Mathematical modelling of the dynamics and containment of COVID-19 in Ukraine.

COVID-19 disease caused by the novel SARS-CoV-2 coronavirus has already brought unprecedented challenges for public health and resulted in huge numbers of cases and deaths worldwide. In the absence of effective vaccine, different countries have employed various other types of non-pharmaceutical interventions to contain the spread of this disease, including quarantines and lockdowns, tracking, tracing and isolation of infected individuals, and social distancing measures. Effectiveness of these and other measures of disease containment and prevention to a large degree depends on good understanding of disease dynamics, and robust mathematical models play an important role in forecasting its future dynamics. In this paper we focus on Ukraine, one of Europe's largest countries, and develop a mathematical model of COVID-19 dynamics, using latest data on parameters characterising clinical features of disease. For improved accuracy, our model includes age-stratified disease parameters, as well as age- and location-specific contact matrices to represent contacts. We show that the model is able to provide an accurate short-term forecast for the numbers and age distribution of cases and deaths. We also simulated different lockdown scenarios, and the results suggest that reducing work contacts is more efficient at reducing the disease burden than reducing school contacts, or implementing shielding for people over 60.

A new comparison of marine dispersion model performances for Fukushima Dai-ichi releases in the frame of IAEA MODARIA program.

A detailed intercomparison of marine dispersion models applied to the releases from Fukushima Dai-ichi nuclear power plant was carried out in the frame of MODARIA program, of the IAEA. Models were compared in such a way that the reasons of the discrepancies between them can be assessed (i.e., if they are due to the hydrodynamic part, the dispersion part, and the ultimate reasons). A sequential chain of dispersion exercises was carried out with this purpose. The overall idea is to harmonize models, making them run with the same forcing in a step-by-step procedure, in such a way that the main agent in producing discrepancy between models can be found. It was found that the main reason of discrepancies between models is due to the description of the hydrodynamics. However, once this has been suppressed, some variability between model outputs remains due to intrinsic differences between models (as numerical schemes). The numerical experiments were carried out for a perfectly conservative radionuclide and for (137)Cs (including water/sediment interactions). Model outputs for this radionuclide were also compared with measurements in water and sediments.