The World Health Organization reports there were 473 000 cases of cholera — an acute diarrheal disease that can kill within hours if untreated — in 2022. That is double the number from 2021, and it is estimated to have almost doubled again in 2023, now up to 700,000 cases. Currently, 23 countries are reporting cholera outbreaks, including the Democratic Republic of the Congo, Ethiopia, Mozambique, Somalia, Zambia and Zimbabwe.
Sabin asked Dr. Samuel Kariuki, Director of Drugs for Neglected Diseases (DNDi) Eastern Africa and Senior Principal Research Scientist at the respected Kenya Medical Research Institute (KEMRI), to explain the reasons behind increasing outbreaks of the waterborne disease and some of the current challenges faced by local responders.
What factors do you think are contributing to the widespread outbreaks of cholera?
Climate change is playing a huge role exacerbating the spread of cholera in low income settings. Frequent unpredictable weather including floods, drought and the resulting populations movement that result from these climate change factors contribute to more frequent outbreaks
Cholera is also a disease of poverty, and the low income countries are most affected by negative global trends that economically affect the most vulnerable. More people end up in poorer neighborhoods devoid of adequate WASH (safe drinking water, sanitation and hygiene) infrastructure, as they migrate from rural settings to urban settings looking for jobs and livelihoods.
There has not been enough attention given to cholera as a disease of pandemic proportion by governments and partners in low- and middle-income countries. Efforts towards improving WASH (which would also benefit prevention of many other infectious diseases) have been inadequately funded. There is now a turn around in Africa, arising mainly due to increasing incidence of outbreaks affecting even the middle income class in these settings, so more attention is now been given to these outbreaks.
Also, population growth is not matching growth in infrastructure, especially in urban settlements – this is driving more low-wage earners into informal settlements that are devoid of adequate water and sanitation, leaving these populations vulnerable to cholera and other water-borne infections.
Finally, pathogen evolution and environmental contamination plays a huge role in persistence and spread of the disease. There is a higher proportion of strains having acquired resistance to commonly available drugs, and persisting longer in the environment.
You have spoken in the past about antibiotic-resistant cholera. How quickly is cholera developing resistance, and what implications does this hold for treatment strategies?
Before 2012 we isolated less than 10% multi-drug resistant (MDR) V. cholerae strains. Now we see more than 70% with MDR and also extended spectrum beta-lactamases (ESBL) resistant strains. In a span of 12 years, the bacterium has changed its phenotype by acquiring a large mobile genetic element (plasmid) that is able to carry and spread the drug resistance genes even to other bacteria in the same environment and ecosystem.
Spread of resistance is therefore fairly rapid, and across different species of enterobacterales. We also see more environmental persistence of these drug-resistant strains.
In an outbreak situation, have you observed a change in attitudes towards cholera vaccines? Are people more receptive to vaccination efforts due to the perceived protection they offer?
There are more people now willing to have the cholera jab, than previously. I think what is driving this is that more people are now affected or have seen neighbors or friends affected by cholera and and now seek any solutions that will protect them and their families. We are seeing more persistent outbreaks even during the dry seasons of the year, and outbreaks also affected even some affluent areas of the cities and rural areas – this is causing more people to seek protection against cholera infections for their families.
The shortage of cholera vaccines is making headlines – how is the shortage of vaccines impacting the work on the front lines?
Vaccines are critically important as a frontline intervention to interrupt transmission, protect the most vulnerable people in the community and provide a window for public health players and other stakeholders to put in place longer term prevention and control measures including improving WASH conditions. Shortages of vaccine in our settings therefore directly affect the speed at which we can intervene in an active cholera outbreak and also leads to loss of opportunity for preventive campaigns that would save lives in settings where cholera is endemic, and just waiting for the right conditions to blow out into an epidemic.
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