BackgroundEmerging arboviruses such as chikungunya and Zika viruses have unexpectedly caused widespread outbreaks in tropical and subtropical regions recently. Ross River virus (RRV) is endemic in Australia and has epidemic potential. In Malaysia,Aedesmosquitoes are abundant and drive dengue and chikungunya outbreaks. We assessed risk of an RRV outbreak in Kuala Lumpur, Malaysia by determining vector competence of localAedesmosquitoes and local seroprevalence as a proxy of human population susceptibility.Methodology/Principal findingsWe assessed oral susceptibility of MalaysianAe.aegyptiandAe.albopictusby real-time PCR to an Australian RRV strain SW2089. Replication kinetics in midgut, head and saliva were determined at 3 and 10 days post-infection (dpi). With a 3 log10PFU/ml blood meal, infection rate was higher inAe.albopictus(60%) thanAe.aegypti(15%; p<0.05). Despite similar infection rates at 5 and 7 log10PFU/ml blood meals,Ae.albopictushad significantly higher viral loads and required a significantly lower median oral infectious dose (2.7 log10PFU/ml) thanAe.aegypti(4.2 log10PFU/ml).Ae.albopictusshowed higher vector competence, with higher viral loads in heads and saliva, and higher transmission rate (RRV present in saliva) of 100% at 10 dpi, thanAe.aegypti(41%).Ae.aegyptidemonstrated greater barriers at either midgut escape or salivary gland infection, and salivary gland escape. We then assessed seropositivity against RRV among 240 Kuala Lumpur inpatients using plaque reduction neutralization, and found a low rate of 0.8%.Conclusions/SignificanceBothAe.aegyptiandAe.albopictusare susceptible to RRV, butAe.albopictusdisplays greater vector competence. Extensive travel links with Australia, abundantAedesvectors, and low population immunity places Kuala Lumpur, Malaysia at risk of an imported RRV outbreak. Surveillance and increased diagnostic awareness and capacity are imperative to prevent establishment of new arboviruses in Malaysia.