Via Nature News & Comment, a report by Declan Butler: Brazil's surge in small-headed babies questioned by report. Excerpt:
Researchers at the body responsible for monitoring birth defects in Latin America are questioning the size of an apparent surge in the number of Brazilian children born with 'microcephaly' — abnormally small heads and brains.
Alarm is growing about a reported rise in suspected cases of the rare condition, which has been tentatively linked to the rapid spread of the Zika virus through the Americas. But Jorge Lopez-Camelo and Ieda Maria Orioli, from the Latin American Collaborative Study of Congenital Malformations (ECLAMC), say that the surge might largely be attributed to the intense search for cases of the birth defect, and misdiagnoses, because of heightened awareness in the wake of the possible link with Zika.
This ‘awareness’ effect is well known and inevitable, they say, and must be revealing cases that would have gone unnoticed under normal circumstances. They also say that a high rate of misdiagnoses among reported cases is likely because the diagnostic criteria being used for microcephaly are broad.
Lopez-Camelo and Orioli have summarized their analysis in a report, which they have newly translated into English and passed to Nature (ECLAMC Report). They say that from the epidemiological data available, it is impossible to establish the true size of the surge in microcephaly, and whether there is any link with the Zika virus.
In particular, large 'prospective' studies, in which pregnant women in areas of Brazil experiencing Zika outbreaks are monitored to see how many of their children develop microcephaly are needed, they say. Several research groups in and outside Brazil are already planning such studies, and some have begun.
Specialists contacted by Nature emphasize that it is prudent for pregnant women to be cautious — for example, by protecting themselves against mosquito bites — until more is known.
The experts agree that the reported size of the microcephaly increase so far is probably inflated — and this chimes with the latest figures from the Brazilian government. On 27 January, it said that of 4,180 suspected cases of microcephaly recorded since October, it has so far confirmed 270 and rejected 462 as false diagnoses.
But some disagree with the ECLAMC team's conclusion that the reported surge in recent months can mostly be attributed to an increase in the intensity of the search for cases and misdiagnosis. Thomas Jaenisch, a tropical medicine specialist at the Heidelberg University Hospital in Germany, calls this an “extreme” position and says that it “might also create uncertainty in the media and public discussion in Brazil”.
