Aim: The objective of this study is to present epidemiological characteristics and clinical symptoms of dengue fever cases in Czech workers who acquired the infection while working on the island of Fushivelavaru, Maldives. Furthermore, the study compares the sensitivity of novel direct detection assays, i.e. Real-Time Polymerase Chain Reaction (RT-PCR) and detection of Dengue NS1 antigen.
Material and methods: The retrospective study evaluated the clinical course of dengue fever cases in Czech workers returning from a job in the Maldives who were diagnosed with dengue virus infection from September 1 to October 31, 2012. The laboratory diagnosis of dengue fever was based on the serological detection of IgM and IgG antibodies, detection of dengue NS1 antigen by enzyme-linked immunosobent assay (ELISA), and detection of dengue virus DNA by RT-PCR.
Results: The infection with dengue virus was confirmed in 18 males with a median age of 40 years (IQR 36-47) who returned from a job in the Maldives. Only one patient required admission to the hospital while the others were treated on an outpatient basis. The most frequently observed symptoms were fever (18), headache (9), muscle and joint pain (8 and 7, respectively), and rash (9). Typical laboratory findings were leukocytopenia and thrombocytopenia, a low CRP level, and elevated aminotransferase activity. The clinical course was uncomplicated in all patients. The dengue NS1 antigen detection (positive in all 10 patients with acute dengue fever) showed significantly higher sensitivity than the detection of viral RNA using RT-PCR (positive in 4 patients), p = 0.011.
Conclusion: Although the vast majority of dengue fever cases are diagnosed among travellers returning from the tropics, the presented study points out the risks posed by dengue fever to long-term workers in endemic areas. The infection in the serologically naïve hosts is usually uncomplicated; however, infected persons are at significant risk of developing a severe complicated clinical course if challenged by another serotype. Furthermore, sick leaves or premature departures cause a considerable economic burden to employers. In the diagnosis of acute dengue fever, preference should be given to highly sensitive and specific tests for the direct detection of dengue virus (NS1 antigen and RT-PCR assays).