Background: Yellow fever (YF) is an acute infectious viral disease transmitted by Aedesmosquitoes that causes 200,000 human cases and 30,000 deaths annually in tropical Africa and South America. Human cases follow periodic emergence YF virus (YFV) from its sylvatic cycle in non-human primates. In Senegal, the Kedougou region is an emergence zone where amplifications of sylvatic YFV have been reported at 4 to 6 years interval. Since 2007, gold mining has become the main economic activity in Kedougou and has led to increased urbanization, more activity in the forest and massive immigration of non-immune populations. In association with these disruptions, a YF outbreak occurred in Kedougou in 2010. In this paperwereport epidemiological, virological and entomological information about this outbreak. Methods & Materials: An human surveillance of Acute Febrile illnesses were implemented in 7 clinics in Kedougou region. Also entomologic andmonkeysurveys were carried out in thesamearea. Human and monkey samples were tested for YFV- PCR and IgM and IgG YF antibodies by ELISA. Mosquitoes were sorted in monospecific pools and tested by YFV RT-PCR. Results: From January 2010 to December 2011 9,213 patients were enrolled and 13 were confirmed as YF (0.14%), including 12 IgM antibody positives, and 2 PCR positive and 10 probable cases. Three thousand four hundred and seventy seven (3,477) and 1,793 mosquito pools were respectively collected and tested for YFV by PCR and virus isolation in 2010 and 2011. YFV was detected in 67 pools of mosquitoes (1.9%). Additionally, 378 monkeys were screened for anti-YFV IgM and neutralizing antibody; one monkey sample presented anti-YFV IgM, and seroprevalence of YF neutralizing antibodies among juvenile monkeys increased from 4 to 42% between 2010 and 2011. Entomological investigations during the YF outbreak revealed that Ae. aegypti was present in all localities;Aedes furcifer was the predominant species and Breteau indexes were well above the epidemic threshold. Conclusion: Increased urbanization and migration of susceptible populations may favor adaptation of Ae Aegypti to domestic context and the presence of infected Aedes furcifer that would lead to intermediate or urban transmission of YFV.
Sow, A., Ba, Y., Diallo, D., Omar, F., Ousmane, F., Kathryn, H., … Alpha, S. A. (2014). Re-emergence of yellow fever in Kedougou, Southeastern Senegal in 2010-2011. International Journal of Infectious Diseases, 21, 219. https://doi.org/10.1016/j.ijid.2014.03.878