Rates of birth defects linked to Zika infection during pregnancy have increased in parts of the United States where local transmission of the virus has occurred, according to the CDC’s Morbidity and Mortality Weekly Report (MMWR). These areas include southern Florida, parts of southern Texas, and Puerto Rico.
In these areas of the country, rates of birth defects strongly associated with the Zika virus – microcephaly (small head size), other brain abnormalities, neural tube defects, eye abnormalities, joint problems, and deafness, for example – rose 21 percent in the last half of 2016 compared to the first half of the year. But the CDC says it isn’t clear if this increase can be attributed to local transmission of Zika alone, or if other factors contributed to the rise in birth defect rates.
Most mothers of infants born with Zika-linked birth defects did not have laboratory-confirmed evidence of infection because they were not tested for the virus, were not tested for the virus at the right time, or were not exposed to Zika. Birth defects that could be related to Zika infection are monitored by surveillance systems.