Diagnosis of dengue fever in North West Italy in travelers from endemic areas: a retrospective study.

BACKGROUND: Domestic outbreaks of Dengue (DENV) fever from imported cases have to be considered a possible risk in non-endemic countries where Dengue vectors are present, such as in Italy.

OBJECTIVE: To review imported acute/recent DENV infections in a one-year survey in a North West Italy region where the presence of Aedes albopictus is documented.

STUDY DESIGN: We retrospectively reviewed laboratory and clinical records of Italian febrile travelers from Dengue endemic areas referring to the local reference Centre for Infectious Disease, covering a population of about 4 million people.

RESULTS: Acute/recent DENV infection was identified in 15 out of 91 travelers from endemic areas (16.5%) including 12 primary and 3 secondary infections; in 6 patients the virus was detectable in blood according to molecular real-time Polymerase Chain Reaction-based assays: in 9 patients the diagnosis of DENV infection was accomplished by the combination of specific IgM reactivity, high IgG titers, IgG seroconversion from negative to positive and increasing (four-fold) IgG titers in paired serum samples. Two cases of DENV infections were imported from South Egypt in patients travelling together, confirming the importance of returning travelers as sentinels of a rapidly changing epidemiology in specific geographic areas.

CONCLUSIONS: Our findings outline the high rate of imported Dengue infection in North West Italy and emphasize the need for a continued Dengue surveillance in non-endemic countries as well as a careful evaluation and follow-up of febrile patients returning from Dengue endemic countries.