Isolation of DENV2-PR159 derived viral escape mutant EM41 and of DENV2-QR94 derived EM33. One week post-emergence, females of the laboratory adapted Higgs White Eye (HWE) strain received artificial bloodmeals containing ~107 pfu/ml DENV2-QR94 (American genotype DENV2 from Quintana Roo, Mexico) or DENV2-PR159 (American genotype DENV2 from Puerto-Rico). Viruses had been propagated for 12–14 days in C6/36 cells. Artificial bloodmeals consisted of infected C6/36 cell culture supernatants mixed at a 1:1 ratio with defibrinated sheep blood. Mosquitoes were allowed to feed for 1 h. Virus titers of individual miguts were assayed by plaque assays in LLC-MK2 (monkey kidney) cells at 7 days post-bloodmeal. Bars in the diagram represent mean values. Numbers of tested individuals to identify EM41 and EM33 were 121 and 31, respectively.