Cholera in Bangladesh

The incidence of diarrhea remains high globally, although mortality has declined due to life-saving interventions such as oral rehydration solution. Despite the successes, the Global Burden of Disease Study ranked diarrheal diseases as the ninth leading cause of death globally, and the fourth leading cause in children under 5 years of age \citep{Gill2017}. In South Asia and sub-Saharan Africa, diarrheal illness accounts for at least 10% of deaths in children \citep{unicef}
The Global Task Force on Cholera Control (GTFCC) has recently launched ambitious goals for reducing cholera deaths by 90% by 2030 and eliminating cholera from at least 20 of the 47 high-burden countries, including Bangladesh \citep{Legros2018}. To achieve these objectives, the World Health Organization (WHO) has recommended the use of oral cholera vaccines (OCVs) together with other cholera prevention and control strategies. To ensure access to OCV for cholera-affected countries, a global OCV stockpile was created in 2013. However, the current global OCV supplies are too low for targeting all individuals living in countries at risk \citep{Ali2015}. Thus, countries with cholera need to identify and focus control efforts in high-risk populations. 
In Bangladesh, located in the heart of the Ganges Delta and considered to be the ancestral home of cholera \citep{barua1992}, the disease remains a significant public health problem \citep{Sack2003}. People live in high-risk, densely populated environments with poor access to safe water and sanitation \citep{Islam2018}. It is suggested that 66 million people are at risk of cholera in Bangladesh, with an incidence rate of 1.64/1000 population, 100 000 cases, and 4500 deaths annually \citep{Ali2015}. These estimates were only obtained from population-based published studies to estimate the annual number of cases. Bangladesh is developing a national cholera-control plan in order to meet objectives set forth in the GTFCC Roadmap. It was therefore crucial to determine the magnitude of cholera to obtain information on seasonality and location of prevalent areas in Bangladesh. Based on this need, a nationwide enteric disease surveillance with laboratory confirmation was initiated in 2014, which covered all divisions across the country. The objective was to understand the epidemiology of cholera throughout Bangladesh.
Cholera, a deadly waterborne diarrheal illness caused by toxigenic Vibrio cholerae species, is more prevalent in developing countries such as Bangladesh due to use of unsafe drinking water with poor sanitation \citep{Clemens2017}. The burden of cholera is very high in Bangladesh, with an estimated ~100,000 cases reported annually and close to 4,500 deaths per year \citep{Ali2015}