Unknowns about Zika virus continue to frustrate
Public health officials race to find answers, develop a vaccine
![zika](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2016/02/021216_mr_zikaupdate_free.jpg?fit=860%2C460&ssl=1)
GOING VIRAL Zika virus (shown in this false-color transmission electron micrograph) continues to spread across the Americas, and may be linked to a recent rise in birth defects in Brazil.
Jessica Wilson/Science Source