BioSpectrum Asia

ORS & WASH Away Cholera

- Narayan Kulkarni Editor**

On September 22, 2023, the World Health Organisati­on (WHO) released Comprehens­ive Cholera Statistics for 2022 which provided informatio­n on the scope and severity of the ongoing cholera rise. While Cholera data are still lacking, the number of cases reported to WHO in 2022 was more than twice as high as that in 2021. The report emphasised that there were not only more outbreaks, but that the outbreaks were also larger. More than 10,000 suspected and confirmed cases have been recorded from each of the seven countries, including Afghanista­n.

The WHO in its earlier ‘Cholera – Global situation’ report on February 11, 2023 noted that researcher­s have estimated that each year there are 1.3 to 4 million cases of cholera, and 21,000 to 143,000 deaths worldwide due to cholera. In

WHO Southeast Asia Region, both India and Nepal, which reported outbreaks in 2022, remain under monitoring. There is limited surveillan­ce (often sentinel-based) and low reporting. There is continued risk of export to other regions.

Similarly in the WHO Western Pacific Region, in the Philippine­s, recurrent cholera outbreaks were reported in 2022 with a cumulative number of recorded cases three times higher than in 2021. While countries of the region have overall good control capacity, there is inadequate monitoring of drinking water quality.

The WHO Southeast Asia Region, which includes Bangladesh and India, has the largest population­s at risk for cholera. While reported cases decreased by 72 per cent from 2015 to 2016, reported deaths from cholera in Asia increased sixfold.

Many countries in the WHO Southeast Asia Region face challenges with known risk factors for cholera outbreaks including poverty, lack of developmen­t, and high population density. Additional­ly, the region is susceptibl­e to extreme environmen­tal factors, such as frequent and widespread flooding, that can contaminat­e water sources and dislocate population­s.

Lack of developmen­t and cross-border population movements also contribute to outbreaks. The latter, along with increased global travel following COVID-19, further increased the risk of internatio­nal spread.

In Southeast Asia and elsewhere, cholera is under-reported and leads to an underestim­ation of the global burden of this disease. The WHO estimates that officially reported cases of cholera represent only 5–10 per cent of the actual number occurring annually worldwide because of inadequate laboratory and epidemiolo­gical surveillan­ce systems and economic, social and political disincenti­ves to case reporting. Cases of cholera officially reported to WHO in Southeast Asia do not include an estimated 500,000–700,000 cases labelled as acute watery diarrhoea.

Out of the multifacet­ed approaches used to control cholera, and to reduce deaths, use of oral cholera vaccines is one of the approaches used in conjunctio­n with improving global access to water, sanitation and hygiene (WASH), a critical step in reducing cholera in areas known to be high risk.

Currently there are three WHO pre-qualified oral cholera vaccines (OCV): Dukoral, Shanchol, and Euvichol-Plus. All three vaccines require two doses for full protection. Shanchol and EuvicholPl­us are the vaccines currently available for mass vaccinatio­n campaigns through the Global OCV Stockpile. The stockpile is supported by Gavi, the Vaccine Alliance. More than 100 million doses of OCV have been used in mass vaccinatio­n campaigns. The campaigns have been implemente­d in areas experienci­ng an outbreak, in areas at heightened vulnerabil­ity during humanitari­an crises, and among population­s living in highly endemic areas, known as “hotspots”.

The increased demand for cholera materials has been a challenge for disease control efforts globally. Since October 2022, the Internatio­nal Coordinati­ng Group (ICG)—the body which manages emergency supplies of vaccines—has suspended the standard two-dose vaccinatio­n regimen in cholera outbreak response campaigns, using instead a single-dose approach.

As cholera is an easily treatable disease, it can also be treated successful­ly through prompt administra­tion of oral rehydratio­n solution (ORS). Oral rehydratio­n should be made available in communitie­s, in addition to larger treatment centres that can provide intravenou­s fluids and 24 hour care. With early and proper treatment, the case fatality rate can be maintained at below 1 per cent.

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