Via NEJM, two letters to the editor and a reply: Zika Virus. Excerpt:
Petersen et al. (April 21 issue) provide a detailed review of Zika virus. We have some concern regarding diagnostic criteria for microcephaly in fetuses and newborns exposed to the virus. According to the Centers for Disease Control and Prevention (CDC) recommendation that microcephaly should be defined as an occipitofrontal circumference below the third percentile, nearly 3% of newborns would be categorized as having microcephaly.
In Brazil, where there are 3 million live births per year, the application of this definition would result in nearly 90,000 infants being labeled as having microcephaly — a far greater number than any studies to date would indicate. The comparable number in the United States would not be 2 to 12 cases per 10,000 live births, as noted in the article, but rather 3% of 4 million live births, or 120,000 newborns.
The “benchmark” of an average of 6 cases per 10,000 live births in the United States is based on the most commonly used criterion of 3 SD from the mean, which would encompass 0.27% of newborns.
A comparison of prevalence with the use of such radically different criteria will lead to grossly inappropriate conclusions and hysteria among pregnant patients. Unfortunately, this error has been repeated in press releases and needs to be corrected.
