Zika virus outbreak in Cabo Verde Islands, West Africa: early epidemiological findings

The Zika virus (ZIKV) outbreak in the island nation of Cabo Verde was of unprecedented magnitude in Africa and the first to be associated with microcephaly in the continent. Here we present its first epidemiological assessment by investigating attack and observation rates from 7,580 ZIKV notified cases and 18 microcephaly reports between July 2015 to May 2016. The basic reproductive number of the outbreak in Cabo Verde was estimated around 1.66 (95% confidence interval, CI, 1.39-1.98), similar to that reported in the Americas. Assuming that the microcephaly risk per pregnancy is identical between Cabo Verde and the Americas we extrapolate that ~56% (CI: 47 to 65)% of the population may have been infected with ZIKV. Our results highlight the need for rapid and integrated epidemiological, molecular and genomic arbovirus surveillance to tackle forthcoming outbreaks in Cabo Verde and other African nations.