Few residents of the world’s great metropolises would have thought much about plagues before this year. Outside China and east Asia – made vigilant by swine flu and Sars – the trauma of pandemics such as Spanish flu or typhoid has largely faded from popular memory. But our cities remember.

An outbreak of yellow fever in Philadelphia in 1793 prompted administrators to take over the task of cleaning streets, clearing gutters and collecting rubbish. It worked, and governments across the US adopted the responsibility over the next decades. A misconception that the odour emanating from wastewater was responsible for diseases such as cholera prompted one of the world’s first modern underground sewer systems in London, and the development of wider, straighter and paved roads - which helped prevent water from stagnating.

Cities have evolved over the centuries according to theories of how to fight disease, turning features such as public parks and sewers into “a mundane part of city thinking”, says Michele Acuto, a professor of global urban politics at the University of Melbourne.

The legacy Covid-19 might leave on the world’s great cities is being hotly debated, although most specialists admit it is too early to know for sure. “It will depend in the end on how we analyse this virus: how is it spreading? How is it making people sick?” says Roger Keil, a professor of environmental studies at Toronto’s York University. “We don’t know the full answers, but once they become clearer, urban planners and other professionals will start to think as their predecessors did 100 years ago, as they laid sewer pipes and cleaned out parts of the city that were considered insalubrious.”