Cholera pandemics first emerged in the 19th century from the Ganges delta in India. The bacteria Vibrio Cholerae (V. cholerae) spread, leading to global pandemics that have killed millions of people. The current seventh global cholera pandemic began in 1961, spreading to Africa in the 70s and the Americas in the 90s and has become endemic in many countries in southeast Asia and Africa. In 2022, 29 countries reported cholera outbreaks to the WHO.
In Africa, Malawi has reported its worse cholera outbreak in decades. Since March 2022 there have been over 1000 cholera related deaths. In 2023 the cases have continued to rise.
In the Americas, the 2010 cholera outbreak in Haiti resulted in over 800,000 cases and 10,000 deaths. Twelve years later in February 2022 Haiti was declared cholera free. Unfortunately, by September 2022 cholera had returned. Two fatal cases were reported and confirmed to be V. cholerae O1 with sequence analysis showing similarity to the strain responsible for the 2010 outbreak. To date there have been over 20,000 suspected cases, >400 deaths and a case fatality rate of 3%. Worsening political instability is an important contributor to the outbreak.
Cholera is an acute diarrheal infection caused by the bacterium V. cholerae O1 and O139 strains. Most individuals who are infected are without symptoms or have mild symptoms enabling the disease to spread silently through communities. As many as 20% of cases will develop symptoms and many can be treated with rehydration solutions. Symptoms may manifest in a few hours, and clinical deterioration and death can occur rapidly. Timely introduction of effective treatment can reduce case fatality from >50% to the desired goal of <1%.
Cholera outbreaks reflect broad systems failures. Significant investments in development, infrastructure, health facilities and climate resiliency are necessary to prevent future outbreaks. Investments in water and sanitation infrastructure have contributed to the eliminating cholera in Europe and North America. Without access to safe drinking water and appropriate sanitation, diarrheal diseases such as cholera cannot be eliminated. The United Nations Sustainable Development Goal 6 (SDG6) declares a commitment to ‘ensure availability and sustainable management of water and sanitation for all’. However, access to on-premise water is on average 39% across Africa. In many countries on-premise water access is as low as 2-5% in rural communities. Even when water is on-premise in urban settings, it is not consistently available, is not treated and often is not safe to drink. In 2020, 2 billion and 3.6 billion people lacked safely managed water or sanitation services respectively. Ending open defecation, improving water quality and treatment of wastewater are critical to enable significant global strides towards achieving SDG6 and reducing diarrheal diseases such as cholera.
In addition to poor infrastructure, lack of accountability for water and service provision and political instability, climate change is a major contributor to current cholera outbreaks. Countries with high levels of poverty and poor infrastructure are susceptible to the adverse effects of climate change such as droughts and flooding. In southern Africa the rise in cyclones such as cyclone Gombe in March 2022, tropical storms and associated flooding in Mozambique and Malawi are important contributors. In times of drought, limited access to drinking water leads to use of unsafe water supplies. Tackling climate change and providing knowledge and tools to achieve climate resiliency for communities will be critical in curbing future local and global pandemics.
Vaccines remain our most effective tools against infectious diseases such as cholera. Vaccines are highly effective in the control of cholera outbreaks. The first injectable vaccine was developed in 1885 and several others followed. These injectable vaccines were not suitable for mass vaccination public health programs due to limited efficacy and reactogenicity. In 2001 the first oral cholera vaccine was developed in Sweden and licensed as Dukoral® in 1991. It is highly effective but is expensive and needs to be administered with a buffered solution. Its use is currently limited to travelers from high income settings. Global partnerships with local vaccine manufacturers in Vietnam and India facilitated technology transfers and improvements in vaccine immunogens resulting in the WHO prequalification of two low-cost vaccines in 2009 (mORCVAX™) and 2011 (Shanchol ®). To further expand capacity to meet global demand for cholera outbreaks, technology transfer was made to a South Korean biologics manufacturer resulting in WHO prequalification for Euvichol® in 2015. These vaccines cover the V. cholerae O1 and O139 strains and have made vaccines affordable for mass vaccination programs.
Cholera is an ancient disease that takes advantage of political instability and climate change to cause significant disease and disruption in vulnerable communities. As the world thinks about pandemic preparedness it is tempting to focus on the ‘unknown unknowns’ (unknown emergent pathogens) or the ‘known unknowns’ (members of pathogen families that can be studied providing a blueprint on how to respond to novel family members). But for many of the world’s vulnerable populations the ‘known knowns’ provide the greatest immediate threats. These include diseases such as cholera, typhoid, malaria, TB, and drug resistant bacteria. As mass vaccination campaigns progress in Malawi and Haiti perhaps it is time to focus resources on investments that improve access to safe drinking water, stimulate innovations in water, sanitation and hygiene (WASH) service delivery, strengthen capacity in Africa for vaccine and pharmaceutical manufacturing to meet the continents needs and build resiliency in communities most at risk of infectious diseases as a result of climate change.
References/Additional reading
Vega, Ocasio D, Juin S, Berendes D et al. Cholera Outbreak – Haiti, September 2022-Jan 2023 MMWR Morb Mortality Wkly Rep 2023; 72:21-25
https://www.weforum.org/agenda/2022/water-accessibility-divide-sub-saharan-africa-visualized
Progress on Household drinking water, sanitation, and hygiene (2000-2020). WHO/UNICEF Joint monitoring program for water supply, sanitation, and hygiene.
https://climateknowledgeportal.worldbank.org/country/mozambique
Author: A. Tariro Makadzange, MD PhD is an infectious disease physician and viral immunologist, and founder of CRMG and Mutala. CRMG and Mutala are focused on conducting clinical trials, public health and basic science research to address medical issues pertinent to Africa. Reviewed and edited by Tashinga Chigodora.