Ebola: lessons from a 19th-Century London physician

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We are witnessing the largest Ebola epidemic in history.

Widespread transmission of the lethal viral disease has already led to well over 13,000 cases in West Africa. A handful of cases, primarily associated with travel from this region, have been reported in the US and Spain. While there are encouraging signs that the epidemic may finally be plateauing, two numbers underscore the need to maintain an aggressive international response. Ebola is killing 70% of those affected and according to some projections, West Africa might yet see as many as 10,000 new cases every week by the end of the year. To put these numbers in perspective, the next largest Ebola outbreak on record – in Uganda in 2000 lasted four months and totaled 425 cases.

With the global public health fraternity under fire for allowing the current crisis to spiral out of control, there have been calls to innovate: to apply newer (and often, more expensive) technology to Ebola control. However, the real answer may lie in massively scaling up the deployment of one of the oldest and most fundamental tools of preventive medicine a tool born out of an infamous outbreak of cholera in Victorian London and the pioneering efforts of Dr John Snow.

Lessons from the past

Cholera had been around in Britain since 1831. At the time, oral rehydration therapy was unknown and, for many of its victims, this diarrhoeal infection meant certain death in a matter of hours. In fact, while we now understand that a germ transmitted via contaminated water causes cholera, the prevalent theory of the mid-1800s held that it spread through “foul air. Against this backdrop, London’s Soho was the scene of what was then believed to be the worst outbreak of cholera in the UK – an outbreak that left 500 residents dead over the first 10 days of September 1854. Those 10 days, as we widely appreciate now, revolutionised the control of outbreaks and the practice of epidemiology – a branch of medicine with roots in the Hippocratic eraforever.

John Snow, a local physician, had treated patients with cholera during prior epidemics in London. Crucially, he had also tracked the distribution of the disease in different parts of the city. By 1849, decades before the cholera microbe was actually discovered, his logical observations had led him to deduce that the infection was waterborne and its spread somehow linked to the city’s water supply. However, his views on the subject continued to be dismissed as mere speculation by his own profession until 1854.

The Soho outbreak changed all that. Through a series of door-to-door visits interviewing contacts of cholera victims and by meticulously plotting cases on a map of the neighborhood, Snow was able to demonstrate that most victims in the ongoing outbreak lived close to and indeed consumed water from a pump on Broad Street. The local authorities, while largely focused on spraying the streets with chloride of lime (a costly preventive measure of the day now known to be ineffective), agreed on Snow’s insistence to also remove the handle of the Broad Street pump on September 8. With the pump put out of service, the source of infection was gone and the cholera outbreak ended soon after. This marked the beginning of what we now term “shoe-leather epidemiology” – a literal reference to the rigours of the fieldwork involved – and the birth of contact tracing.

Contact tracing

Contact tracing is already the cornerstone of the fight against Ebola, be it in Freetown or in New York. In the context of Ebola, contact tracing involves finding those who have been in close contact with a symptomatic case and monitoring them for 21 days for possible onset of the disease. What is needed is continued implementation of this strategy on a scale, and with intensity, as yet unprecedented in global health. Mathematical models forecasting the impact of potential interventions on the trajectory of the current epidemic show that a judicious combination of contact tracing, personal protection and safe burials delivered on a war footing across the countries worst-hit by the virus represents our best hope of eventually curbing Ebola transmission. The same models also suggest that a high-end experimental therapy such as ZMapp assuming it proved reasonably effective and one could get it to most patients hospitalised for Ebola would without a doubt save some lives, but would do little to check the propagation of the epidemic itself.

Is classic shoe-leather epidemiology deliverable on such a war footing? One of the few public health success stories of the current epidemic has been the containment of Ebola in Nigeria. The country has been declared Ebola-free after limiting the initial outbreak to 20 cases. At the heart of the Nigerian success have been 18,500 face-to-face visits health workers rapidly tracked down and painstakingly monitored nearly every contact of each suspected case of Ebola.

These experiences indicate that for every case of Ebola in West Africa at least 20 contacts will have to be followed, requiring a manifold increase in current contact tracing capacity. This presents a monumental challenge in health systems ravaged by war, poverty and the effects of geographical remoteness. The problem is compounded by international debates on quarantine policy and airport screening that, while important, threaten to hijack the public discourse on Ebola from its focus on the epicentre of the epidemic.

Dr Snow’s prescription was clear: outbreaks are best managed at their source. Ebola in West Africa must have the world’s sustained and undivided attention – and resources.

*Siddhartha Kar [2012] is doing a PhD in Public Health and Primary Care at the University of Cambridge with a focus on cancer genetics. He trained in medicine in India and in epidemiology in the US. Picture credit: Wiki Commons, Ethleen Lloyd and CDC.

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