In the fall and early winter of 2015, a startling number of infants in northeastern Brazil were born with abnormally small heads. Mounting global concern gave rise to theories about what was responsible. And while public health authorities fairly quickly fingered the Zika virus as the culprit, a couple of other theories established deep roots on social media platforms.
But the just-published final report of a study conducted in Brazil discounts those two theories. The work, by Brazilian scientists, suggested there is no link between the cases of microcephaly and exposure to the insecticide pyriproxyfen, nor to maternal vaccination during pregnancy.
[Researchers] compared the pregnancies of women who gave birth to babies with microcephaly to women who gave birth at the same time to babies without the condition. The case-control study gathered reams of information about the gestation of the cases — 82 babies and nine affected fetuses that were stillborn — and those of 173 healthy babies that served as the “controls.”
[T]he biological plausibility of these two rumored causes was always weak. By contrast, the association between Zika infection during pregnancy and microcephaly was “extremely strong,” the study authors reported. The study also found that a high proportion of the mothers of the control babies had antibodies to Zika virus, illustrating how widespread infection was in northeastern Brazil.
Read full, original post: Zika virus, not vaccine or insecticide, linked to birth defects in Brazil