Shrinking the Cholera Map
I first witnessed the devastation that cholera can cause on my first trip to Bangladesh in 1974. I had arrived to work on a different cause of diarrhea, enterotoxigenic E.coli, but around me a major humanitarian crisis was in full force. Famine and flood had uprooted thousands; people were living on the streets and cholera ran rampant. At that time, I learned how the groundbreaking oral rehydration treatment, recently developed in India and Bangladesh, could save the lives of all cholera patients by preventing dehydration through fluid replacement.
Yet in areas of the world where this lifesaving treatment is not available, thousands of people die. In fact, globally, more than 2 million people contract cholera each year and approximately 95,000 die from the disease, mainly in Asia, Sub-Saharan Africa and Haiti.
Clearly, treating cholera after it strikes is not enough. With the new tools we’ve developed in the decades since my trip to Bangladesh—and with enough global will—I believe we can reduce the number of people affected by cholera each year and shrink the cholera map. Some recent developments are extremely exciting for those of us involved in cholera control:
Oral Cholera Vaccine (OCV) Is Becoming More Widely Available.
OCV is an essential component of cholera prevention and control, alongside water, sanitation and hygiene, or WASH, initiatives. The vaccine can decrease the severity of an outbreak, reduce rates of disease in endemic settings, and prevent cholera from occurring in the first place during humanitarian crises and emergencies.
But OCV’s limited availability has curtailed its usefulness. Countries and NGOs can only acquire the vaccine through a global stockpile, established by the WHO with support from Gavi, the Vaccine Alliance. The stockpile has, until recently, annually offered 2 million doses (for a 2-dose regimen), targeted toward outbreaks—in other words, emergencies.
So it was great news in January when the WHO announced the addition of a new manufacturer with enough doses to boost the number available to 6 million a year, with plans for larger amounts in the near future.
The increased supply will greatly improve the ability to effectively respond to cholera outbreaks. And perhaps even more important, more OVC means cholera vaccination programs can shift their emphasis away from only responding to emergencies. Using enhanced surveillance and operations research to map high-risk “hotspots,” as well as predictions by local officials about when high season is likely to occur, these programs will be able to use OVC to prevent outbreaks before they occur.
And We’re Learning How to Use OVC More Effectively.
For example, we now know that a single dose of OVC provides sufficient protection in the short term. But we need to learn when and where this single-dose strategy is appropriate.
If 2 doses do provide better protection over the long run, the optimal interval between doses also needs to be better understood. Currently, those giving the vaccine schedule the second dose 2 weeks after the first. But it’s possible that a longer interval may be better or logistically more convenient.
We also know that cholera control is best when OCV is integrated with improvements in water and sanitation, but researchers still need to develop the exact ways in which these interventions should be integrated for best effect.
We need to challenge ourselves to consider how to improve the vaccine and improve strategies for its use. Would cholera control benefit from a vaccine that is even less expensive and more convenient to transport and administer, such as a heat stable tablet vaccine in a blister pack?
I’m incredibly optimistic about the direction cholera control is taking. While we cannot add cholera to the list of eradicable diseases, it is certainly one that can be significantly reduced to a level where it is no longer a major public health problem as it is today.
David A. Sack, MD holds a joint appointment in medicine at the Johns Hopkins University School of Medicine. He is a professor of international health in the Center for Global Health with a joint appointment in epidemiology at the Johns Hopkins School of Public Health.
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