Volume 361:741-743		August 20, 2009		Number 8

This transition is happening chaotically, resulting in a disorganized urban landscape. Although many expect urbanization to mean an improved quality of life, this rising tide does not lift all boats, and many poor people are rapidly being absorbed into urban slums. Urbanization, in fact, is a health hazard for certain vulnerable populations, and this demographic shift threatens to create a humanitarian disaster. The threat comes both in the form of rising rates of endemic disease and a greater potential for epidemics and even pandemics. To protect global health, governments and international agencies need to make commensurate shifts in planning and programs, basing all changes on solid epidemiologic and operational research.

Although natural disasters and armed conflicts cause migration into urban centers, most people relocate to cities in search of employment. When they arrive, many find only one affordable housing option: illegal and unplanned dense settlements lacking basic public infrastructure, where they must live in lodgings made from tenuous materials, such as used plastic sheets, discarded scrap metal, and mud. The United Nations Human Settlements Program (UN-Habitat) reports that 43% of urban residents in developing countries such as Kenya, Brazil, and India and 78% of those in the least-developed countries such as Bangladesh, Haiti, and Ethiopia live in such slums.² These slums, which are making up an increasing proportion of growing cities, lack not only most basic government services but also political recognition; as a result, so do their inhabitants. These residents are usually tolerated and their presence tacitly accepted, but the local government generally ignores them, accepting no responsibility for accounting for them in planning or the provision of services.

The current public health paradigm delineates urban health hazards as comprising injuries, pollution, and chronic diseases, such as diabetes and hypertension. Although these hazards are indeed more specific to urban than to rural areas, urbanization also exacerbates long-standing hazards specific to populations that have not undergone the epidemiologic transition from a predominance of infectious diseases. Increasing the population density in cities without proper water supplies and sanitation increases the risk of transmission of communicable diseases. Mortality among children under 5 years of age and among infants is higher in urban slums than in rural settings (see table).³

View this table: [in this window] [in a new window]   Childhood Death Rates in Japan versus Rural and Urban Regions of Kenya.

 
Though in most countries health care is more limited in rural than in urban areas, the urban environment may lack health support often provided in rural settings while also posing new risks. For example, for women and children, the rural environment provides a community of kinship that often ensures physical safety, food security, and the availability of child care. Without these safeguards, many women’s mobility is limited in urban areas. Mobility and child care assistance from more experienced women allow mothers to perform two of the three steps that are theoretically fundamental to health care utilization: identifying illness and seeking care (the third being delivering care). Differential rates of death reflect this effect of urbanization, but we require more data in order to assess the true extent of this problem and other urban health risks. Currently, collected data are rarely disaggregated down to the level of individual city neighborhoods, and slum populations are generally not included when health statistics are reported.

Improved systems for collecting data in slums are urgently needed for the planning of infrastructure construction, programs, and resource allocation. Precise data that distinguish among types of residence, locations, and socioeconomic strata would reveal the varied effects of urbanization on health indicators, allowing for focused interventions.

View larger version (88K): [in this window] [in a new window]   A Doctor Examining a Child in a Slum in Chandigarh, India, 2008. From Pradeep Twari/Photoshare

 
We believe that the world’s wealthier countries need to invest in capturing these data and improving public health systems. Doing so is not purely altruistic; it serves the self-interest of all countries, because poor urban areas can easily become a breeding ground for emerging infections and potential pandemics. The outbreak of severe acute respiratory syndrome (SARS) in Hong Kong in 2002 and 2003, which was believed to have originated in rural China, demonstrated how dense urban living could ignite a global health crisis. In a slum, the lack of surveillance and adequate health care might well result in more rapid spread of undetected diseases; without the necessary resources, it is difficult to implement any kind of preventive, containment, or treatment measures. Developed countries also have a financial stake in the requisite surveillance and health care systems: even conservative estimates of the cost of SARS to the economies of Europe and North America run to billions of dollars.

View larger version (36K): [in this window] [in a new window]   Shantytown in Monrovia, Liberia, 2007. From UN-Habitat

 
Understanding health-related behavior and the logistics of the health care environment of urban areas can also aid in the design of appropriate interventions. All three factors necessary to the effective utilization of health care — illness identification, care seeking, and care delivery — vary within urban settings. Although slum residents often live close to many health care providers, they generally have little access to high-quality care. Care-seeking patterns show that although less expensive, higher-quality government clinics are often available, slum residents who do seek care tend to choose more expensive private providers — for a multitude of reasons, from perceived quality to ease of access.⁴ Studies show that the care received by the urban poor is often of low quality. One study examining the care provided by 100 private practitioners in an urban slum in Mumbai, India, found 80 different treatment regimens being used for tuberculosis, only 4 of which met the guidelines of the World Health Organization.⁵

In some cases, new interventions are required for this population, but in others, interventions that are known to be effective simply need to be translated into effective programs. Fundamental public health services, such as vaccination, a safe water supply and sanitation, and oral rehydration therapy, remain important, and operational research is required in order to implement them effectively. Adapting interventions for implementation by community health workers or trained midwives has shown benefit, and we believe that a cadre of health care workers practicing in slums must be trained in order to reach this population.

Our knowledge base also needs to be supplemented through dedicated research. Epidemiologists must develop methods for collecting precise and accurate data and surveillance on the health of urban populations. Research must be conducted on the design of interventions and approaches to using proven public health tools that exploit the advantages conferred by urban settings, such as the concentration of target populations and better communication and transportation infrastructures for delivery of care and health education. And governments, nongovernmental organizations, and private providers must commit themselves to implementing new policies and programs. Many projects and field research efforts fall by the wayside when no governing or implementing agency “scales up” initial results. Governments need to determine the structure of health care provision, administration, and regulation, and nongovernmental organizations should aid in promoting good governance, increasing capacity, and ensuring access to care.

As the world becomes increasingly urban, the health of the urban poor may suffer. Decades of progress in public health could be erased, and the stage could be set for devastating pandemics of infectious disease. Action is needed now to avert such a disaster.

No potential conflict of interest relevant to this article was reported.

Source Information

From the Harvard Affiliated Emergency Medicine Residency based at Brigham and Women’s Hospital and Massachusetts General Hospital (R.B.P.), and the Division of Global Health and Human Rights, Department of Emergency Medicine, and the Department of Pediatrics, Massachusetts General Hospital, and Harvard Medical School (T.F.B.) — all in Boston.

References

1. State of the world population 2007: unleashing the potential of urban growth. New York: United Nations Population Fund, 2007. 
   
2. United Nations Human Settlements Programme. The challenge of slums: global report on human settlements 2003. London: Earthscan, 2003.
   
3. Population and health dynamics in Nairobi’s informal settlements. Nairobi: African Population and Health Research Center, 2002.
   
4. Kapil U, Bharel SM, Sood AK. Utilisation of health care services by mothers in an urban slum community of Delhi. Indian J Public Health 1989;33:79-79. [Medline]
   
5. Garner P, Thaver I. Urban slums and primary health care. BMJ 1993;306:667-668. [Free Full Text]