Assessing the potential impact of transmission during prolonged viral shedding on the effect of lockdown relaxation on COVID-19.

A key parameter in epidemiological modeling which characterizes the spread of an infectious disease is the generation time, or more generally the distribution of infectiousness as a function of time since infection. There is increasing evidence supporting a prolonged viral shedding window for COVID-19, but the transmissibility in this phase is unclear. Based on this, we develop a generalized Susceptible-Exposed-Infected-Resistant (SEIR) model including an additional compartment of chronically infected individuals who can stay infectious for a longer duration than the reported generation time, but with infectivity reduced to varying degrees. Using the incidence and fatality data from different countries, we first show that such an assumption also yields a plausible model in explaining the data observed prior to the easing of the lockdown measures (relaxation). We then test the predictive power of this model for different durations and levels of prolonged infectiousness using the incidence data after the introduction of relaxation in Switzerland, and compare it with a model without the chronically infected population to represent the models conventionally used. We show that in case of a gradual easing on the lockdown measures, the predictions of the model including the chronically infected population vary considerably from those obtained under a model in which prolonged infectiousness is not taken into account. Although the existence of a chronically infected population still remains largely hypothetical, we believe that our results provide tentative evidence to consider a chronically infected population as an alternative modeling approach to better interpret the transmission dynamics of COVID-19

Careers of self-initiated expatriates: exploring the impact of context

Guest editoria

Unsupervised machine learning predicts future sexual behaviour and sexually transmitted infections among HIV-positive men who have sex with men

Machine learning is increasingly introduced into medical fields, yet there is limited evidence for its benefit over more commonly used statistical methods in epidemiological studies. We introduce an unsupervised machine learning framework for longitudinal features and evaluate it using sexual behaviour data from the last 20 years from over 3'700 participants in the Swiss HIV Cohort Study (SHCS). We use hierarchical clustering to find subgroups of men who have sex with men in the SHCS with similar sexual behaviour up to May 2017, and apply regression to test whether these clusters enhance predictions of sexual behaviour or sexually transmitted diseases (STIs) after May 2017 beyond what can be predicted with conventional parameters. We find that behavioural clusters enhance model performance according to likelihood ratio test, Akaike information criterion and area under the receiver operator characteristic curve for all outcomes studied, and according to Bayesian information criterion for five out of ten outcomes, with particularly good performance for predicting future sexual behaviour and recurrent STIs. We thus assess a methodology that can be used as an alternative means for creating exposure categories from longitudinal data in epidemiological models, and can contribute to the understanding of time-varying risk factors

Unsupervised machine learning predicts future sexual behaviour and sexually transmitted infections among HIV-positive men who have sex with men.

Machine learning is increasingly introduced into medical fields, yet there is limited evidence for its benefit over more commonly used statistical methods in epidemiological studies. We introduce an unsupervised machine learning framework for longitudinal features and evaluate it using sexual behaviour data from the last 20 years from over 3'700 participants in the Swiss HIV Cohort Study (SHCS). We use hierarchical clustering to find subgroups of men who have sex with men in the SHCS with similar sexual behaviour up to May 2017, and apply regression to test whether these clusters enhance predictions of sexual behaviour or sexually transmitted diseases (STIs) after May 2017 beyond what can be predicted with conventional parameters. We find that behavioural clusters enhance model performance according to likelihood ratio test, Akaike information criterion and area under the receiver operator characteristic curve for all outcomes studied, and according to Bayesian information criterion for five out of ten outcomes, with particularly good performance for predicting future sexual behaviour and recurrent STIs. We thus assess a methodology that can be used as an alternative means for creating exposure categories from longitudinal data in epidemiological models, and can contribute to the understanding of time-varying risk factors

One-pot isothermal DNA amplification Hybridisation and detection by a disc-based method

[EN] An integrated sensor comprising isothermal DNA amplification and in situ detection is presented. The method principle is based on recombinase polymerase amplification (RPA) and detection in the microarray format by compact disc technology as a high-throughput sensing platform. Primers were immobilised on the polycarbonate surface of digital versatile discs (DVD) and, after hemi-nested amplification, multiplexing identification of each tethered product was achieved by optical scanning with a 650 nm-laser of the DVD drive. The efficiency of one-pot hybridisation/elongation/detection depended strongly on probedensity and other factors such as the concentration of the unbound primers present in solution. The optimised conditions provided equivalent amplification factors (7.3 x 10(8) -8.9 x 10(8) fold) to those obtained by conventional reactions performed in vials. The proposed method was applied to Salmonella detection (generic by hns and oriC genes, and specific for subspecies I by STM4507 gene). A triplex assay was satisfactorily compared to the non-integrated protocols. Food and vaccine samples were analysed in a shorter time with less handling. The results indicate that the multiplex DVD assay is a simple, competitive, isothermal, portable system that is particularly useful for microbiological routine analysis. (C) 2014 Elsevier B.V. All rights reserved.This research has been funded through Projects GVA-PROMETEO/2010/008 (Generalitat Valenciana) and CTQ/2013/ 45875-R (MINECO). The Spanish Ministry of Education and Science provided S.S.F. with a grant for her PhD studies.Santiago Felipe, S.; Tortajada-Genaro, LA.; Morais, S.; Puchades, R.; Maquieira Catala, Á. (2014). One-pot isothermal DNA amplification Hybridisation and detection by a disc-based method. Sensors and Actuators B: Chemical. 204:273-281. https://doi.org/10.1016/j.snb.2014.07.073S27328120

Situational factors shape moral judgements in the trolley dilemma in Eastern, Southern and Western countries in a culturally diverse sample

The study of moral judgements often centres on moral dilemmas in which options consistent with deontological perspectives (that is, emphasizing rules, individual rights and duties) are in conflict with options consistent with utilitarian judgements (that is, following the greater good based on consequences). Greene et al. (2009) showed that psychological and situational factors (for example, the intent of the agent or the presence of physical contact between the agent and the victim) can play an important role in moral dilemma judgements (for example, the trolley problem). Our knowledge is limited concerning both the universality of these effects outside the United States and the impact of culture on the situational and psychological factors affecting moral judgements. Thus, we empirically tested the universality of the effects of intent and personal force on moral dilemma judgements by replicating the experiments of Greene et al. in 45 countries from all inhabited continents. We found that personal force and its interaction with intention exert influence on moral judgements in the US and Western cultural clusters, replicating and expanding the original findings. Moreover, the personal force effect was present in all cultural clusters, suggesting it is culturally universal. The evidence for the cultural universality of the interaction effect was inconclusive in the Eastern and Southern cultural clusters (depending on exclusion criteria). We found no strong association between collectivism/individualism and moral dilemma judgements

Antimicrobial Activity and Cytotoxicity of Ag(I) and Au(I) Pillarplexes

The biological activity of four pillarplex compounds featuring different metals and anions was investigated. The toxicity of the compounds against four bacterial strains [Bacillus subtilis (ATCC6633), Staphylococcus aureus (ATCC6538), Escherichia coli (UVI isolate), Pseudomonas aeruginosa], one fungus (Candida albicans), and a human cell line (HepG2) was determined. Additionally, a UV-Vis titration study of the pillarplexes was carried out to check for stability depending on pH- and chloride concentration changes and evaluate the applicability in physiological media. All compounds are bioactive: the silver compounds showed higher activity against bacteria and fungi, and the corresponding gold pillarplexes were less toxic against human cells