Cholera – Cameroon - ISS-G20 Laboratorium Repository

Epidemiology of Cholera

Cholera is an acute enteric infection caused by ingesting the bacteria Vibrio cholerae present in contaminated water or food. It is mainly linked to insufficient access to safe drinking water and inadequate sanitation. It is an extremely virulent disease that can cause severe acute watery diarrhoea resulting in high morbidity and mortality, and can spread rapidly, depending on the frequency of exposure, the exposed population and the setting. Cholera affects both children and adults and can be fatal if untreated.

The incubation period is between 12 hours and five days after ingestion of contaminated food or water. Most people infected with V. cholerae do not develop any symptoms, although the bacteria are present in their faeces for 1-10 days after infection and are shed back into the environment, potentially infecting other people. Among people who develop symptoms, the majority have mild or moderate symptoms, while a minority develop acute watery diarrhoea with severe dehydration. Cholera is an easily treatable disease. Most people can be treated successfully through prompt administration of oral rehydration solution (ORS).

Cholera can be endemic or epidemic. A cholera-endemic area is an area where confirmed cholera cases were detected during the last three years with evidence of local transmission (cases are not imported from elsewhere). A cholera epidemic can occur in both endemic countries and in non-endemic countries.

The consequences of a humanitarian crisis – such as disruption of water and sanitation systems, or the displacement of populations to inadequate and overcrowded camps – can increase the risk of cholera transmission, should the bacteria be present or introduced. Uninfected dead bodies have never been reported as the source of epidemics.

Cameroon is among several countries in West and Central Africa experiencing recurrent cholera outbreaks. Several risk factors including circulation of Vibrio cholerae especially in the North, Littoral, Central, and South-West regions, limited access to safe drinking water in some areas including in the capital city of Yaoundé, as well as cultural practices that contribute to unsafe WASH conditions exist in the country. There is a seasonal pattern of cholera occurrence in Cameroon that varies by region.  In South-West and Littoral, currently the most affected regions, cholera is most often reported during the rainy season (November - April) or the transition between the rainy and the dry season. In the Central region, cholera is more frequently reported during the rainy season that occurs in May-June and October-November. The ongoing rainy season may increase the likelihood of further transmission in the country.

In addition, some affected areas of the country are insecure which further reduces the access to services making outbreak response more complex.

The cholera outbreak began surging in late October 2021, deteriorated further in March 2022 with the South-West region reporting 70% of cases. Limited geographic accessibility of some areas, security constraints, and suboptimal communication networks lead to irregular epidemiological updates and potential underreporting of cases. Additionally, high population movement of Internally Displaced Persons (IDPs), weak health system, insufficient human resources, poor knowledge of treatment protocols and low risk communication for cholera continue to pose challenges.

Furthermore, in the northern areas, Cameroon is bordered by Adamawa, Borno and Taraba states of Nigeria and there is frequent and substantial cross border movement posing a risk of transmission. There is also a risk of further international spread especially to the Republic of Chad which borders both Nigeria and Cameroon.