Cholera is a water-borne disease caused by two strains called O1 and O139 of the bacteria Vibrio cholerae . Of these, O1 is responsible for almost all outbreaks; outbreaks of O139 are rare and none have been recorded outside Asia. According to the World Health Organization (WHO)’s weekly epidemiological record, published on September 22, the world reported more than twice as many cholera cases in 2022 as it did in 2021 (Chart 1). Between these years, more than twice as many countries also reported at least 10,000 suspected as well as confirmed cases of cholera.
Chart 1 | The chart shows year-wise reported cholera cases between 1989 and 2022.
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Both these trends suggest a reversal of a short-term trend, of declining prevalence since 2019. The reversal also complicates a target the WHO specified in 2017, to reduce the number of cholera deaths worldwide by 90% by 2030. According to the United Nations health body, “Cholera transmission is closely linked to inadequate access to clean water and sanitation facilities.” Vibrio cholerae bacteria also favour warmer waters with lower salinity. All these conditions are created as a result of climate change — which increases the likelihood of floods, heatwaves, intense monsoonal rains and storms, and the duration of warm periods — and war.
The epidemiological record report blames the uptick on the decline of the COVID-19 pandemic, and its restrictions; “limited investments” in providing care to those most vulnerable to the disease; the effects of climate change; and increasing conflict.
A 2021 study published in the journal The Lancet Planetary Health concluded that the length of the coastline favourable to the development of Vibrio bacteria could increase by 38,000 km by 2100 over the 1850-2014 average, in the SSP5-8.5 emissions scenario.
A June 2023 study by researchers at the University of Florida found that “ Vibrio pathogens have a unique ability to ‘stick’ to microplastics, and that these microbes might be adapting to plastic”, including in the open ocean, according to a statement by the National Science Foundation.
In response to the world’s growing cholera burden, and while waiting for investments in manufacturing to bear fruit, the body that manages the emergency stockpile of the oral cholera vaccine shrank the recommended vaccination regime from two doses to one.
Chart 2 | The chart shows year-wise cholera cases reported to the WHO across continents.
According to the report, most cholera cases continue to be reported from Africa and Asia, with Europe accounting for a few “imported cases” (Chart 2 and Map 3).
Map 3 | The map shows the country-wise reported cholera deaths and imported cases in 2022.
In Africa, cases were more spread out in 2022 than they were in 2021, which the report qualifies as no single country having reported more than 25% of all cases and 30% of all deaths. The report also says that between 2021 and 2022, the continent reported 29% fewer cases and 52% fewer deaths. This isn’t the good news it appears to be: in 2021, Nigeria had a large cholera outbreak that accounted for 78% of all cases in Africa that year. But in 2022, both the numbers of cases and of deaths in all the other countries (that reported data) more than doubled. Cameroon and Malawi in particular reported over 5,000 cases after more than a decade. Similarly, in Asia, both Lebanon and Syria have reported cases at all for the first time in a decade. Yemen had reported nearly 90% of the cases in West Asia in 2021 but didn’t report data in 2022. In Afghanistan, more than half of all cases were among those aged five years.
But there is one silver lining: whereas 20% of the countries that declared cases in 2021 reported using rapid diagnostic tests, 56% did so in 2022.
Source: World Health Organization (WHO)’s weekly epidemiological record
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