Circulation of Dengue Virus Type 3 Genotype III in Africa Since 2008

Dengue virus type 3 (DENV-3) genotype III circulated across East Africa between 1984 and 1993, but no additional case was detected until the return of a European traveler from Cameroon in 2006. Since then, DENV-3 genotype III has been reported in many countries like Tanzania, Senegal and Cote d’Ivoire. Fifteen strains of DENV-3 were isolated from Africa by the laboratory of French National Reference Center for arboviruses between 2008 and 2012. The objective of the present study was to establish the phylogeny of new strains of DENV-3 genotype III isolated in Africa to better understand their origin(s) and diversity. Analyses showed that the Cote d’Ivoire 2008 strain was phylogenetically linked with the strains responsible for all the epidemics that occurred since then in West Africa including Cape Verde. This strain was also phylogenetically linked with the strain isolated in China in 2009. The Tanzanian 2010 strains cluster included the strains isolated in the Union of Comoros, Madagascar and China. Strains isolated from sporadic cases in La Reunion in 2012 clustered with the Thailand strain. These results evidenced the diversity of DENV-3 genotype III isolated in Africa between 2008 and 2012. The impact of air travel, tourism and trades should play a major role in the DENV spreading over continental Africa and African archipelagoes.