Since the identification of the Zika in Brazil in early 2015, the Americas. An increase in the number of infants with microcephaly in Brazil was first noted in September 2015, after the recognition of Zika virus transmission in the country earlier in the year, this was followed by the recognition of a similar increase in French Polynesia after an outbreak there in 2013 and 2014. Despite accumulating evidence that supports the link between Zika virus infection and microcephaly, most experts have taken care not to state that zika virus infection is causally related to these adverse outcomes.' This cautious approach toward ascribing Zika virus as a cause of birth defects is not surprising, given that the last time an infectious pathogen (rubella virus) caused an epidemic of congenital defects was more than 50 years ago, no flavivirus has ever been shown definitively to cause birth defects in humans, and no reports of adverse pregnancy or birth outcomes were noted during previous outbreaks of Zika virus disease in the Pacific Islands. on the basis of the available evidence, the public health response to the outbreak of Zika virus disease has moved forward, with the distribution of health messages about the importance