Areas in which the mosquito-borne virus has been circulating, including Puerto Rico, southern Florida and part of south Texas, saw a 21 percent rise in birth defects strongly linked with Zika in the last half of 2016 compared with the first half of that year, the U.S.
states and Puerto Rico to look for birth defects possibly associated with Zika.
They divided these areas into three groups: places with local Zika transmission, places with higher levels of travel-associated Zika, and places with lower rates of travel-related Zika.
Overall, they found three cases of birth defects potentially related to Zika per 1,000 live births out of 1 million births in 2016, about the same as the prior reporting period in 2013-2014.
When they looked specifically in areas with local Zika transmission and looked only at birth defects most strongly linked with Zika, they saw an increase.