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Urbanising cholera

April 15, 2011

Work in progress – by Rajib Dasgupta

Most accounts of the epidemiology of communicable diseases characterise the man (and on occasion the woman) of medicine and science as the single dominant hero – to borrow Dostoevsky’s expression, “a positively good man”.

The germ, on the other hand, is quite certainly the villain of the piece, to be cracked (in the laboratory) and controlled (through vaccines and antibiotics). Accounts of greater social sensitivity (by historians and anthropologists) deal with a wider range of social nuances that affect common women and men in myriad ways. Coming from a public health officer this is an insider-practitioner’s view that places common concerns centre stage. My work is constructing a social epidemiological account of cholera, taking a public-health perspective, with a focus on the urban poor. Detailed analyses of social determinants of a single disease are not common; indeed, the social determinants literature has largely developed in the context of non-communicable diseases in Western/industrialised societies.

Societal distributions and determinants of disease need to take into account political economy and political ecology; thus “power – both power over and power to do” is crucial for exposure to health hazards. While levels in real-life situations exist simultaneously (not sequentially), the proximal/distal framework may disjoin levels rather than connecting them. Examination of the problem of cholera as an urban health issue requires this sensitivity and therefore an adequate breadth of canvas.

This account brings to the fore the transformation of cholera from an ‘Old World’, highly fatal epidemic to a milder disease, an endemic entity (with a propensity for focal outbreaks) of contemporary megacities, clustered in locales where the urban poor reside. The social determinants of this acute communicable disease operate at multiple levels, mired in local economics and politics. Cholera is one of the classic diseases in the history of epidemiology.

John Snow’s seminal work on cholera epidemics in London (1820s–50s) marked a paradigm shift in epidemiological thinking for several reasons: a rational approach to the social determinants, inductive logic based on detailed and accurate descriptive data, and the right action for the right reasons (in contrast to sanitary physicians and miasmatic theories that were right in terms of action, for the wrong reasons). With subsequent shifts in analytical approaches, fuelled in part by epidemiological transition, a far more statistical approach has established itself as the gold standard of evidence- based medicine, focused on individual determinants (popularly, ‘risk factors’).

A slum area of Delhi

A slum area of Delhi, where cholera has been a major risk. Wellcome Images

My work takes an eco-social approach in examining the social determinants of cholera and deals with different aspects of the problem. It argues for a social epidemiological approach to develop a contextual understanding of diseases. Social determinants of health, a wide and complex field of enquiry, encompasses social class, caste, gender, ethnicity, education, infrastructure and access to public health services – to name a few. Social action needs to be based on a variety of evidence, including the historical. The emphasis is to identify the ‘causes of the causes’. That is what my work sets out to do for cholera in the context of a megacity (Delhi) where a large proportion of the population are ‘urban poor’, living and working in conditions of deprivation. The pandemics of cholera are traced in the context of northern India, including the Punjab and Delhi, demonstrating that the region was repeatedly affected by successive epidemics, largely on account of importation through trade routes. This has been traced to the current (seventh) pandemic with a detailed analysis of time trends including the threat of a potential eighth pandemic attributed to the emergence of a new strain (Vinbio cholerae O139) in 1993–94.

Detailed description of the process of planning for public health in Delhi links the city’s post-independence rapid growth and social inequities to access to water and sanitation services, therefore highlighting the emergence of cholera as an endemic urban health problem. The analysis of spatial distribution of cholera cases within Delhi illustrates the value of ‘area effects’ as an epidemiological approach. Detailed mapping and eco-social characteristics of colonies (vulnerable to cholera and other waterborne infections) mark a significant addition to existing knowledge.

A deconstruction of Delhi’s 1988 cholera epidemic, one of the most politically sensitive contemporary public health events, is an important contribution. The formal academic literature available focuses exclusively on microbiological aspects, while NGO literature does cover some of the social determinants. The uniqueness of this analysis is in the additional access to and analyses of official documents and collation of a wide range of information – into a cogent story demonstrating that social inequities adversely affected populations condemned by legal biases of urban planning and infrastructure.

A primary inquiry has been analysed to foreground the social determinants. An in-depth study of 300 households (100 each from three infrastructurally disadvantaged settlements) examined the role of behavioural factors. It is generally agreed that pathways of transmission of waterborne diseases are complexly intertwined. It is increasingly being argued by powerful players of international health that interventions based on ‘secondary routes’ (i.e. behavioural determinants including storage and hygienic issues) are effective in significantly reducing transmission of diarrhoeal diseases. Based on statistical analysis of household-level incidence data and behavioural determinants, I conclude that behavioural issues lose their significance when pitted against stronger infrastructural determinants, access to which is a function largely of planned provision.

The Report of the WHO Commission on Social Determinants of Health is a concerted public health effort towards evolving a “new global agenda”. A remarkable and bold initiative, it has been received with both optimism and scepticism. The Commission cannot be faulted for not recognising that the momentum and nature of contemporary urbanisation is detrimental to the health and wellbeing in particular of the urban poor. It calls for urgent improvement of living conditions in slums and considers that most countries wish to be self- sufficient in resources. Upfront, it sees a clear role for local governments in housing and basic services, and as a prerequisite to that political recognition of illegal settlements and regularisation of tenureship. It is hoped that a work of this nature will strengthen the new agenda.

Dr Rajib Dasgupta is Fulbright Senior Research Fellow and Visiting Associate Professor at Johns Hopkins Bloomberg School of Public Health, USA.


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