Epidemiology
Cholera is usually a disease occurring in the context of poverty, war, or displacement, affecting individuals in resource-limited settings with limited access to clean water sources; however, it is also a disease well described in returning travelers.[9] It is thought to be endemic in a wide range of countries, mostly in Africa and Asia.[10] According to the World Health Organization (WHO), in 2022, nearly half a million cases of cholera were reported worldwide, more than double the number of cases reported in 2021.[11][12] The number of countries reporting cholera cases and outbreaks also rose, from 35 in 2021 to 44 in 2022. Among the 44 countries reporting outbreaks, seven countries (Afghanistan, Cameroon, the Democratic Republic of the Congo, Malawi, Nigeria, Somalia, and Syria) reported large outbreaks affecting 10,000 people or more. Overall, 472,697 cases and 2349 deaths from cholera were reported in 2022, with a case-fatality rate of 0.5%.
Despite epidemiologic reporting from the WHO, there still remains substantial underreporting of cholera, particularly in resource-limited and conflict-ridden countries with limited detection and reporting structures.[13] Estimates suggest that approximately 1.3 to 4.0 million cases of cholera occur annually worldwide, with 21,000 to 143,000 deaths.[14] While large outbreaks are often a result of war and natural disasters, annual rates of infection have shown seasonal patterns coinciding with warmer ambient temperatures.[15] Peaks of disease are seen episodically but usually tend to coincide around the world.[16]
Major outbreaks have been reported in Afghanistan and in several countries in the Middle East.[11] Yemen had more than 1 million suspected cases between 2017 and 2018 in the context of conflict and war. Global Taskforce on Cholera Control: cholera outbreak response Opens in new window
In Haiti, following the 2010 earthquake that displaced more than 1 million people, 820,000 cases of cholera were reported up to February 2019.[17] After being declared free from cholera in 2019, the country began experiencing a new outbreak from October 2022.[18] Local cholera transmission has also been reported in the neighboring countries of the Dominican Republic, Cuba, and Mexico.[9]
Cholera is rare in the US with 10 cases reported in 2018, 8 of which were imported.[19] Few cases are also seen in Europe, with 51 cases reported in 2022, 47 of which were imported.[11]
In endemic regions, the highest rates of infection are in children under the age of 5 years. In nonendemic areas, adults are equally as affected as children. There is no overall sex difference in incidence but, early in an epidemic, males are often affected disproportionately. This is due to higher rates of water exposure because of working patterns. Attack rates are high, although only a small proportion of those exposed will become seriously ill (about 1% to 5%).[20] The clinical picture depends upon bacterial load and patient factors such as the degree of background immunity, and the presence or absence of malnutrition.
There is evolving evidence that major genetic changes in the pathogen may result in a clinical course of increased severity. In two Asian outbreaks, Vibrio cholerae O1 was determined to be El Tor in phenotype, but harbored a classical cholera toxin biotype. The implications of this are important: cholera caused by strains that result in increased disease severity may result in increased deaths if it spreads to areas with poor treatment facilities.[5]
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