Autochthonous dengue virus infection in Japan imported into Germany, September 2013

Abstract

In September 2013, dengue virus (DENV) infection was diagnosed in a German traveller returning from Japan. DENV-specific IgM and IgG and DENV NS1 antigen were detected in the patient's blood, as were DENV serotype 2-specific antibodies. Public health authorities should be aware that autochthonous transmission of this emerging virus may occur in Japan. Our findings also highlight the importance of taking a full travel history, even from travellers not returning from tropical countries, to assess potential infection risks of patients.Here we report the clinical and laboratory findings of a dengue virus (DENV) infection acquired in Japan in late summer 2013 and imported into Germany. Airport to Tokyo Narita International Airport and came back the same way. The patient was vaccinated against yellow fever in 2009, because she had travelled to Kenya that year. In the beginning of 2012, she travelled to Singapore. Among several other diseases, dengue fever was suspected, because of the clinical picture.The first serum sample, collected seven days after symptom onset, gave a positive result in DENV IgM and IgG antibody tests (in-house indirect immunofluorescence assay (IIFA), according to [1-3]), as well as for DENV nonstructural protein-1 (NS1) antigen tested by ELISA (Bio-Rad Platelia Dengue NS1 Ag) and a rapid test (SD BIOLINE Dengue Duo NS1 Ag + Ab Combo), demonstrating an acute DENV infection (Table). Realtime RT-PCR for DENV RNA [4] and generic flavivirus RT-PCR [5] were negative.The thrombocytopenia resolved without complications and after one week in hospital, the patient was discharged with a characterisation of restitutio ad integrum (restoration to original condition). A follow-up serum sample was collected in December 2013, 110 days after symptom onset, because this acute case of dengue fever imported from Japan was considered very unusual. This second serum sample revealed a significant decrease in DENV IgG titre in the IIFA and negative results for DENV NS1 antigen (ELISA and rapid test) and DENV IgM (IIFA and rapid test) (Table). In order to identify the causative DENV serotype, an immune complex binding ELISA [6] was performed on the second serum sample, demonstrating the presence of DENV serotype 2-specific antibodies ( Table) and the absence of DENV serotype 1-, 3-and 4-specific antibodies, thus excluding a secondary DENV infection. BackgroundDENV is an arthropod-borne RNA virus of the Flaviviridae family causing dengue fever in humans. Aedes aegypti 2 www.eurosurveillance.org (Linnaeus) and Ae. albopictus (Skuse) mosquitoes are considered to be the main vectors of DENV worldwide [7]. DENV has emerged in recent decades as a worldwide public health problem: current estimations assume 390 million DENV infections per year, with 96 million clinically apparent cases [7]. The virus is found in tropical and subtropical regions around the world, with hyper-endemic areas in Central and South America and in south-east Asia. It is considered an emerging threat to Europe because of its detection in Croatia (

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“…A. albopictus is present in Japan, and in August 2012, invasion of the yellow fever mosquito, A. aegypti, was reported at Narita International Airport (3) and then at Haneda International Airport in early to mid-2013 (personal communication). Moreover, in late August 2013, a single DENV infection was confirmed in a German individual travelling to Japan (4,5). In this study, we demonstrated the susceptibility of foreign (imported) and Japanese (indigenous) Aedes mosquito spp.…”