How epidemics change us

As governments around the world try to contain the pandemic of Covid-19, they often draw on experiences of past epidemics.

The swift and (so far) successful response of Hong Kong and Singapore, despite their proximity to the origin of pandemic in Hubei, China, has been attributed to the living memory of the 2003 epidemic of SARS. SARS left behavioural change and infection control practices that are now proving useful against Covid-19.

In the UK, where none of the coronavirus and influenza-virus epidemics of the previous decades had significant impact, the controversial and now abandoned strategy of protecting the most vulnerable population while letting the virus percolate through the remainder of the population in order to build herd immunity drew on data collected during the catastrophic influenza of 1918-1920. The idea is that immunity developed during the first encounter with the virus was meant to protect against the even more deadly “second wave”. Building herd immunity in this ‘natural’ way comes with a huge death toll, which British policymakers initially believed acceptable (coming clearly from eugenicist, utilitarian and neoliberal positions).

But while past pandemics can provide valuable guidance for strategies to combat new pathogens, their impact goes much further. Past pandemics have changed our demography, society, technology, and society; they have changed the environment and the climate.

So in what way could Covid-19 change us?

The emergence of Covid-19 is not an unusual or unexpected event. New human pathogens have evolved continuously through human history though historically low population densities and lack of communication between populations used to limit their spread. Plague had been endemic around the Caspian Sea before it travelled down the trade routes through Central Asia, first towards China (in the 1330s) and then westwards, reaching Southern Italy in 1347. But were it not for the strong population growth and development of the cities in 13th century Europe, the epidemic might not have taken hold and almost certainly it would not have become the Black Death that is likely to have killed at least half Europe’s population and one third of the Middle East’s.

Several centuries later, cholera, endemic to India, travelled through trade and military routes established by the British Empire; the 1918-1920 influenza was so tightly linked to the First World War that the effects of each are difficult to disentangle.

Pathogens have changed us biologically. Through human evolution, diseases have been the strongest selective forces. Populations have been decimated upon first encounters with pathogens as the histories of indigenous Pacific populations show following the arrival of Europeans together with influenza, measles and tuberculosis, to name a few.

Our genome bears marks of historical encounters with diseases. Forms of chronic anaemia among the populations of Mediterranean and African descent result from a trade-off between resisting severe malaria (by producing a malformed haemoglobin resistant to the parasite) and having sufficient amount of normal haemoglobin to supply the body with oxygen. A mutation in the gene involved in immune response relatively common in Europe, appears to provide resistance to the infection with HIV. Many carriers of this gene coding come from a single ancestor in Northern Europe; while AIDS is a novel disease (i.e. it hadn’t been seen before), this mutation, it seems, protected from deadly epidemics of the Middle Ages such as smallpox or perhaps plague.

But beyond direct impacts on demography and genome, pandemics had dramatic and far-reaching impact on human societies. Post-Black Death, the dramatic population decrease forced rulers to see people as the most valuable resources of the state. The lack of workforce stimulated technological innovation, but also hastened the fall of the feudal system. In particular, cities that suffered under the epidemic began to understand the health of the population as a responsibility and developed the earliest forms of public health.

The first anti-epidemic measures were ad hoc but in 1377, Dubrovnik on the Croatian Adriatic Coast – a city perched between East and West, forced to continue trade to survive – introduced quarantine as an innovative and institutional measure that simultaneously secured economic activity and population health.

Later, in the 19th century, while waves of cholera were spread by population movement caused by political unrest, revolution and migration, restrictive measures used to control the disease caused further upheaval. Quarantine and forced hospitalisation were perceived as unfair attacks on the oppressed masses, the population from the lower socioeconomic strata who were most affected.

So what is the likely impact of Covid-19?

While the impact of the certain and profound economic crisis is difficult to predict, it seems probable that the pandemic will strengthen already existing trends. An obvious one is the transition to online work and further dissolution of the traditional workplace: a process already under way but now sharply accelerating. The pandemic has brought air travel to a complete halt: with pre-existing worries over its contribution to climate change and the rapid development of tools for online meetings, it might never resume pre-2020 levels.

Many see the drop in greenhouse gases as a temporary phenomenon and likely to bounce back quickly, as was the case post- global financial crisis. Yet there may be political opposition to allow that to happen, especially as the way globalised economies operate is put in question, with complex supply chains crossing continents proving to lack resilience. In terms of geopolitics, while at the onset of the crisis with Wuhan at epicentre, China seemed to be in a vulnerable position, its handling of the epidemic and then positioning as the source of knowledge and supplies to combat the pandemic globally may help its claim to the leading global superpower.

Finally, biologically, Covid-19 seems to affect older population much more severely. With mortality rates lower than past pandemics, it may not have the same evolutionary effect as plague or smallpox. But stringent hygienic practices, isolation, reduction in air pollution and even diminished popularity and public reach of the “anti-vaxx” movement are likely to result in changing patterns of disease in the coming years, decades and possibly intergenerationally.

As history is showing, these impacts are likely to be more complex and far-reaching than we can envisage today.