביון

Source officielle

https://fr.wikipedia.org/wiki/P%C3%A9riode_d'incubation

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Relevant pandemic-spread scenario simulations provide guiding principles for containment and mitigation policy developments. In this report we discuss model predictions for infected, recovered and dead people during a pandemic. The model consists of a simple reaction mechanism, which considers the population size, reported and unreported infections, reported and unreported recoveries and number of deaths. It is assumed that recovered persons are immune (e.g. mutations are not considered), that the virus can only be passed on by unreported infected persons and that no vaccine will be found within the considered periods. Moreover, the model does not take into account age dependency, but considers higher mortality rates due to temporary shortage of emergency rooms. Some of the model parameters have been fitted to the reported cases outside of China1 from January 22 to March 12 of the 2020 Covid-19 pandemic. The other parameters were chosen in a plausible range and sensitivity studies were performed; among all tested parameter values, those leading to the lowest number of deaths were chosen for the presented case studies, i.e., the predictions are rather optimistic. Scenarios in which the infection rate per person is reduced for periods of 680 and 183 days (”social distancing phase”) and scenarios in which the testing frequency is increased for 680 days (”frequent testing phase”) are studied. While the predicted number of deaths can dramatically be reduced during the ”social distancing” and ”frequent testing” phases, the fatality numbers increase again some time after these phases end; for all these scenarios the predicted final number of deaths lies between 3% and 5% of the initial population (not much different from the base case). It is interesting, however, that more frequent testing seems to be much more effective than social distancing and may cause less economic damage. The currently low detection rate is obviously linked to the long incubation period typical for Covid-19. Incubation for typical flu is much shorter, and as soon people fall ill and stay at home, they are effectively detected and do not further spread the virus.

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Structural Order of the Molecular Adlayer Impacts the Stability of Nanoparticle-on-Mirror Plasmonic Cavities

Aqeel Ahmed, Karla Banjac, Fernando Pablo Cometto, Christophe Marcel Georges Galland, Magalí Alejandra Lingenfelder, Sachin Suresh Verlekar

Immense field enhancement and nanoscale confinement of light are possible within nanoparticle-on-mirror (NPoM) plasmonic resonators, which enable novel optically activated physical and chemical phenomena and render these nanocavities greatly sensitive to minute structural changes, down to the atomic scale. Although a few of these structural parameters, primarily linked to the nanoparticle and the mirror morphology, have been identified, the impact of molecular assembly and organization of the spacer layer between them has often been left uncharacterized. Here, we experimentally investigate how the complex and reconfigurable nature of a thiol-based self-assembled monolayer (SAM) adsorbed on the mirror surface impacts the optical properties of the NPoMs. We fabricate NPoMs with distinct molecular organizations by controlling the incubation time of the mirror in the thiol solution. Afterward, we investigate the structural changes that occur under laser irradiation by tracking the bonding dipole plasmon mode, while also monitoring Stokes and anti-Stokes Raman scattering from the molecules as a probe of their integrity. First, we find an effective decrease in the SAM height as the laser power increases, compatible with an irreversible change of molecule orientation caused by heating. Second, we observe that the nanocavities prepared with a densely packed and more ordered monolayer of molecules are more prone to changes in their resonance compared to samples with sparser and more disordered SAMs. Our measurements indicate that molecular orientation and packing on the mirror surface play a key role in determining the stability of NPoM structures and hence highlight the under-recognized significance of SAM characterization in the development of NPoM-based applications.

AMER CHEMICAL SOC2021

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Malachite Green Interferes with Postantibiotic Recovery of Mycobacteria

Neeraj Dhar, Ekaterina Gelman, John McKinney

The genus Mycobacterium comprises slow-growing species with generation times ranging from hours to weeks. The protracted incubation time before colonies appear on solid culture medium can result in overgrowth by faster-growing microorganisms. To prevent contamination, the solid media used in laboratories and clinics for cultivation of mycobacteria contain the arylmethane compound malachite green, which has broad-spectrum antimicrobial activity. Malachite green has no impact on the plating efficiency of mycobacteria when cells are grown under normal conditions. However, we found that malachite green interfered with colony formation when bacteria were preexposed to antibiotics targeting cell wall biogenesis (isoniazid, ethionamide, ethambutol). This inhibitory effect of malachite green was not observed when bacteria were preexposed to antibiotics targeting cellular processes other than cell wall biogenesis (rifampin, moxifloxacin, streptomycin). Sputum specimens from tuberculosis patients are routinely evaluated on solid culture medium containing high concentrations of malachite green. This practice could lead to underestimation of bacterial loads and overestimation of chemotherapeutic efficacy.

2012

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Structural Order of the Molecular Adlayer Impacts the Stability of Nanoparticle-on-Mirror Plasmonic Cavities

Aqeel Ahmed, Karla Banjac, Fernando Pablo Cometto, Christophe Marcel Georges Galland, Magalí Alejandra Lingenfelder, Sachin Suresh Verlekar

AMER CHEMICAL SOC2021