By Dominic Wilkinson @Neonatalethics
Towards the end of last year, and over the first months of 2016, there were alarming reports of the explosive spread of Zika virus infection in South America. As many as 1.5m Brazilians were thought to have contracted the virus. More, worrying still, there were reports of thousands of cases of congenital microcephaly – infants born with abnormally small heads because of brain damage in the womb. Each week there appeared to be more reports and larger numbers of infants affected.
But the latest estimates from Brazil have reversed this trend. Last week, the total number of confirmed and suspected cases of Zika microcephaly is reported to be 4,759, 500 less than two months ago.
Why are the numbers of cases falling? Does this mean that earlier reports about Zika were wrong? Is the Zika panic over?
One possibility is that microcephaly previously was underdiagnosed in Brazil. Prior to 2015, there were around 200 cases reported per year in Brazil. However, this rate appears strikingly low. International studies suggest that microcephaly (in the absence of Zika virus) occurs in approximately six out of every 10,000 newborn infants. Based on Brazil’s birth rate of 2.9m babies per year, we would expect there to be 1,700 cases per year.
So part of the initial surge in cases may have been due to recognition of cases of microcephaly that weren’t necessarily related to Zika infection.
Did the intense attention on microcephaly lead to overdiagnosis?
The latest document from the Brazilian health ministry shows that 7,438 cases of microcephaly had been notified up to May 7.
The views, opinions and positions expressed by these authors and blogs are theirs and do not necessarily represent that of the Bioethics Research Library and Kennedy Institute of Ethics or Georgetown University.