Simultaneous Cholera Outbreaks Emphasize Critical Need for Investment in WASH Infrastructure, Point to Impact of Climate Change

March 8, 2024
cholera outbreak in Zambia 2024

A worker carries a bucketful of disinfectant at a cholera treatment centre, in Lusaka, Zambia, Friday, Jan 12, 2024. The country is reeling from a major cholera outbreak that has killed more than 400 people and infected more than 10,000, leading authorities to order schools across the country to remain shut after the end-of-year holidays. (AP Photo)


By Kelly Jordan

The world is currently experiencing simultaneous outbreaks of cholera in southern Africa, parts of Asia, and the Middle East at unprecedented levels. Caused by the bacterium, Vibrio cholerae, people can contract the violent diarrheal disease by consuming contaminated food or water. In early 2023, the World Health Organization issued the cholera resurgence a level three emergency. In early 2024, numbers for the year were already surpassing 40,000 cases and more than 700 deaths.

Cholera isn’t something we hear about often in the United States, but that hasn’t always been the case. In the 19th century, there was a global cholera pandemic that killed millions of people around the world, including in the United States. Since then, the development of an effective two-dose oral vaccination, methodical disease surveillance, and investment in water, sanitation, and hygiene infrastructures has eliminated the threat of cholera in several countries, limiting the threat in industrialized nations like the United States. Cholera is now easily treatable with oral rehydration solution or IV fluids.

During World War II, Dr. Eugene Gangarosa, namesake of the Gangarosa Department of Environmental Health, conducted intestinal biopsy studies credited with the widespread adoption of rehydration therapy, which has dramatically influenced the standard operating procedure for treating cholera and saves approximately 1 million children a year. The Center for Global Safe Water, Sanitation, and Hygiene (WASH) at Rollins, founded by Gangarosa, continues to advance WASH-related research.

Despite the progress that has been made, prevention and disease mitigation in locations where a strong WASH infrastructure is absent—like those countries currently impacted— can be very difficult, especially when additional factors like climate change, political strife, and vaccine shortages compound the situation. 

David Berendes, PhD, co-team lead and epidemiology unit lead in the Global Water, Sanitation, and Hygiene Team at the U.S. Centers for Disease Control and Prevention (CDC), and alumnus of both the MSPH and PhD programs at Rollins, shared his insights on the current outbreaks and what they mean for global health.

Cholera is endemic in some of the countries currently experiencing outbreaks, but how does this series of outbreaks compare to those in previous years?

Since December 2021, we've been experiencing the worst global cholera situation in many years, maybe even in a decade or so. We have been seeing higher case loads and higher case fatality ratios in these cholera outbreaks than we've seen in the recent past. This is to some degree unprecedented in the recent past in terms of the amount of cholera occurring in the world.

What accounts for this increase in cases?

There are likely a couple of contributing factors. One is definitely climate-change related, but the other may be related to the global strategy for ending cholera. The goal was to use cholera vaccination as a stopgap medium-term measure. That [vaccine] offers three to five years of immunity. The idea was that during that time WASH improvements would be made in those countries. Vaccinations did happen around 2016, 2017, and 2018, but the WASH investment didn't keep up with where it needed to be. So I think that also is a contributing factor to why we're seeing this high volume of cases right now.

What steps is CDC currently taking with partners to help mitigate further spread and respond to these outbreaks?

CDC is a founding member of the Global Task Force on Cholera Control (GTFCC)’s Ending Cholera Initiative, which aims to reduce morbidity and mortality associated with cholera in key hotspot locations by 90% by 2030. We align with their pillars of epidemiology, laboratory, case management, vaccination, and WASH as core pillars to ending cholera. We are aligned on the Global Roadmap to 2030. We’re part of that initiative, and do both prevention work and outbreak response.

Within these current outbreak locations, we've been deploying subject matter experts directly to assist with case management, surveillance, vaccination, WASH, and response coordination. We've also assisted from afar from the U.S. by analyzing data. We’ve helped develop data dashboards and conduct trainings. And then finally, we also directly support partners including non-governmental groups like UNICEF and governmental entities as well to do rapid risk assessments, implement water quality monitoring campaigns, and conduct vaccine coverage assessments.

How can individual countries respond to the outbreaks?

Access to WASH is the underlying reason for these cholera outbreaks. It’s also the most important long-term solution to preventing and avoiding future outbreaks. The outbreaks are a direct result of sewage contaminating water systems that people drink and use. This is an area where, in the long term, we really want our development partners in WASH to align their investments on WASH for development purposes with the cholera hotspots identified in the Ending Cholera roadmap. In the short term, the key prevention measures we recommend and help countries with are really treating drinking water with chlorine, community education, and risk communication.

If people come to cholera treatment centers early and are rehydrated properly, more than 99% should not die of cholera. Vaccination is a complementary prevention measure, which can be effective in outbreak response if it's implemented soon after the outbreak is detected. The single dose of the cholera vaccine, which is what we're able to provide based on what is globally available due to the vaccine shortage, is still protective for at least 12 months in most groups. However, the basic WASH services are the solution to fixing this issue in the long term. Cholera is a very survivable disease, but we need people to have access to health systems if they get cholera, and then we need the WASH measures to prevent cases in the first place.

What role does climate change play in the quantity of outbreaks we’re seeing?

We know that climate change is an underlying factor that affects not only the pathogen spread, but also some people's exposure to it, such as through exposure to flood waters or contaminated drinking water. I think the other factor to think about with climate change is climate-associated disasters and the indirect effect of people being displaced because of climate and then being in camps where people congregate with poor water, sanitation, and hygiene.

How effective is the cholera vaccine? How are the CDC and other global organizations working together to help amp up vaccine production?

Two doses of the oral cholera vaccine are protective against cholera for at least three years, preventing about two out of every three cholera infections. However, because of the global shortage of vaccines, only one dose is being used in these outbreak responses, and that's to allow more outbreaks to be covered with existing vaccine availability. The downside of that is that one dose provides protection for only about a year, and among children, especially those under 5, the protection has been observed to be a bit lower for both the two and the one dose strategies. So it's a short-term measure in that respect that we're trying to use globally to cover as much as we can of the different outbreaks. Global vaccine partners have been working with the manufacturer to maximize production.

Is cholera ever a risk in the United States?

We occasionally see isolated cases of cholera in the U.S., however, most of that is travel associated. It's from people coming from areas that have cholera outbreaks. But given the strong WASH infrastructure we have here, the risk of local transmission or a cholera outbreak in the U.S. is exceedingly low.

How can neighboring countries to those currently impacted improve their defenses and prevent their own outbreaks?

The key prevention measures are really aligned with the GTFCC pillars I talked about. Having good health systems with cholera treatment centers able to rehydrate cases quickly will help maximize survival rates. Having quality surveillance systems to detect cases early and respond effectively is critical. This includes lab capacity to detect cases and monitor drinking water quality in countries to know if drinking water is contaminated. Finally, preventive vaccination followed by strong investment in comprehensive WASH infrastructure are the [ingredients needed for true prevention]. And that's the goal here. That the next time we have vaccines available and we're able to do preventive vaccination, we need that strong investment in WASH infrastructure with WASH partners investing in WASH in the key cholera hotspots in order to make sure that we fix this once and for all.