Chikungunya virus (CHIKV) is an Arbovirus belonging to Alphavirus genus, which is transmitted by Aedes spp mosquitoes. Since late 2004, CHIKV caused several outbreaks in coastal Kenya, in Indian Ocean (especially on island of La Reunion), and on Indian subcontinent, where it caused more than 1.5 million cases. Although Aedes aegypti is most commonly involved vector, other Aedes spp mosquitoes, such as Aedes albopictus, appear to have a good vectorial capacity for CHIKV. The vectorial capacity of Aedes albopictus is of special concern, since this mosquito is widespread in several countries in Southern Europe and in other areas of world, outside tropical areas. In summer of 2007, an unexpected outbreak of CHIKV fever, caused more than 200 human cases in Emilia-Romagna Region of Italy; most of cases were recorded in two villages in Province of Ravenna, but smaller clusters were also detected in other towns in same Region (i.e., towns of Cervia, Cesena, Ravenna, Rimini, and Bologna). The tropical virus was introduced in Italy by a man from Kerala (an Indian district affected by a large outbreak) and sustained by local mosquitoes (Aedes albopictus, the tiger mosquito), which transmitted infection to other persons. The epidemic can be said to have been result of globalisation of vectors and humans, which occurred through a two-step process: i) introduction and adaptation of Aedes albopictus to a new environment (i.e., an area with a temperate climate); and ii) introduction of Chikungunya virus (CHIKV) in a previously infection-free country, as a result of population movement. The CHIKV strains introduced in Italy contained a mutation in E1 glycoprotein which was responsible for a single amino-acid substitution (A226V) able to increase infectivity of virus for Aedes albopictus. CHIKV outbreaks did not reoccur in areas that had been affected by 2007 outbreak. This was probably consequence of three combined factors: i) lack of human cases during winter season, due to extremely reduced Ae. albopictus activity; ii) mosquito control activities performed during and after outbreak; and iii) extremely low rate of transovarial transmission of infection (i.e., transmission from adult mosquito to larvae). By contrast, on island of La Reunion, although number of human cases decreased during dry season, they did not completely disappear, and a second epidemic wave ravaged local population determining significant increase in mortality. Investigations conducted during recent outbreaks provided a unique opportunity to improve our knowledge on epidemiological, clinical and virological aspects of CHIKV infection (i.e., estimate of CHIKV infection R0, definition of clinical spectrum of disease, duration of viremia, antibody dynamics), and on evolutionary changes leading to virus adaptation to different vectors. In conclusion, re-emergence of CHIKV is paradigmatic of infectious threat in era of globalisation and emphasises need for preparedness and response to vector-borne infections and other emerging infectious threats.