Imported dengue fever: a 16-years retrospective analysis in Milan (Italy) and a brief review of the European literature

Dengue Fever (DF), transmitted by Aedes mosquitoes, is the most common arthropod-borne infection, it is almost ubiquitous in tropical and subtropical areas with an estimate of 360 million infections per year. A competent vector (A. albopictus) is present in most of Southern Europe and is endemic in Italy. We conducted a 16-year retrospective study of probable/confirmed dengue fever observed at the Department of Infectious Diseases of Luigi Sacco Hospital in Milan, Italy. Overall 122 patients were included in the study, 106 with probable and 16 with proven diagnosis of dengue fever. Most patients (91%) were Italian, with a median age of 35 years (IQR 29-46 years) and similar gender distribution, travelling for tourism (80%). Asia (mainly South East Asia and Indian Subcontinent) was the most frequent travel destination (55%), followed by Central America and the Caribbeans (22%). August-September was the peak season of presentation (42.6%). The majority of our diagnoses were based on serology alone. The most common signs and symptoms were fever (99,2%), maculopapular rash (50,8%), headache (50,8%), arthralgias (50,8%) and myalgias (46,7%). Leukopenia (77%), thrombocytopenia (81%) and altered LDH, AST and ALT (respectively 60,6%, 54,1% and 45,9%) were the most common laboratory test's abnormalities. No cases of severe DF were recorded. Our epidemiological and clinical findings are largely in accordance with most recent studies about imported DF in Europe. Although very similar in presentation to other arthropod-borne illnesses, some clinical features may help in differentiating DF from other causes of fever in the returning traveler.