Assesing COVID-19 Transmission By Prediction Modelling
Action plans to combat the current SARS-CoV-2 pandemic have been put in place all over the world in an attempt to lessen COVID-19 transmission. The reproduction number has been found to respond to changing public healthinterventions during pandemic waves. However, due to severe under-ascertainment of cases, the actual global burden of SARS-CoV-2 remains unknown. The use of reported deaths has been suggested as a more reliable source of information, as it is less likely to be under-reported. The daily deaths from previous infections are weighted by their probability of death; using statistics on deaths reported; one can deduce the actual number of conditions while accounting for their age demographics.
Anastasia Chatzilena of the University of Bristol, Nikolaos Demiris of the Athens University of Economics and Business, and Konstantinos Kalogeropoulos of the London School of Economics and Political Scienceworked together to model the transmission rate using daily reported deaths from Greece, Portugal, the United Kingdom, Germany, Sweden, and Norway. To assess COVID-19 transmission, researchers used a Bayesian framework and integrated estimates of the total number of daily cases with data on daily laboratory-confirmed cases to determine the daily reporting ratio.
3D Animation: SARS-CoV-2 virus transmission leading to COVID-19
Modelling Framework
Compared to laboratory-confirmed instances, the researchers relied only on the reported number of fatalities as a more credible source of information. Researchers built a modelling framework that connected daily new infections to reported mortality using publicly accessible data sources, producing illnesses via a stochastic transmission model. The analysis spans the months of March 2020 to September 2021. The researchers looked for any differences between data given by national health authorities and data stored in the COVID-19 Data Repository, and they picked the most integrated dataset for each country.
After the first COVID-19 case was identified in early March 2020, Greece and Portugal implemented many control measures to avoid large-scale epidemics. Before their statewide lockdowns, both nations' earlier efforts, such as cancelling significant public events and closing schools, helped reduce the virus transmission rate (Rt). On estimate, Rt for Greece was much below throughout Portugal's time, which had brief variations of Rt high above. Between August and September, after the restriction measures were lifted, COVID-19 transmission re-emerged in both nations. Rt was estimated to have fallen before the enforcement of lockdowns, which temporarily raised Rt.
After Christmas and New Year's loosened controls and the creation of new transmissible variations, a steady increase in Rt is expected in Greece in early 2021; because of this, control efforts were tightened up until June, resulting in decreased transmission levels. Although an emergency was issued in early November, the transmission was not easily contained. We anticipate that Rt will reach its most significant level since the first wave by the end of December 2020. During Portugal's third wave, the highly transmissible alpha form drove hospitals to capacity. Rt. As regulatory restrictions were relaxed in summer 2021, both nations saw considerable increases in Rt.
Transmission Model
Several epidemiological models have been presented to predict the dynamics of COVID-19 transmission and the influence of preventive actions on these dynamics. Non-pharmaceutical interventions, such as social distancing recommendations, limits on the size of indoor and outdoor gatherings, promotion of teleworking, self-isolation of symptomatic individuals, school closures, and ultimately stay-at-home measures, aim to reduce contact rates between individuals while also affecting the relative infectiousness of infected individuals.
These control techniques have evolved through time; different action plans have been implemented based on each country's epidemiological circumstances, and local people have responded differently to these actions between pandemic waves. Based on these factors, it appears that a flexible model should be used to capture the dynamics of the effective transmission rate. The researchers utilized a stochastic extension of the well-known deterministic SEIR compartmental model, which posits a homogeneously mixing population with all individuals equally vulnerable and infectious if infected.
Conclusion
The researchers modelled the transmission rate as a diffusion process with discrete volatility phases for each pandemic wave, revealing the influence of control techniques and changes in individual behaviour. They analysed the situation of six European nations and estimated the time-varying reproduction number and the actual cumulative number of infected people. They provided a more accurate estimate of COVID-19 transmission since they calculated the exact number of infections via fatalities. They also estimated the daily reporting ratio and explored how variations in mobility and testing affected the inferred amounts.
