Abstract
BackgroundChikungunya is an arthropod-borne viral disease now identified in over 60 countries in Asia, Africa, Europe, and the Americas. Chikungunya virus (CHIKV) has spread in the last 15 years to many countries, causing large local outbreaks. CHIKV infection can be clinically misdiagnosed in areas where dengue and/or Zika infections occur. Prospective studies are necessary to calculate the true incidence rate of CHIKV infection in travellers. The aim of this study was to obtain the attack and incidence rates of CHIKV infection among long-term travellers and identify associated risk factors.MethodsA previously collected prospective cohort of Dutch long-term travellers (12–52 weeks) to subtropical and tropical countries was tested. From December 2008 to September 2011, participants were recruited at the travel clinic of the Public Health Service Amsterdam. A weekly diary was kept during travel in which participants recorded their itinerary, symptoms, and physician visits. On return, their pre- and post-travel blood samples were tested for the presence of IgG antibodies to CHIKV antigen. Seroconversions were confirmed by an in-house CHIKV neutralisation test.ResultsThe median age of 603 participants was 25 years (interquartile range [IQR]: 23–29); 35.7% were male; median travel duration was 20 weeks (IQR: 15–25), and purpose of travel was predominantly tourism (62%).The presence of anti-CHIKV IgG in the pre-travel sample, suggestive of previous CHIKV infection, was found for 3/603 participants (0.5%); all three had been previously travelling in either Africa or Asia. In one traveler who visited Latin America, a seroconversion was found (0.2%) but the CHIKV neutralisation test was negative, making the incidence rate 0.ConclusionNo chikungunya virus infections were found in this 2008–2011 prospective cohort of long-term travellers. We recommend the research be repeated, particularly as the sample size of our cohort might have been too small. Also, extensive spread of chikungunya virus has likely increased incidence rates among travellers since 2013.
Highlights
Chikungunya is an arthropod-borne viral disease identified in over 60 countries in Asia, Africa, Europe, and the Americas
Laboratory methods After all study participants had returned, all post-travel serum samples were tested for immunoglobulin (Ig) G antibodies to Chikungunya virus (CHIKV) antigen by using an anti-CHIKV enzyme-linked immonosorbent assay (ELISA) Immunoglobulin G (IgG) test (Euroimmun, Lübeck, Germany), according to manufacturer’s instructions
Characteristics of the study population The prospective cohort consisted of 603 participants which formed the study population
Summary
Chikungunya is an arthropod-borne viral disease identified in over 60 countries in Asia, Africa, Europe, and the Americas. Prospective studies are necessary to calculate the true incidence rate of CHIKV infection in travellers. The aim of this study was to obtain the attack and incidence rates of CHIKV infection among long-term travellers and identify associated risk factors. Our primary aim was to estimate the attack rate and incidence rate of CHIKV infections during travel in Africa and Asia and to identify the associated risk factors. As we were curious as to possible exposure in countries with no evidence of autochthonous CHIKV transmission at the time of our study, we tested samples of all cohort travellers to Latin America [15, 16]
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