From last January, when the U.S. Centers for Disease Prevention and Control issued its first warnings to pregnant women on travel to Zika-endemic areas, to July when the agency for the first time warned against travel to a destination within the continental United States, to mid-December, when the number of Zika-prompted travel warnings at home and abroad totaled 60, the threat posed by the virus grew steadily throughout 2016. At the same time, so did knowledge of the dangers posed by the disease, which is both vector-borne and sexually transmitted, and is now confirmed to cause devastating neurologic birth defects and the paralyzing Guillain Barre syndrome.