Evidence of an association between neurological manifestations (microcephaly and GBS) and Zika virus infection: the usefulness of ecological studies with syndromic surveillance data

The first relevant clinical and epidemiological Zika outbreaks were described in 2007 in the Yap Islands (1) and six years later in French Polynesia, with an estimate of 29,000 cases occurring in the period from October 2013 to February 2014 (2). In late 2014, cases of acute exanthematous illness (AEI), involving widespread rash of unclear etiology, were reported in several municipalities in northeastern Brazil. The identification of Zika virus (ZIKV) occurred in May of the same year and subsequent expansion to other regions was observed. ZIKV infection has been reported in Rio de Janeiro since January 2015 (3).