COVID-19 Scenario Analysis Tool

MRC Centre for Global Infectious Disease Analysis, Imperial College London

Note: Simulation outputs should not be interpreted as predictions

Frequently Asked Questions

What is an unmitigated scenario?

This is a scenario in which no interventions are introduced and hence the infection rapidly spreads throughout the country. This is very unlikely to happen in practice as both governments and their populations will respond in a way that reduces contacts and hence onward transmission. It is however useful to understand the value of putting in place interventions in terms of reducing morbidity and mortality.

What data are you using for my country?

To enable the software to be as up to date as possible, we input daily updates of the number of deaths from COVID-19 in each country as compiled by the European Centre for Disease Control. The model is calibrated to this number.

Local demography is used for each country based on the UN World Population Projections. Contact patterns are based on representative data for the setting but are not country-specific due to limited data.

Other epidemiological parameters in the model are based on our best current understanding of the virus and will be updated regularly – please see the Research page.

The timing of major interventions is currently taken from the Oxford Government Response Tracker. We are working to incorporate Google movement data as a more nuanced way to estimate the impact of interventions up to the current time.

Is transmission between countries captured?

No, the model assumes homogeneous transmission within each country. This is clearly an approximation, especially for large countries, and it is likely that transmission will occur across international borders.

Why can I not change the model parameters?

The underlying model parameters are detailed in the “Research” tab. These are our current best estimates based on extensive and ongoing epidemiological analyses of SARS-Cov-2 virus transmission. Varying individual parameters can lead to combinations that no longer correctly represent transmission. Researchers who are familiar with modelling should consider the equivalent R package “squire” which is available here.

Why does my country have a fixed start date for interventions that I can’t change?

In order to calibrate the model to the epidemic state in each country, we use statistical fitting methods to incorporate the first reported major social distancing intervention (partial or national movement restrictions). If such interventions have been put in place, this is shown in the start date. This information is obtained from a global database. It is possible that this date may not be completely accurate for all countries and we will endeavour to improve this information going forwards.

Why can’t I model specific interventions such as school closure or face masks?

In this current version we are only modelling an average transmission reduction. We plan to incorporate specific interventions in future versions.

My country says there are no interventions but we have these in place.

We are currently using a global database that collates information on the interventions that are in place. The information in the database may not be complete for all countries.

We currently only model partial or national movement restrictions; therefore other interventions may not appear in the interface. We are working to better incorporate all interventions and their impact.