  Chikungunya fever (CHIKV), a viral disease transmitted by mosquitoes, is
currently affecting several territories in the Caribbean. The vector is found
in the Americas from South Florida to Brazil and the Caribbean is a highly
connected region. There is therefore a significant risk for the epidemic to
quickly expand to a wide area in the Americas, and of introduction to Europe
where competent vectors are present. Here, we describe the spread of CHIKV in
the first three territories to report cases and between territories of the
region. Local transmission of CHIKV in the Caribbean is found to be very
effective (mean number of cases generated by a human case in the range 2 to 4).
There is a strong spatial signature in the regional epidemic, with the risk of
transmission between territories estimated to be inversely proportional to the
distance rather than being driven by air transportation. So far, this simple
model has successfully predicted observed patterns of spread. The spatial
structure allows ranking territories according to their current risk of
invasion. This characterization may help national and international agencies to
optimize resource allocation for monitoring and control and encourage
territories with elevated risks to act. This is important to reduce the risk of
dissemination to other parts of the world, including Europe.
