Cholera context

Disease Burden Worldwide and in Africa

Cholera is endemic in 51 countries, according to the 2005 United Nations population data and the Millennium Development Goal Indicators database. To be considered endemic, cholera must have been reported for at least three out of the last five years.

Although cholera has disappeared as a public-health problem in developed countries, it remains a major concern in sub-Saharan Africa. According to the World Health Organization (WHO) Global Health Observatory, the 30 affected African countries reported 98% of all cholera cases and 99% of all deaths in 2009 with an average case fatality rate of 2.25%.

The number of suspected cholera cases reported to the WHO every year is nearly 200,000, with around 5,000 deaths. However, these numbers are thought to be misleading due, in part, to underreporting and limitations in surveillance systems. The true global cholera burden is estimated to be three to five million cases with 100,000 to 120,000 deaths annually.

Challenges to Effective Surveillance

Efficient surveillance is key for detecting cholera outbreaks, controlling cholera in endemic areas, and reducing deaths. However, in many sub-Saharan African countries, surveillance capacity is limited, which results in the underestimation of true disease burden.

Reporting cases is complicated for various reasons, such as individual and community fears of stigmatization and economic loss. Furthermore, according to WHO, only 3% to 5% of all cases are laboratory confirmed. A variety of case definitions are used across countries, which could lead to cholera over- or under-reporting. 
Affected countries have attempted to cope by using syndromic case definitions, as proposed by WHO, and declaring all acute cases of diarrhea in children less than five years as cholera once a single case is confirmed in an endemic area (e.g., village, town, district).

But this practice is not ideal as it may lead to the overestimation or underestimation of cholera burden. In general, underestimation is the result of two main issues:

Prevention and Control

Measures for the prevention and control of cholera depend on the local context. In general, interventions include improvements in infrastructure, such as water and sanitation, and community education, but this is not happening quickly. In other parts of the world the international community is making a concerted effort to improve water and sanitation infrastructure, but no such initiatives are in sight for Africa.
Recently, a new generation of effective and affordable vaccines has opened new possibilities for short- to mid-term cholera control. To determine which interventions are the most efficient within a given context, accurate epidemiological data is needed. 

Since the Haiti epidemic during 2010, however, public and political attention on cholera has increased. Recently, WHO has prequalified a two-dose oral cholera vaccine (OCV) that is less expensive and less cumbersome to deliver than its predecessor. This, and the creation by WHO of a cholera vaccine stockpile for epidemic and potentially endemic cholera prevention, have stimulated interest in more timely, accurate, and comprehensive disease burden data from affected countries.