ZIeKA monitor study: travel-related arbovirus infections among Dutch travellers, 2018–2020

This study aims to estimate the incidence of arbovirus infections among Dutch travellers and subsequent potential risk of importation. For this prospective, fully remote study, Dutch travellers visiting arbovirus endemic countries between August 2018 to March 2020 were recruited through (social) media and travel-clinics. Interested travellers could register online. Participants completed questionnaires and kept a daily symptom log during travel using a custom-made study app. Travellers reporting symptoms suggestive of arbovirus infection were invited to self-collect a dry-blood spot sample (DBS) upon return. In a sub-cohort of participants, post-travel DBS were also collected if asymptomatic. Participants mailed the DBS to the laboratory to be tested by PCR for ZIKV, DENV and CHIKV, along with IgG and IgM antibody testing. Of 1222 subjects registering online, 737 (60.3 %) completed the baseline questionnaire and ≥60 % of symptom diaries and were included in the analysis. Arbovirus-like symptoms were reported by 73 participants (9.9 %). A post-travel DBS was obtained from 67 symptomatic and 154 asymptomatic travellers. None were RT-PCR positive for ZIKV, DENV or CHIKV. Two symptomatic travellers were IgM positive indicating probable recent arbovirus infection. An additional ten cases were IgG positive/IgM negative suggesting possible previous arbovirus exposure. The estimated incidence proportion and rate of travel-related arbovirus infection were 2.7–16.3/1000 trips and 3.9–23.4/1000 person-months, respectively. While a small proportion of travellers to arbovirus endemic areas have evidence of recent infection, the risk of arbovirus importation by returning travellers appears low as viraemia was not detected in any participant upon return.