<ns4:p><ns4:bold>Background</ns4:bold>. Outbreaks of mosquito-borne arboviral diseases including dengue virus (DENV), Zika virus (ZIKV), yellow fever virus (YFV) and chikungunya virus (CHIKV) have recently occurred in the Caribbean. The geographical range of the principle vectors responsible for transmission, <ns4:italic>Aedes (Ae.) aegypti</ns4:italic> and <ns4:italic>Ae</ns4:italic>.<ns4:italic> albopictus </ns4:italic>is increasing and greater mosquito surveillance is needed in the Caribbean given international tourism is so prominent. The island of Saint Lucia has seen outbreaks of DENV and CHIKV in the past five years but vector surveillance has been limited with the last studies dating back to the late 1970s. Natural disasters have changed the landscape of Saint Lucia and the island has gone through significant urbanisation.</ns4:p><ns4:p> <ns4:bold>Methods</ns4:bold>. In this study, we conducted an entomological survey of <ns4:italic>Ae. aegypti </ns4:italic>and <ns4:italic>Ae. albopictus</ns4:italic> distribution across the island and analysed environmental parameters associated with the presence of these species in addition to screening for medically important arboviruses and other flaviviruses.</ns4:p><ns4:p> <ns4:bold>Results.</ns4:bold> Although we collected <ns4:italic>Ae. aegypti</ns4:italic> across a range of sites across the island, no <ns4:italic>Ae. albopictus</ns4:italic> were collected despite traps being placed in diverse ecological settings. The number of <ns4:italic>Ae. aegypti</ns4:italic> collected was significantly associated with higher elevation, and semi-urban settings yielded female mosquito counts per trap-day that were five-fold lower than urban settings. Screening for arboviruses revealed a high prevalence of a novel insect-specific flavivirus closely related to cell fusing agent virus (CFAV).</ns4:p><ns4:p> <ns4:bold>Conclusions.</ns4:bold> Outbreaks of arboviruses transmitted by <ns4:italic>Ae. aegypti</ns4:italic> and <ns4:italic>Ae. albopictus</ns4:italic> have a history of occurring in small tropical islands and Saint Lucia is particularly vulnerable given the limited resources available to undertake vector control and manage outbreaks. Surveillance strategies can identify risk areas for predicting future outbreaks and further research is needed to determine the diversity of current mosquito species and this should be extended to the neighbouring smaller Caribbean islands.</ns4:p>