Birth defects associated with Zika virus infection during pregnancy increased 21% in the last half of 2016 in Puerto Rico and portions of Florida and Texas where local Zika virus transmission have been reported, according to a report released today by the Centers for Disease Control and Prevention. It is not known if the increase is due to local transmission of the virus alone or other contributing factors. Most of the mothers did not have laboratory evidence of Zika infection, either because they were not tested or tested at the right time or were not exposed, CDC said. The authors looked at 2016 births in all or portions of Florida, Georgia, Hawaii, Iowa, Illinois, Massachusetts, New Jersey, New York North Carolina, Puerto Rico, Rhode Island, South Carolina, Texas, Utah, and Vermont. CDC anticipates there could be another increase in possible Zika-related birth defects when 2017 data are analyzed, because many pregnant women exposed to Zika virus in late 2016 gave birth in 2017.