Megacities will struggle to cope with sudden infectious disease outbreaks unless they embrace sustainable growth and the urban poor, as metropolitan populations are set to surge.
This population explosion is a major concern for urban planners and epidemiologists, in light of changing landscapes in cities and expectations that they will draw another 2.5 billion people by 2050. Such growth would drive the number of city dwellers from 55 per cent of the global population to more than two-thirds, with 90 per cent of urban growth expected in Asia and Africa.
Such trends lead to big questions, say the authors of a paper in Urban Studies. “The massive increase of the global urban population over the past few decades has been concentrated primarily in ex-urban areas, which has posed new challenges to the control of infectious disease,” they say. Ex-urban areas are classified as areas with lower-density residential populations than suburbs and can be found further beyond city limits.
“Rural-to-urban migrants tend to land on the edges of cities, where there isn’t necessarily as much infrastructure and governance regimes to make those areas less at risk to infectious disease outbreaks,” says lead author Creighton Connolly, a senior lecturer in development studies and the global South at the University of Lincoln.
Connolly and colleagues from Canada’s York University argue that “new ecological niches” are emerging for disease spread, pointing to urban encroachment into wildlife habitats increasing exposure to zoonoses — diseases that jump from animals to humans.
During West Africa’s Ebola outbreak in 2014, the World Health Organization notes, the disease spilled over into cities after almost 40 years of outbreaks in central Africa that were largely confined to remote rural areas.
Connolly’s team point out that 12 million people already live in the Democratic Republic of Congo’s capital Kinshasa — triple the joint population of cities affected by the 2014 outbreak. The DRC recently declared the end to its tenth Ebola outbreak in the east of the country, as a genetically unrelated strain of the disease emerged in the northwest.
Eric Fèvre, professor of veterinary infectious diseases at the University of Liverpool and jointly appointed at the International Livestock Research Institute in Nairobi, Kenya, says food systems supplying urban areas are an interface “bringing elements of the farm deep into the city”.
“Clearly, thinking about how we design our built environments will make a difference to the scale of risks,” he says.
Crowding versus density
However, Sameh Wahba, global director of the urban, disaster risk management, resilience and land global practice for the World Bank, emphasises that city growth in itself is not the problem.
“The issue is not density per se, but rather the way the density is managed — [that is] when it becomes poorly managed and density becomes crowdedness, with substandard housing and poor infrastructure,” he says.
Even in poorer cities with limited governance capacity, Wahba says, a “liveable density” is possible. It just means that city leaders and governments need to carefully plan ahead for anticipated urban growth — with retrospective interventions in crowded slums potentially costing four to seven times more.
In fact, he says, density needs to increase through higher buildings in certain areas with one- or two-storey shacks, as cities will be unmanageable if they continue peripheral expansion.
For disease management, crowdedness can mean disaster.
Open-access mapping tools are helping to reveal disease risk hotspots.
Wahba points to a World Bank-developed methodology that combines data from high-resolution satellite imagery with population and mapping datasets from WorldPop, Facebook and OpenStreetMap.
During Covid-19, Wahba and colleagues have used this methodology to map Mumbai, Kinshasa and Cairo, which indicated the location of high-risk hotspots due to overcrowding, or overloaded public facilities because of a lack of domestic water and sanitation facilities.
More than 80 per cent of the population in Kinshasa was found to be at heightened risk of disease and up to 25 per cent in Mumbai and Cairo — with the method suggesting areas in need of short-term emergency attention and longer-term slum upgrades for future disease resilience.
Saleemul Huq, director of the International Centre for Climate Change and Development (ICCCAD) in Dhaka, Bangladesh, says existing emergency systems in cities in developing countries can be repurposed to also manage epidemics.
Meanwhile, ICCCAD has been pushing a scheme pinpointing 20 smaller towns that could permanently resettle up to one million people each, to spread the expected sizeable burden of people displaced by flooding over the next two decades.
But, says Huq, one of the biggest problems is that people living in burgeoning slums and informal settlements are regularly omitted from decisions — partly because their identity is frequently unknown — and their vulnerability will only increase without effective schemes to include them in city and national strategies as populations swell.
“The urban [poor] have been forgotten — they leave their villages, they come to the city, they live in a slum, and then that’s it,” he says.
“I think the [Covid-19] crisis has just shown us how big this issue was. It’s been under the radar for a long time … It’s bursting out and making itself visible.”
Sheela Patel is founder and director of the India-based Society for the Promotion of Area Resource Centers (SPARC), which supports the urban poor in developing countries. She believes urban communities need to be involved from the outset in programmes aimed at improving city facilities or solving problems with technology. She thinks these have all-too-often been top-down, non-scalable and fail to reach the people they are intended for.
“You need local initiatives that can be the agents of support and assistance,” says Patel, which do not come from the “magic wand” of announcing a new technology or cure-all strategy.
Meanwhile, a whole host of data on urban conditions has been collected by slum dwellers via the Know Your City initiative of organisation Slum Dwellers International, which Patel chairs.
But globally, she fears things returning to “business as usual” once a vaccine is found for Covid-19, even though she says the pathways are there to address the issues faced by the urban poor and cities in general. “There is no shortage of resources in the world to make that happen,” she says.
Cities provide many health and other public service benefits precisely because of people’s proximity, but the Covid-19 crisis has highlighted the need for more connected, resilient cities.
Sustainable urban growth is possible if cities are fully inclusive, says Aniruddha Dasgupta, global director of the Ross Center for Sustainable Cities at the World Resources Institute.
Data can make vulnerable people visible and encourage decision-makers to allocate resources, he says.
“I really hope that what we are witnessing right now actually does open people’s eyes about what crises will look like in the future,” he says.
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