Dengue virus transmission is ubiquitous throughout the tropics, in countries where the mosquito vectors – predominantly Aedes aegypti and Aedes albopictus – are present. Over 70% of the estimated 390 million annual global infections occur in the Southeast Asian and Western Pacific region. All four dengue virus (DENV) serotypes circulate in this region and many countries have recorded hyperendemic transmission (defined as co-circulation of multiple DENV serotypes). Secondary infection with heterologous DENV is associated with worse clinical outcome, and infection with certain genotypes is associated with more, or less, severe dengue disease. DENV serotype and genotype data is lacking in many parts of the region, limiting our attempts to understand the observed patterns of hyperendemicity, epidemic virulence, and disease severity. Many countries in the region are popular tourist destinations, and dengue has been identified as a cause of travel-related illness. We have established the WA Traveller’s Cohort whereby returned travellers (predominantly from Bali, Indonesia) with well-defined flavivirus infection are recruited. Peripheral blood mononuclear cells, serum and plasma obtained in acute phase illness and in convalescence are cryopreserved, and used in our ongoing phylogenetic and immunologic analyses.
Surveillance of symptomatic returned travellers provides important and timely information on regional mosquito-borne flavivirus infections and allows detailed analysis of currently circulating DENV, and more recently, Zika virus, strains and immunity; an overview of the Cohort and data generated to date will be presented.