Yellow fever is a viral hemorrhagic disease transmitted by infected Aedes aegypti mosquitoes. The number of cases has increased over the past 20 years due to declining population immunity, deforestation, urbanization, population movements, and climate change. The World Health Organization (WHO) estimates that there are 200,000 cases of yellow fever and 30,000 deaths every year, 90% of which occur in Africa.
Once the virus has been contracted, it incubates in the body for three to six days, followed by infection that can occur in one or two phases:
- An acute phase with high fever followed by muscle pain, loss of appetite, nausea or vomiting. In 75% of cases, the individual’s health subsequently improves and his or her symptoms may disappear within four days.
- A toxic phase may occur within 24 hours of remission of the initial phase. The symptoms are severe fever, jaundice, and hemorrhages causing blood to appear in the vomit. Half of the people affected by the toxic phase die within 10 to 14 days.
As there is no treatment for yellow fever, preventive vaccination is crucial. WHO recommends routine infant immunization as well as mass vaccination campaigns in high-risk areas together with measures to control the Aedes aegypti mosquito in urban centers.
The GAVI Alliance has been providing support for increased yellow fever immunization coverage since 2007. One of the conditions for receiving funding is to implement AEFI (Adverse Events Following Immunization) surveillance. In this context, AMP supports yellow fever AEFI surveillance in collaboration with other organizations.