Incidence of disease due to dengue (DENV), chikungunya (CHIKV) and yellow fever 
(YFV) viruses is increasing in many parts of the world. The viruses are 
primarily transmitted by Aedes aegypti, a highly domesticated mosquito species 
that is notoriously difficult to control. When transinfected into Ae. aegypti, 
the intracellular bacterium Wolbachia has recently been shown to inhibit 
replication of DENVs, CHIKV, malaria parasites and filarial nematodes, providing 
a potentially powerful biocontrol strategy for human pathogens. Because the 
extent of pathogen reduction can be influenced by the strain of bacterium, we 
examined whether the wMel strain of Wolbachia influenced CHIKV and YFV infection 
in Ae. aegypti. Following exposure to viremic blood meals, CHIKV infection and 
dissemination rates were significantly reduced in mosquitoes with the wMel 
strain of Wolbachia compared to Wolbachia-uninfected controls. However, similar 
rates of infection and dissemination were observed in wMel infected and 
non-infected Ae. aegypti when intrathoracic inoculation was used to deliver 
virus. YFV infection, dissemination and replication were similar in 
wMel-infected and control mosquitoes following intrathoracic inoculations. In 
contrast, mosquitoes with the wMelPop strain of Wolbachia showed at least a 
10(4) times reduction in YFV RNA copies compared to controls. The extent of 
reduction in virus infection depended on Wolbachia strain, titer and strain of 
the virus, and mode of exposure. Although originally proposed for dengue 
biocontrol, our results indicate a Wolbachia-based strategy also holds 
considerable promise for YFV and CHIKV suppression.