Seroprevalence of Dengue Virus, West Nile Virus, Chikungunya Virus, and Zika Virus in International Travelers Attending a Travel and Migration Center in 2015-2017, Southern Italy

International travelers to areas endemic for vector-borne diseases (VBDs) may be at risk of contracting and spreading these diseases. The aim of this study was to evaluate the prevalence of immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies that are specific for Dengue Virus (DV), West Nile Virus (WNV), Chikungunya Virus (CHIKV), or Zika Virus (ZV) in a cohort of international travelers. The study enrolled travelers who attended the Travel Medicine and Migration outpatient service of Local Health Unit of Bari, Italy, in March 2015-June 2017 for counseling and vaccine prophylaxis before travel. After receiving informed consent, post-travel blood samples were tested for IgM and IgG antibodies specific for DV, WNV, CHIKV, and ZV. Of the 207 travelers attending the vaccine service, 156 (75%) were enrolled. Of the 156 subjects, 23 (14.7%) had IgM and/or IgG antibodies specific for at least one VBD. Of these, 12 (52%) were asymptomatic. Nineteen (12.2% of the whole cohort), nine (5.8%), nine (5.8%), and two (1.3%) subjects had IgM and/or IgG antibodies specific for DV, WNV, CHIKV, and ZV, respectively. Ten subjects (6.4%) harbored antibodies that were specific for more than one VBD. A significant number of the international travelers were DV-positive. Our findings suggest that international travelers should undergo serological surveillance, particularly those who travel frequently and for long periods to areas that are endemic for hemorrhagic dengue. Due to a possible risk of introducing VBDs into nonendemic areas, increased awareness among physicians and travelers and appropriate laboratory detection are crucial. There are currently no licensed vaccines for these VBDs in Italy or other European countries; the main preventive measures are protection from mosquito bites and vector control.