Spread of chikungunya from the Caribbean to mainland Central and South America: a greater risk of spillover in Europe?

Abstract

After a decade of outbreaks in Africa, the Indian Ocean and Asia, chikungunya virus (CHIKV) is stepping out of the shadow of dengue virus [1]. Although these two mosquito-borne viruses share clinical characteristics and their main vectors, Aedes albopictus (the tiger mosquito) and Ae. aegypti, CHIKV has long remained exotic to the western hemisphere [2]. The emergence of the Indian Ocean lineage changed the views on CHIKV when it caused an unprecedented disease burden in India and the islands of the Indian Ocean between 2005 and 2008 [3,4]. More than the reports of single events of locallyacquired cases of chikungunya fever in Italy and France [5,6], the recent occurrence of autochthonous transmission of CHIKV in the Americas has redesigned the geographic distribution of the virus. An outbreak in the Caribbean caused by an Asian strain of the virus started in Saint Martin in October 2013 with Ae. aegypti as the primary vector. The dynamics of the spread of CHIKV was in line with that in outbreaks that occurred in the Indian Ocean [2]. In this issue of Eurosurveillance, Cauchemez et al. estimate the basic reproductive number (the mean number of new host cases generated by one infectious host in a completely susceptible human population) at between 2 and 4 in the initial phase of the outbreak in the French Caribbean [7]. This is close to estimates from the outbreaks in Italy in 2007 and on Reunion Island in 2006 (3.5 and 3.7, respectively) [8,9]. Data from epidemiological surveillance suggest that so far, six months after its introduction to the Caribbean, CHIKV has been responsible for over 350,000 suspected cases of chikungunya fever that have occurred throughout the region [10].