Public health officials have admitted that the Zika virus is "scarier" than first thought and its impact on the US could be greater than predicted.
Dr. Anne Schuchat of the US Centers for Disease Control and Prevention said that a wider range of birth defects has been linked to the virus.
And he added that the mosquitoes that carry the virus could travel to more US states than previously thought.
The current Zika outbreak began almost a year ago in Brazil.
It has been linked to thousands of birth defects in the Americas.