Anencephaly is a "uniformly fatal" birth defect that leaves babies born without part of their brain or skull—and it's been striking three counties in rural Washington state at a rate at least four times the national average. But the cluster—in Yakima, Franklin, and Benton counties—remains cloaked in mystery, with no single cause pinpointed. The state's health department and the CDC in July issued a report that cited 23 cases of anencephaly between January 2010 and January 2013. A genetic counselor has since seen eight or nine more cases of it and spina bifida, NBC News reports. Officials were first alerted by a 58-year-old nurse who had seen no more than two cases of anencephaly in her decades-long career—and then experienced two cases in a six-month span, and learned of a third.
Officials dug into the cases of the women involved, and found "no common exposures, conditions, or causes"—having reviewed everything from their education and BMI to their water supply to any medications they took, the Yakima Herald Republic noted at the time. But some are faulting officials for not actually alerting the women that they were part of a perceived cluster, or actually interviewing them. Doing so could reveal "common environmental exposures," says a Duke genetics professor who specializes in anencephaly; she notes that research has shown a correlation between the defect and mold and pesticide exposure, and that the Central Washington area is an agriculture-heavy one. The Seattle Times previously reported on other potential risk factors: A diet lacking in folic acid, a contaminant in cornmeal, and elevated nitrates levels in drinking water. Still, the CDC maintains it could just be a coincidence. A report on the number of cases recorded in 2013 is due this spring.