With the proposed connection between the Zika virus and Brazil's outbreak of microcephaly in new born babies looking increasingly tenuous, Latin American doctors are proposing another possible cause: Pyriproxyfen, a pesticide used in Brazil since 2014 to arrest the development of mosquito larvae in drinking water tanks.
Might the 'cure' in fact be the poison?
Malformations detected in thousands of children from pregnant women living in areas where the Brazilian state added Pyriproxyfen to drinking water are not a coincidence, even though the Ministry of Health places direct blame on the Zika virus.
The World Health Organization view that the microcephaly outbreak in Brazil's impoverished northeast is caused by the Zika virus has, so far, received few challenges.
Brazil's Health Minister, Marcelo Castro, has gone so far as to say that he has "100% certainty" that there is a link between Zika and microcephaly, a birth defect in which babies are born with small heads.
The view is widely supported in the medical community worldwide, including by the US's influential Center for Disease Control. But there is no hard evidence of the link, rather a mixture of epidemiological indications and circumstantial evidence.
One of the key scientific papers, by A S Oliveira Melo et al in the journal Ultrasound in Obstetrics & Gynecology, found Zika virus in the amniotic fluids and other tissues of the affected babies and their mothers. But only two women were examined, far too small a number to establish a statistically significant link.
The New York Times also reported on 3rd February on the outcome of analyses by Brazil's Health Ministry: "Of the cases examined so far, 404 have been confirmed as having microcephaly. Only 17 of them tested positive for the Zika virus. But the government and many researchers say that number may be largely irrelevant, because their tests would find the presence of the virus in only a tiny percentage of cases."
And last weekend, the most powerful indicator yet that the microcephaly may have another cause altogether was announced by Colombia's president, Juan Manuel Santos, as reported by the Washington Post. Colombian public health officials, stated Santos, have so far diagnosed 3,177 pregnant women with the Zika virus- but in no case had microcephaly been observed in the foetus.
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