COVID-19 spread predicted using weather forecasting technique

Scientific methods normally used to forecast weather have been borrowed to predict how rapidly COVID-19 could spread in different countries as lockdown is eased, as well as assess the effectiveness of measures put in place.

Meteorologists from the University of Reading and National Centre for Earth Observations were part of an international team that applied data assimilation, a technique that combines multiple sources of information to estimate how a situation will develop over time, to the pandemic. It suggests it is possible to make reasonably accurate predictions of how easing measures might affect the spread of the virus up to two weeks in advance.

This technique is usually used to pair computer simulations with real weather observations to forecast future weather. Previous computer model forecasts can be tested against the subsequent weather data to help make future short-term predictions more accurate.

When applied to the coronavirus, observations including hospital admissions, the number of patients in intensive care, and the number of daily deaths can be combined with models calculating risk of vulnerability, exposure, infection and death.

Dr. Javier Amezcua, one of three Reading scientists that worked on the study, said: "Most data is uncertain to some degree, but combining as much of it as possible from different sources can iron out some of this uncertainty when predicting future events. Meteorologists use this method all the time to understand and forecast natural processes like weather, but its uses extend beyond that.

"We decided to apply this technique we routinely use to the most uncertain situation facing the world right now—COVID-19. Although we are not experts on viruses, our findings demonstrate the potential of measures that reduce the amount of contact people have with one another to save many lives."

Professor Alberto Carrassi, coordinator of the team at Reading, said: "This has been a genuine interdisciplinary exercise that demonstrates how methods and approaches rooted in one discipline can be applied beyond their original terrain of applications, creating opportunities for further cross-fertilisations."

The research, submitted to the journal Foundations of Data Science, allows estimations to be made of how situations will develop in different scenarios, and can be used to create longer-term forecasts. This means it could be useful to predict the impact changes of lockdown policies, such as reopening schools and shops or increasing permitted socialising, might have on the spread of infections.

The team applied the technique to estimate coronavirus spread in eight different countries around the world—England, France, Netherlands, Norway, US, Canada, Brazil and Argentina—which have all seen the virus spread in different ways.

In England, the now-familiar R number—the number of people a person with COVID-19 is likely to infect—was effectively reduced below 1 by the government's lockdown measures. It was altered by the team to create three possible scenarios: where it reduced to 0.5, increased to 1 or increased further to 1.2.

Although uncertain, the approximate number of deaths projected by 1 September in each scenario were 57,000 (R=0.5), 63,600 (R=1) and 76,400 (R=1.2). The number of deaths in England as of 1 June was approximately 45,000.

Dr. Alison Fowler, the third Reading researcher who worked on the study, said: "Understanding the uncertainty of the model and measurements is crucial to the success of data assimilation. This was particularly challenging to quantify when dealing with reported deaths due to COVID-19, hospitalisations and number of positive cases, in which the collection of data is complicated by so many political and social issues."

Professor Geir Evensen, from the NORCE: Norwegian Research Centre, who led the study, said: "A key result from this work is that we can estimate accurately how the reproductive number varies in time in response to implementing or loosing up various mitigation measures."

Professor Parveen Yaqoob, Pro-Vice Chancellor (Research & Innovation) at the University of Reading, said: "Reading is known worldwide for excellence in environmental and health research, but we really excel by working together across disciplines. I am proud that this group is using their expertise and applying it to help tackle the coronavirus crisis, as are many of others across the University."