Cholera: Not a disease of the past

In a world of rapid economic and technological progress, an expanding health care sector and rapidly evolving innovations, diseases that “western” societies are about to forget, represent a dangerous reality for all those living in resource poor settings around the globe. Cholera is undoubtedly one of those.

What is it?

Cholera is an acute enteric infection of the small intestine, caused by the ingestion of the bacterium Vibrio cholerae, present in faecally contaminated water or food [1]. In its most severe form, it is characterised by a sudden onset of acute, watery diarrhoea, which if left untreated, can lead to quick dehydration and death. Although high hygiene standards and optimal water quality have lowered cholera´s incidence to “near extinction” levels in most of the developed world, it remains a major and severe public health challenge for many developing regions across the globe, primarily those lacking appropriate infrastructures and functioning sanitation systems [2]. In fact, in 2015, 42 countries reported nearly 180.000 new infections, including 1.304 deaths [3].

The burden

Understanding the actual scope of a problem is vital for effective mitigation. However, cholera´s real burden remains largely unknown and is predominantly driven by incomplete reporting and inadequate surveillance and monitoring. Estimations tend to range between 1.3 to 4 million annual infections and between 21.000 and 134.000 cholera-attributable deaths globally [4]. Furthermore, it has been suggested that ~60% of V. cholerae infections are fully asymptomatic [5], while about 80% of symptomatic cases are non-severe, often mild enough to avoid hospitalisation and reporting [6].

Although the actual burden is difficult to assess, Africa undoubtedly remains one the world´s most disproportionally affected regions. Throughout the 47 years since the seventh cholera pandemic reached the continent in 1970, the disease has become endemic in many East, Central and West African countries [7], with the risk of epidemics being largest during rainy seasons. The largest recent outbreak in West and Central Africa was declared in June 2014 and claimed over 2,000 lives with over 90.000 reported cases, mainly in Ghana, Nigeria, Niger and the Democratic Republic of the Congo [3]. A considerable proportion of the West and Central African population lacks access to clean water, while a much larger number lacks access to adequate sanitation and basic toilet facilities, disproportionally affecting the poorest of the poor.

The Cholera “highway”

Cholera spreads along West Africa’s waterways, coastal regions, rivers and lakes, where busy, income-generating fishing activities and trade routes run. Experts refer to coasts and major waterways (e.g. the Niger River) as cholera´s “highway”, with water and fish allowing for a “high speed” expansion across regions and neighbouring countries [8].

Food chain and aquatic environment studies indicate that smaller fish feed on plankton, making them vulnerable to infection. The bacteria build up in their scales and stomachs, remaining active until reaching the fish market and up to several weeks later, even if refrigerated. Although infection is more likely to occur by drinking contaminated water, eating inadequately cleaned and cooked fish poses an equally significant health risk [8].

A higher, hidden risk is posed to those who are responsible for buying and cleaning the fish, primarily consisting of women and children. Observations revealed that hygiene measures during the gutting process are limited, with poor hand cleaning being the primary and most plausible cause of infection [9]. As women are involved in cleaning, descaling, smoking and selling fish in most of West Africa, they are particularly vulnerable to infection and can promote disease spreading to children. Official reports reflect that trend, with children making up to 80% of new infections in Sierra Leone’s Port Loko district [10]. The houses of these regions are mostly compounds, with a central courtyard for cooking, additionally used for many other household purposes, such as clothes and utensils washing, often leading to quick cross-contamination [5].

Ineffective sanitary reforms and lacking local progress to adequately apply the necessary by-laws on food hygiene, sanitation, environmental health and waste disposal, deem any effort to eradicate cholera unsuccessful [11]. Appropriate evaluation of disease transmission, vulnerable populations and strategies to adequately mitigate the cholera burden are crucial steps towards reducing incidence and preventing human loses. Cholera remains a dangerous reality for millions and needs to be addressed, holistically and comprehensively, as a disease of the present and the future.

Federico Paoletti is a third-year Systems Biology DPhil student at University College (University of Oxford), focussing on cancer research and primarily interested in applying data science and e-health to promote evidence-based interventions in global health.

Tom Rowland is a first-year medical student studying at the University of Oxford, primarily interested in global health the role of international cooperation in preventing pandemics

Vasileios Nittas is an MSc Student, reading Social and Health Policy at Green Templeton College (University of Oxford), primarily focusing on digital health policy and infectious disease prevention innovations.

References

[1] World Health Organization Global Task Force on Cholera Control, Cholera outbreak: Assessing the outbreak response and improving preparedness, (2004)

[2] Almagro-Moreno, S. and Taylor, R. K., Cholera: Environmental reservoirs and impact on disease transmission. Microbial Spectrum, (2013)

[3] World Health Organization, National cholera prevention campaign launched in Ghana, (2016)

[4] Ali, M. et al., Updated Global Burden of Cholera in Endemic Countries. PLOS Neglected Tropical Diseases, (2015)(

[5] Nelson, E. J. et al., Cholera transmission: the host, pathogen and bacteriophage dynamic, (2009)

[6] World Health Organization Global Task Force on Cholera Control, First steps for managing an outbreak of acute diarrhea, (2003)

[7] Mintz, E. D. and Tauxe, R. V., Cholera in Africa: a closer look and a time for action. Journal of Infectious Diseases, (2013)

[8] Useya, J., Simulating diffusion of cholera in Ghana (University of Twente, 2011)

[9] Scheelbeek, P., Treglown, S., Reid, T., & Maes, P., Household fish preparation hygiene and cholera transmission in Monrovia, Liberia. Journal of infection in developing countries, (2009)

[10] IRINNEWS, Cholera-Whats Working? (Dakar, 2012)

[11] Ofori-Adjei, D. and Koram, K., Of cholera and ebola virus disease in Ghana. Ghana Medical Journal (2014)