How the war on disease made our world

COVID-19 is, ironically, a function of the richer, more connected and more populous world created by the defeat of disease.

• Medical technology like artificial ventilators will keep the death rate from COVID-19 lower than in past pandemics like the 1918 flu.
• But the social distancing needed to slow its spread will exert a much worse economic toll than it would have a century ago because our much larger economy is far more dependent on global trade and uninterrupted human connection.
• "Globalization is both a vulnerability and a reason why our response to this, even with all the economic pain, will be much more effective than it was in the past," says Charles Kenny, a senior fellow at the Center for Global Development and the author of a forthcoming book on the history of disease.

Background: For most of humanity's history, disease and infection kept a check on human development. Population growth, economic growth, even the spread of people across the planet — all were curbed by the threat of contagion.

• As late as 1800, average global life expectancy was just 29 years. This wasn't because human beings couldn't live to an old age but because almost half of all people born died before their 50th birthday, mainly from contagion.
• Death from disease in urban areas was so rampant that up until the 19th century, cities were only able to maintain their population through a constant influx of migrants to replace the dead.

All that began to change in the 19th century, with the sanitary revolution and later the widespread development of vaccines and antibiotics.

• Untold numbers of lives were saved. Global life expectancy rose — to 71 years on average today — and with it, global population.
• Freed from the constant reaping of their citizens from infection, cities exploded, their larger populations becoming engines of rapid innovation. Global travel became safer and with it, the global trade that has helped drive startling levels of economic growth over the past century.
• "Our defeat of infection overcame the barriers to human development," says Kenny.

Yes, but: That defeat has been so total that we often take it for granted, especially in the developed world, where we are far more likely to die from heart attacks or strokes — conditions human beings rarely lived long enough to suffer from — than infectious disease. As a result, we've let our guard down.

• Global vaccination rates have stagnated and declined for diseases like measles in recent years, partially driven by anti-vaxxers who have no memory of a world threatened by childhood diseases.
• As antibiotic resistance grows because of overuse, we desperately need new drugs. Yet in January the World Health Organization warned the pipeline for new antibiotics was essentially dry.
• And of course the explosive spread of COVID-19 has shown just how unprepared the world was for a contagious, new infectious disease.

The bottom line: The reason COVID-19 feels so disruptive is because our world was built on the idea that events like this no longer happen. We won't get that world back until we beat this disease. And we can't safeguard that world unless we ensure it won't happen again.

Go deeper: The pandemic highlights the man-made disasters to come