The World Health Organization and other national health agencies are warning that the current Zika virus outbreak is likely to spread throughout nearly all the Americas. Alerts are being issued warning of the Aedes aegypti mosquito, carrier of the Zika virus which might cause microcephaly and Guillain-Barré syndrome, a condition that causes the immune system to attack one’s own nerves. Last year, there was a sharp increase in the number of babies born with microcephaly, in parts of Brazil affected by the Zika virus (2,700 newborns affected in 2015, compared to fewer than 150 in 2014.) The condition results in an abnormally small head in newborns and is associated with various disorders including decreased brain development. Zika has now spread to every country in the Americas, except Chile and Canada—with at least a dozen cases in the United States confirmed by the CDC. While research is being done to verify the link between Zika and microcephaly, authorities in several countries have advised couples to avoid pregnancy for the time being.