Estimated imported infections of Chikungunya and Dengue in Italy, 2008 to 2011.

BACKGROUND: In temperate countries, where the competent vector is present, the risk of introduction and transmission of Chikungunya (CHIKV) and Dengue (DENV) cases is particularly high. Thus, epidemiological surveillance is crucial to rapidly identify imported cases in order to introduce measures to reduce mosquito density in the area.

METHODS: We analyze imported cases of CHIKV and DENV reported to the National Institute of Health (ISS) and the Ministry of Health, from January 2008 through October 2011 within the National Surveillance system in Italy. Moreover, considering the worldwide spread of DENV and CHIKV and the consequent importation of cases in Italy we estimate the number of imported cases using data on airport arrivals of travelers to the Italian international airports.

RESULTS: From January 2008 to October 2011 a total of 130 cases of DENV/CHIKV were reported in travelers returning to Italy. In our study, 42.8% of CHIKV cases were imported from Indian Ocean Islands (Mauritius, Maldives, Bali, and Sri Lanka), whereas, for DENV 40.4% of imported cases reported to have visited Asia within the incubation period. The estimated number of exposed travelers to CHIKV and DENV arriving in Italy was higher compared to notified cases, suggesting a possible underestimation of the real number of imported cases.

CONCLUSIONS: Integrated human and entomological surveillance is crucial to monitor the spread of emerging vector-borne diseases and to implement public health measures in order to avoid transmission and control such diseases in humans.