Detection of circulating mosquito-borne arboviruses in Brazil using travellers as sentinels

Travellers visiting countries endemic for arboviral diseases may introduce arboviruses to new areas where competent vectors are already present, potentially leading to disease outbreaks in populations that have not previously been exposed. To assess exposure risks for travellers and identify which arboviruses they might import, we explored the use of international travellers to collect mosquito saliva samples at their travel destinations to map locally circulating arboviruses. We recruited 73 travellers from Switzerland visiting Brazil between August 2018 and June 2019 and provided each of them with five kits to collect viral RNA on Flinders Technology Association cards. We have chosen Brazil as a study area for a proof of concept for reasons of convenience, as this is a popular travel destination. We asked the travellers to place the kits at their destinations and use a smartphone app to track their locations. We received 155 kits back and screened the cards for arboviral RNA using reverse transcriptase PCR with consecutive sequencing of amplicons from positive samples. Due to RNA degradation during an extended storage period, 129 cards produced no positive signal. In contrast, among 26 cards that could be processed shortly after receipt, seven were positive for dengue virus serotype 4 and three for West Nile virus lineage 2 (WNV-2). To our knowledge, this is the first time WNV-2 has been reported from Brazil. Our 'citizen science' approach has the potential to contribute to arbovirus surveillance, extending the geographic range of sampling - particularly in regions lacking an arbovirus surveillance programme.