The numbers game: using maths to combat coronavirus

Tue, 21 Apr 2020 16:21:00 BST

Mathematicians from the University are using their computer modelling expertise to advise the government on how to best protect the UK population during the coronavirus emergency. To better predict the future, they are looking back to historic pandemics like the bubonic plague for clues on infection patterns.

The group are using mathematical modelling so that they can advise the UK’s Scientific Pandemic Influenza Group on Modelling (SPI-M) who report to the Scientific Advisory Group for Emergencies (SAGE) to provide scientific and technical advice to support COBRA, the UK government’s national crisis team led by the Prime Minister.

“SAGE relies on fast, accurate external science advice from its expert groups, such as SPI-M, that we at Manchester and other universities are members of. This stops the government from guessing, helping them make decisions that will impact millions of people based on facts and evidence,” explains Dr Ian Hall, a member of this specialist task force, who has worked for Public Health England and retains an honorary position with the agency.

The group is made up of Dr Hall, Dr Thomas House and Dr Lorenzo Pellis, who are all from the University’s Department of Mathematics. This core trio is supported by a group of dedicated PhD and research assistants who are busy helping with the daily number crunching. They include Jacob Curran-Sebastian, Martyn Fyles, Elizabeth Fearon, Christopher Overton, Hugo Lewkowicz, Rajenki Das, Luke Webb, Bindu Vekaria, Xiaoxi Pang and Helena Stage.

The Manchester statisticians have been data mapping from the earliest days of this growing crisis. They specialise in risk to communities that are in enclosed places, such as prisons or large vessels like a cruise ship, the highly social communities found in schools, and much smaller social environments like our family homes.

Manchester advice has so far helped decision-makers to:

  • risk-assess the impact of quarantine on dozens of UK passengers from the Diamond Princess which was docked at Yokohama, Japan, after becoming a coronavirus hotspot
  • order mass school closures sooner rather than later – and not wait for the Easter break
  • consider the role of household transmission and the most effective advice to the public around staying in isolation.

“We’ve been in a coronavirus bubble since the start of the year,” says Dr Hall. “We get new data every day from Public Health England, and the more we get, the better we can build a more accurate picture for certain community groups in the UK.”

In January and February, the Manchester team were providing advice to help planners prepare the nation for the coming COVID-19 pandemic. However, throughout February the situation escalated in Europe, with data quickly indicating the picture was also changing for the UK.

Dr Pellis, for example, was looking at growth rates across Europe. He put a paper to the UK government which, based on the data from Italy, Spain, and other European states, recommended that the UK implement a policy of closure as soon as practical. A few days later, coupled with other evidence, universal school closures were ordered, marking the beginning of a historic implementation of restrictive measures across the nation.

Dr Hall admits that COVID-19 has been a challenge to predict. For example, it can affect people in different ways. For some it can be particularly serious, making that person very ill and suffer a high fever. “When you’re in that condition you don’t want to socially engage but to stay in bed instead – so although highly contagious, that person actually comes into contact with very few people,” he explains.

Other people with the virus are only mildly affected, and despite being less contagious, they go out and unwittingly act as spreaders of the disease.

To map these complex trends, the Manchester team have looked at other virus-based pandemics which occurred in 1880, 1918–19, 1957, 1968, and the most recent, the 2009 swine flu outbreak, which many in the health sector expected would be the ‘big one’. But the 2009 incident was less devastating than expected because the elderly population of that time had been exposed in their youth to similar flu outbreaks in the 1950s and 1960s, and thus developed ‘herd immunity’. COVID-19 is a completely new disease, which no-one in the world has natural immunity to.

COVID-19 is so novel that the team have looked even further back in history to previous bacteria-based pandemics, including the bubonic plague. Although the origins of this devastating disease are from fleas living on infected rats, the plague also has a pneumonic form which can cause a severe lung infection, which can then be passed on through person-to-person infection.

The most famous and most devastating recorded outbreak is the Black Death, peaking in Europe from 1347 to 1351. More useful to modern analysts is the outbreak of the plague that took place in Cairo in 1801, for which epidemiological data is uniquely available thanks to French army medical officers accompanying the Napoleonic expedition into Egypt at that particular time.

The combination of modelling based on empirical data is augmented with Dr Hall and his team applying assumptions based on more qualitative information, their own experience of working in healthcare and related sectors, and a growing understanding of the epidemiology of previous global pandemics. This combined knowledge is helping the Manchester group create realistic models that are relevant to the current crisis.

“The situation is fast changing,” admits Dr Hall, “but the UK government has now taken the necessary steps, however drastic, to help mitigate the spread of coronavirus to the wider population. I expect our work will focus more on enclosed social environments as millions of people stay confined in their family homes – even this is a new phenomenon at such a large scale.”

Dr Hall is keenly observing China as it begins to relax its own suppression measures, believing the worst is now over for them in severely affected areas, such as the city-region of Wuhan which has been in lockdown for two months.

“Time will tell – but one thing that I would say for certain is that the people in the UK need to take government advice very seriously, especially regards mixing between young and more elderly and frail population groups," he continues. "If, as a society, we can all collectively adopt the new social distancing protocols, then the sooner we can all expect to get out of this unprecedented situation.”