“I work in the Milner Centre for Evolution, specialising in infectious diseases that spread between animals and humans – so-called zoonotic diseases. Covid-19 is caused by a virus called SARS-CoV2 which likely evolved in bats. Bats are associated with many other viruses, including rabies and Ebola. They have extraordinary immune systems that can repair damage in their DNA and they also live a very long time relative to their body size. This means they go through life picking up all sorts of diseases and end up as a little bag of viruses that don’t affect them but can be passed on to other species.

“It’s possible that humans have been in contact with bats for a long time. Some societies would have lived in caves so it may be that some diseases evolved during primeval times to spread between bats and humans because we were living in proximity. Making the jump from animals to humans is a difficult thing for a virus to do, because every mammal has specific immune defences. It usually takes a virus a while to adapt to a new host before it can start to transmit, but Covid-19 seemed to have developed its own skeleton key.

“One theory behind this is the pressure on ecosystems around the world. Not only are humans encountering exotic animals more than ever before, different species are also coming into contact with one another. Different bats are hibernating together in caves at a higher density, and it may be that this has put pressure on viruses to jump from one bat species to another, so they’re getting better adapting to new hosts.

Once a virus can get from one bat species to another, it’s a smaller jump to infect another mammal, such as humans.

“There are three major forms of disease transmission – one is ingesting dirty water or contaminated food, the second is via an intermediate vector such as a mosquito that can pass on malaria, and the third major route is respiratory, which is what we think we’re seeing with this virus. It’s believed that droplets of moisture are released by simply exhaling and virus particles can travel up to two metres before falling to the ground and dying.

“We haven’t seen this strain of coronavirus before and neither have our immune systems. It’s like when Columbus went to the New World and brought with him measles and TB and whole societies were decimated. Before the outbreak, all eyes were on flu, which would have been simpler in terms of producing a vaccine and therapeutic drugs. The coronavirus family of viruses is completely different so we’re starting from scratch.

“Looking forward, this pandemic can be seen as part of a pattern of an increasingly frequent ‘spillover’ of pathogens from animals to humans over recent decades. Hopefully we will emerge from this crisis with a clearer perspective on the public health risks resulting from increasing pressure on natural ecosystems, as well as those from intensive farming.”

“As a mathematical biologist my job is to take biological systems and to represent them either as a series of equations or in lines of computer code. Once we have these models of the real systems, we can start to ask questions that are either infeasible or unethical to investigate in real life. This way, we can make predictions about how the systems will evolve as time goes on. I’ve worked on everything, from understanding the way locusts swarm and how to stop them, to predicting the complex development of an embryo, to modelling how diseases spread.

“For some time now, mathematical epidemiologists have been unpicking the mysteries of infectious disease. They have been suggesting preventative measures to halt the spread of HIV, bringing the Ebola crisis to heel, highlighting the risks to which the growing anti-vaccination movement is exposing us and fighting global pandemics. We’ve been building our expertise for over a century now. Indeed, models are now informing how we respond to Covid-19.

“One of the simplest mathematical models of disease spread splits the population into three categories: everyone who is capable of being infected (‘susceptibles’), those who have contracted the disease (‘infectives’) and those who have recovered and are now immune, or have died (‘removed’). This is the S-I-R model and it has been used to understand dengue fever in Latin America, swine fever in the Netherlands and norovirus in Belgium, providing vital lessons for how to prevent diseases spreading.

Whether an outbreak spreads or dies out is largely dictated by the basic reproduction number, or R0.

If a disease has an R0 less than 1, then the infection will die out quickly as each infectious person passes on the disease, on average, to less than one other individual. This means the outbreak cannot sustain its own spread. If R0 is larger than 1 then the outbreak will grow exponentially. R0 can typically be broken down into the size of the population, the rate of infection, and the rate of recovery or death from the disease. Increasing the first two of these factors increases R0, while increasing the recovery rate reduces it, as there is less time to pass the disease to others.

“Then there’s the effective reproduction number, often just called R. This is the average number of secondary infections caused by an infectious individual at a given point in the outbreak’s progression. If, by intervention, the effective reproduction number can be brought below one, then the disease will die out. This is what mathematicians are doing when they model the impact of an intervention. They suggest ways in which that intervention will alter one or more of these factors and by how much. They then build that into their calculation of R and see what impact it has.

“I hope that by explaining the ideas and the concepts clearly we can encourage more people to appreciate that ours is not only a living and breathing subject, but also one of vital importance."

“It’s said that the virus doesn’t discriminate, but Covid-19 is playing out in a world that is deeply unequal in many ways. Governments and policymakers need to be aware of how the virus could exacerbate these inequalities in the future to minimise that impact.

“Lockdown has seen a huge increase in reports of gender-based violence, with many women having to share homes with abusers. Refuge, one of the UK’s largest domestic abuse charities, reported a 120% increase in calls to their helpline in early April. There are also reports that domestic femicide in this country has doubled compared with stats from the last five years, and we’ve seen these figures replicated across Europe and around the world. Some governments have been responding to this – France made about 20,000 hotel rooms available for victims, for example – but this needs to continue to be a top priority.

“Healthcare is another concern. Emergencies like this obviously make it more difficult for people to access regular health services. This can have a specific impact on women when it comes to areas such as maternal and sexual reproductive healthcare, as governments may be tempted to reallocate resources from these areas to frontline services. This can also be seen as a window of opportunity for some policymakers in areas where reproductive rights are already heavily politicised, and we’ve seen attempts at restrictions made across a number of settings in the course of the pandemic, from Texas to Poland.

“Also on the subject of healthcare, women make up 70% of the global health workforce. At the time of writing, the UK has seen a disproportionate number of female and BAME workers dying. Then there are the issues around protective equipment. Aside from the nationwide shortages, PPE is designed for male bodies, meaning it’s often too large for the female-dominated workforce, making it uncomfortable at best and ineffective at worst.

“Not only has there been a profound impact on people’s lives, but also their livelihoods. Unprecedented measures have been taken to stabilise economies, including guaranteeing salaries. However, at a global level around 70% of women’s employment is in the informal sector, meaning that women are more likely to miss out on these government-backed schemes. And when recessions result in cuts to government spending, we know that women are more likely to be impacted. An appreciation of the gendered impact of any financial downturn should be key to policymakers.

“But the government briefings are a stark reminder of how unrepresentative the UK is in terms of politics, civil service, scientific and academic fields. In light of this, it’s difficult to hope that the response to Covid-19 is going to be inclusive when the decision-making so far has been the reserve of a racial and gendered elite. The pandemic is at risk of exacerbating gender inequalities in our world and we need to be aware of that as we hopefully move beyond it.”

“The history of modern government is a history of its relationship with plagues and pandemics. They’ve resulted in a profound transformation in the organisation of power – even the very idea of the modern state was born in response to the Black Death.

“We’ve also seen how responses to infectious diseases have compounded some of the worst aspects of society. For instance, blame for the Black Death was very much pinned on Jewish travellers and traders – it was the birth of anti-Semitism in Europe. Fast-forward to today and we’re seeing racist sentiment towards Chinese people. We know the politicisation of pandemics can lead to racialised politics and we must be alert to that danger.

“We’ve also seen a negative fall back into predictable war metaphors. It’s no coincidence that leaders play to this because they know it improves their popularity. It also means you can easily discredit any form of dissent. This idea that we’re all in this together and the virus is indiscriminate is not true – we know that certain vulnerable groups are far more susceptible, especially when it comes to poverty and class as we’ve seen in the United States.

It’s hard to have a war with an invisible enemy; we knew that with the War on Terror. A war requires enemies and when the virus is embodied, people start looking for scapegoats. This language of war gives rise to a certain order of politics that normalises militarism and leads to a creeping authoritarianism.

“After the Black Death we also saw the emergence of policing – not in response to crime but the need to regulate and survey populations. We’ve seen the introduction of temporary policing measures during this outbreak and we must be mindful that this doesn’t become something that re-orders the policing of societies in ways which can be normalised very quickly, and are very difficult to reverse after that.

“This will be a pivotal moment in history and I’d like to think it will lead to better global cooperation and understanding, because one thing this virus shows is that borders mean nothing. I recently interviewed the Humanitarian Director for Save The Children, Gareth Owen, who said this feels like a case of humanitarianism coming home. We’re recognising everyday insecurities – notably food and health – things which many people around the world are affected by daily. Hopefully things won’t ‘go back to normal’ and we will have a better ethical appreciation of people who live with these vulnerabilities every day. We should have gone through this process transformed.”