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Background Starting in 2008, the Central African Republic (CAR) experienced an unprecedented number of reported yellow fever (YF) cases. A risk assessment of YF virus (YFV) activity was conducted to estimate potential disease risk and vaccine needs. Methods A multistage cluster sampling design was used to sample humans, non-human primates, and mosquitoes in distinct ecologic zones. Humans and non-human primates were tested for YFV-specific antibodies; mosquitoes were tested for YFV RNA. Results Overall, 13.3% (125/938) of humans were found to have naturally-acquired YFV antibodies. Antibody levels were higher in zones in the southern and south central regions of CAR. All sampled non-human primates (n=56) were known YFV reservoirs; one tested positive for YFV antibodies. Several known YF vectors were identified including Aedes africanus, Ae. aegypti, Ae. luteocephalus, and Ae. simpsoni. Several more urban locations were found to have elevated Breateau and Container indices for Ae. aegypti. Conclusions A country-wide assessment of YF risk found YFV to be endemic in CAR. The potential for future YF cases and outbreaks, however, varied by ecologic zone. Improved vaccination coverage through mass campaign and childhood immunization was recommended to mitigate the YF risk.

Background The causative agent of yellow fever is an arbovirus of the Flaviviridae family transmitted by infected Aedes mosquitoes, particularly in Africa. In the Central African Republic since 2006, cases have been notified in the provinces of Ombella-Mpoko, Ouham-Pende, Basse-Kotto, Haute-Kotto and in Bangui the capital. As the presence of a vector of yellow fever virus (YFV) represents a risk for spread of the disease, we undertook entomological investigations at these sites to identify potential vectors of YFV and their abundance. Findings Between 2006 and 2010, 5066 mosquitoes belonging to six genera and 43 species were identified. The 20 species of the Aedes genus identified included Ae. aegypti, the main vector of YFV in urban settings, and species found in tropical forests, such as Ae. africanus, Ae. simpsoni, Ae. luteocephalus, Ae. vittatus and Ae. opok. These species were not distributed uniformly in the various sites studied. Thus, the predominant Aedes species was Ae. aegypti in Bangui (90.7 %) and Basse-Kotto (42.2 %), Ae. africanus in Ombella-Mpoko (67.4 %) and Haute-Kotto (77.8 %) and Ae. vittatus in Ouham-Pende (62.2 %). Ae. albopictus was also found in Bangui. The distribution of these dominant species differed significantly according to study site (P Aedes mosquitoes analysed by polymerase chain reaction contained the YFV genome. Conclusion The results indicate a wide diversity of vector species for YFV in the Central African Republic. The establishment of surveillance and vector control programs should take into account the ecological specificity of each species.

International audience; SUMMARY METHODS: Mosquito aquatic stages were collected in domestic and peri-domestic areas, and epidemic risk indexes (Breteau, Container) were calculated for each prospected location. Adult female mosquitoes were captured by human landing catches, while larvae were sampled by inspecting artificial and natural breeding sites in randomly selected premises. RESULTS: Seventy-eight adults Aedes albopictus were collected in Bangui and Bayanga. Mosquito biting rate and abundance were, respectively, 0.33-1.70 bites/human/hour and 14.6% in Bangui and 0.04-0.16 and 0.4% in Bayanga. Larval sampling revealed a large diversity of water container harbouring the species in Bangui, Bayanga, Nola and Salo including unused containers, old tires, vehicle carcasses, buckets, barrels and stem of bamboo. The epidemic risk indices were erratic according to the location, ranging between 1.5-27.6 for Breteau and 1.3-47.1 for Container. CONCLUSION: This is the first record of Ae. albopictus in two bioclimatic zones of CAR This observation emphasizes the need to further investigate its potential impact on dengue and chikungunya viruses transmission regarding their recent emergencies in Africa (Côte d'Ivoire, Senegal, Mali, Somalia, Gabon, Cape Verde Islands).