A new method for the analysis of access period experiments, illustrated with whitefly-borne cassava mosaic begomovirus.

Reports of low transmission efficiency, of a cassava mosaic begomovirus (CMB) in Bemisia tabaci whitefly, diminished the perceived importance of whitefly in CMB epidemics. Studies indicating synergies between B. tabaci and CMB prompt a reconsideration of this assessment.

COVID-19 hospitalization rates rise exponentially with age, inversely proportional to thymic T-cell production.

Here, we report that COVID-19 hospitalization rates follow an exponential relationship with age, doubling for every 16 years of age or equivalently increasing by 4.5% per year of life ( = 0.98).

Estimating epidemiological parameters from experiments in vector access to host plants, the method of matching gradients.

Estimation of pathogenic life-history values, for instance the duration a pathogen is retained in an insect vector (i.e., retention period) is of particular importance for understanding plant disease epidemiology.

Different Plant Viruses Induce Changes in Feeding Behavior of Specialist and Generalist Aphids on Common Bean That Are Likely to Enhance Virus Transmission.

Bean common mosaic virus (BCMV), bean common mosaic necrosis virus (BCMNV), and cucumber mosaic virus (CMV) cause serious epidemics in common bean (), a vital food security crop in many low-to-medium income countries, particularly in Sub-Saharan Africa. Aphids transmit these viruses "non-persistently," i.e.

Cucumber mosaic virus 2b proteins inhibit virus-induced aphid resistance in tobacco.

Cucumber mosaic virus (CMV), which is vectored by aphids, has a tripartite RNA genome encoding five proteins. In tobacco (Nicotiana tabacum), a subgroup IA CMV strain, Fny-CMV, increases plant susceptibility to aphid infestation but a viral mutant unable to express the 2b protein (Fny-CMV∆2b) induces aphid resistance. We hypothesized that in tobacco, one or more of the four other Fny-CMV gene products (the 1a or 2a replication proteins, the movement protein, or the coat protein) are potential aphid resistance elicitors, whilst the 2b protein counteracts induction of aphid resistance.

Pathogenic modification of plants enhances long-distance dispersal of nonpersistently transmitted viruses to new hosts.

Aphids spread the majority of plant viruses through nonpersistent transmission (NPT), whereby virus particles attach transiently to these insects' probing mouthparts. Virus acquisition from infected plants and inoculation to healthy host plants is favored when aphids briefly probe plant epidermal cells. It is well established that NPT virus infection can alter plant-vector interactions, and, moreover, such pathogen modifications are found in a range of plant and animal systems.

Viral Manipulation of Plant Stress Responses and Host Interactions With Insects.

Do the alterations in plant defensive signaling and metabolism that occur in susceptible hosts following virus infection serve any purpose beyond directly aiding viruses to replicate and spread? Or indeed, are these modifications to host phenotype purely incidental consequences of virus infection? A growing body of data, in particular from studies of viruses vectored by whiteflies and aphids, indicates that viruses influence the efficiency of their own transmission by insect vectors and facilitate mutualistic relationships between viruses and their insect vectors. Furthermore, it appears that viruses may be able to increase the opportunity for transmission in the long term by providing reward to the host plants that they infect. This may be conditional, for example, by aiding host survival under conditions of drought or cold or, more surprisingly, by helping plants attract beneficial insects such as pollinators.

pH feedback and phenotypic diversity within bacterial functional groups of the human gut.

Microbial diversity in the human colon is very high with apparently large functional redundancy such that within each bacterial functional group there are many coexisting strains. Modelling this mathematically is problematic since strains within a functional group are often competing for the same limited number of resources and therefore competitive exclusion theory predicts a loss of diversity over time. Here we investigate, through computer simulation, a fluctuation dependent mechanism for the promotion of diversity.