Originally published on March 12, 2020 on CEBM.net
Carl Heneghan and David Howard
Global Centre on HealthCare and Urbanisation
Kellogg College, University of Oxford
Respiratory infections transmit through the air, through surfaces and by close contact. The recent coronavirus outbreak, COVID-19, is primarily spread by respiratory droplets when an infected person coughs or sneezes. Viruses within the droplets can enter through the eyes, nose or mouth to infect other individuals. Close contact – less than 1.5 meters – with the larger COVID-19 droplets increases the chance of infection. The virus also appears to spread by direct contact and by contact with contaminated surfaces and objects.
As a hub for migration and travel, cities can spread infections. Tuberculosis, for instance, is much higher in big cities: in New York City, the incidence is four times the national average; in the Democratic Republic of the Congo, 80% of those with TB live in cities.
Several recent global infections are thought to be caused by viruses previously only found in animals, including Middle Eastern Respiratory Syndrome (MERS), Sudden Acute Respiratory Syndrome (SARS), HIV, bird flu (avian flu), swine flu and COVID-19. Based on genome sequencing of patients with COVID-19 bats are the likely source of the infection; an unknown intermediate animal likely acted to transmit the virus from bats to humans.
The COVID-19 and SARS outbreaks are thought to have started in Chinese wet markets. In these markets live and dead animals are in close contact with people, and animals are often slaughtered in front of customers, creating a breeding ground for disease. The first person to die from COVID-19 was a regular shopper at the Huanan wet market in Wuhan where wild animals, including birds, rabbits, bats, snakes, pigs and pangolins are sold, many illegally.
The Wuhan market was closed on January 1st, 2020, and last month China announced a permanent ban on the selling and transport of wild animals to and from markets. The wildlife-farming industry is valued at $74 billion and employs over a million people in China. The growing awareness that diseases such as coronavirus can jump from animals to humans will require changes in how food is sourced and sold in tightly knit communities.
An increasing proportion of the world’s population are becoming city dwellers, likely to reach 70% by 2050 – that is 2.5bn more people living in urban areas than today. The physical built environment is critical to successful and sustainable urban dwelling; access to safe drinking water, sanitation and drainage are vital – 673 million people have no access to sanitation. Half a million diarrhoeal deaths were estimated to be caused by inadequate drinking water, and 280,000 deaths due to insufficient sanitation in 2012. Effective urban design and efficient urban infrastructure are the founding blocks for healthy cities. Urban green spaces, public parks or fora, have been intuitive components of urban development for millennia.
High population densities present the ideal conditions for spreading disease. Poor public health infrastructure can exacerbate problems, promoting the spread of infection. While the built environment provides numerous opportunities for transmitting infections as people go around their daily lives, the spatial concentration of humans can allow for more effective and quicker provision of health treatment or prevention policies, as opposed to across dispersed communities.
In 1854, Dr John Snow’s discovery that cholera could be conveyed by water, and his locating of the contaminated water pump source in the London parish of Soho, helped to stall an epidemic that had already killed 600 residents. This link between medical knowledge and effective urban infrastructure and design remains just as central for today’s and tomorrow’s cities. Connecting such knowledge and best practices in this sphere is increasingly important on the global scale. The World Health Organisation’s Healthy Cities Network connects practitioners, researchers and policymakers to promote and share new innovations and information on urban health. Archive Global is an international non-profit organisation dedicated to engaging architectural design to combat disease, ‘using one basic right – housing – to deliver one basic need – health’. Poverty, and poorly-serviced or inadequately-constructed urban settlements are a pressing focus for support, to prevent widespread infections, and where the taken-for-granted ability to wash hands with soap and clean water in the minority, wealthy world, is often a gaping need.
Cities can exacerbate disease transmission as people move around, interact with the environment and come into contact with infected surfaces. Some coronaviruses can remain infectious on materials for up to nine days. While using standard bleach or ethanol preparations can disinfect the surface within minutes, we need a rethink of the materials used in communal spaces. Engineers will be called on to develop surfaces that reduce the risks of infection transmission. The US Centers for Disease Control and Prevention, for example, is currently evaluating the survival of coronavirus on different surfaces: on copper and steel, it’s about 2 hours, while on cardboard and plastic it’s much longer.
Garbage collection, often taken for granted in high-income countries is associated with high levels of diarrheal diseases, intestinal parasites, and water-borne diseases. Reliable sanitation infrastructure is vital to the prevention of several contagious diseases; infrastructure that is often lacking in centres undergoing rapid urbanization.
Airborne infections are also affected by ventilation and air flows indoors. Yet, air quality is often ignored; however, ventilation can reduce the transmission of disease, and natural ventilation can be an effective environmental measure to reduce the risk of spread of infections in health care facilities. The notion of the ‘urban gym’, using green infrastructure and considerate design to encourage inclusive walkability, physical exercise or engagement with the natural environment is another avenue to healthier cities, building physical and mental well-being into the urban fabric. Cleaner, integrated transport systems and ‘contactless’ design reduce vulnerabilities to illness, while protecting the health vulnerable.
The role of a city and its environment can support or damage health. Positive urban design should act to improve living conditions, with good access to health and social services. Sub-standard urban ecosystem can spread infections; good urban design can reduce the risk of infections.