We next estimated the maximum number of births potentially affected by ZIKV in Latin America, as this region is the focus of the recent outbreak and the first to point to a possible
association with microcephaly in newborn infants to mothers infected with ZIKV.
An
association between Zika infections during pregnancy and the birth of babies
with microcephaly (a birth defect in which an infant's brain does not develop properly resulting in a smaller than normal head) was first suggested by Brazilian physicians in August 2015, and in November
microcephaly cases potentially associated
with Zika started to be recorded; three months later WHO made its announcement.
The included birth defects were based primarily on case reports of outcomes occurring in
association with Zika virus infection during pregnancy; there is more evidence for some of these birth defects than for others, and a causal link has not been established for all.5,10,12,21 - 27 Because much of the focus to date has been on
microcephaly and brain abnormalities, data were summarized in 2 mutually exclusive categories: (1) brain abnormalities
with or without
microcephaly regardless of the presence of additional birth defects and (2) neural tube defects and other early brain malformations, eye abnormalities, and other consequences of central nervous system dysfunction among those without evident brain abnormalities or
microcephaly.