WIKIMEDIA, NASAIn the past year, clinicians in Brazil have reported around 4,700 babies with suspected microcephaly, and reviews of 400 of the infants have confirmed the birth defect (another 700 suspected instances of microcephaly have been ruled out). The numbers are alarming to many clinicians in the South American nation. Some have questioned whether the cause of this increase in microcephaly is due to Zika virus—a hypothesis favored by many doctors and public health officials—other infections, or simply a catch-up in reporting.
To get a grasp on just how much the prevalence of microcephaly has changed recently, Sandra da Silva Mattos of the Círculo do Coração de Pernambuco and colleagues combed through the medical records of more than 16,000 babies. The infants were born between 2012 and 2015 at one of 21 medical centers in the state of Paraíba, which has been hard hit by Zika.
Since 2012, Mattos’s team found, a strikingly large number of babies—4 percent to 8 percent—appeared to have microcephaly, according to the broadest definitions of the term. Additionally, the number of babies affected peaked in 2014, before Zika had been detected in Brazil.
“What we expected was that we would have something like three to four cases a year of microcephaly—that is ...
