Number of reported cholera cases
In 2011, a total of 58 countries from all continents reported 589 854 cases of cholera to WHO, of which 32% were reported from Africa and 61.2% from the Americas where a large outbreak that started in Haiti at the end of October 2010 also affected the Dominican Republic. Globally, however, the true number of cholera cases is known to be much higher. Cases of cholera officially reported to WHO do not account for the estimated 500 000–700 000 cases labelled as acute watery diarrhoea. These cases occur in vast areas of Central and South-East Asia, and in some African countries, leading to great underestimation of the global burden of this disease. The discrepancy results from underreporting and other limitations of surveillance systems, including inconsistencies in case definitions and the lack of a standard vocabulary. Some countries report only laboratory-confirmed cases, although many more cases are consistent with WHO’s standard case definition of cholera.
In 2011, 32% of cases were reported from Africa whereas between 2001–2009, 93% to 98% of total cases worldwide were reported from that continent. It is the second year in a row that such a low proportion of cases has been reported from the African continent. This was already the case in the early nineties shortly after the 7th pandemic had reached the south American continent in 1991. Globally, cholera incidence has increased steadily since the year 2005 with outbreaks persisting in Sub-Saharan Africa, Asia and more recently in Hispaniola. Cholera continues to pose a public health problem among developing world populations without access to adequate water and sanitation resources.