The West African situation
Increased virus circulation among insufficiently immunized populations in combination with the region’s rampant urbanization set the scene for an explosion of urban epidemics. This situation is aggravated by spontaneous or forced migrations of unprotected people to areas at risk.
In Africa, since 2000, 18 countries have reported yellow fever. West Africa is the most affected region, with 13 (72%) countries burdened.
In West Africa, since 2000, 13 of the 14 (93%) countries with at least one case of yellow fever notified since 1950 have regularly reported cases (see charts below) and faced outbreaks. The 14 countries at risk of yellow fever transmission in West Africa are : Benin, Burkina Faso, Côte d’Ivoire, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Mali, Mauritania, Nigeria, Senegal, Sierra Leone and Togo.
The resurgence of the disease in West Africa mainly affects countries whose populations have gradually lost the protection provided by the mass preventive immunization campaigns carried out between 1933 and 1961, such as Benin, Burkina Faso, Côte d’Ivoire, Guinea, Senegal and Togo.
Although the number of cases is low, this situation is of great concern given that the number of reported cases underestimates the real magnitude of the problem.
The reported cases are only the severe cases who seek cure in medium size public health care facilities (maximum 1-2 % of the infected people in non epidemic period). Therefore the underestimation of the number of cases depends on many factors such as access to the health care system, sensitivity of the surveillance system, laboratory capacity to confirm cases and the willingness of the country to report a disease with potential negative impact on travel and tourism.
Moreover, four of the West African countries at risk of yellow fever are currently considered to be in a complex emergency situation (Côte d’Ivoire, Guinea, Liberia, Sierra Leone). This has a two-sided impact on the epidemiology of yellow fever: first of all, the humanitarian crisis prevents routine immunization programmes from being carried out, and secondly, the conflict is responsible for forced migrations of thousands of people, amplifying the potential virus circulation. In these circumstances, the response to an epidemic calls for greater coordination between the national health authorities and partners (NGOs and international organizations).
Multiple outbreaks may occur at the same time in many different places stressing the response capacity of the country and overwhelming the support capacity of the international community.