COVID-19 seeding time and doubling time model:an early epidemic risk assessment tool

Background:As COVID-19 makes its way around the globe,each nation must decide when and how to respond.Yet many knowledge gaps persist,and many countries lack the capacity to develop complex models to assess risk and response.This paper aimed to meet this need by developing a model that uses case reporting data as input and provides a four-tiered risk assessment output.Methods:We used publicly available,country/territory level case reporting data to determine median seeding number,mean seeding time(ST),and several measures of mean doubling time(DT)for COVID-19.We then structured our model as a coordinate plane with ST on the x-axis,DT on the y-axis,and mean ST and mean DT dividing the plane into four quadrants,each assigned a risk level.Sensitivity analysis was performed and countries/territories early in their outbreaks were assessed for risk.Results:Our main finding was that among 45 countries/territories evaluated,87%were at high risk for their outbreaks entering a rapid growth phase epidemic.We furthermore found that the model was sensitive to changes in DT,and that these changes were consistent with what is officially known of cases reported and control strategies implemented in those countries.Conclusions:Our main finding is that the ST/DT Model can be used to produce meaningful assessments of the risk of escalation in country/territory-level COVID-19 epidemics using only case reporting data.Our model can help support timely,decisive action at the national level as leaders and other decision makers face of the serious public health threat that is COVID-19.

Delayed seed dispersal species and related traits in the desert of the United Arab Emirates

The ability of plants to safely retain seeds in the mother plant is an adaptive mechanism described in many desert plants.However,research about delayed seed dispersal species in the desert of the United Arab Emirates(UAE)is lacking.This study aims to identify these delayed seed dispersal species and assess the relationships of the presence of delayed seed dispersal with plant growth form,habit,spatial dispersal,antitelechoric mechanism,and seed release time.The relationships between the presence of delayed seed dispersal and the above studied traits were assessed by using the Pearson Chi-square test and Nonlinear Principal Components Analysis(NLPCA).Results showed that a total of 46 delayed seed dispersal species were recorded(15.0%of 307 studied species)and the highest incidence occurred in the Fabaceae family(17.4%).Delayed seed dispersal species were predominantly perennial plants(73.9%)with spatial restricted dispersal(67.4%),which released seed in the dry season(45.7%).The dominant groups of delayed seed dispersal species were persistent fruits species and synaptospermy(28.3%).All graminoids showed persistent lignified fruits,while prostrate annuals were basicarpic species with myxospermy.Sandy habitats had the highest number of delayed seed dispersal species(54.3%),whereas salt flats had the lowest(23.9%).In the desert of the UAE,delayed seed dispersal species spread seeds until the end of the dry and windy season,thus breaking seed dormancy at this time and ensuring seed germination in the next arrival of the rainy season.This morphological and ecological adaptation of delayed dispersal species is essential to the survival and sustainable development of vegetation in desert environments.