— Often drowned out by the dire warnings and fear surrounding Zika, some medical professionals are saying that Brazil and international health officials have prematurely declared a link between the virus and what appears to be a surge in birth defects.

A few even argue that the Brazilian government is being irresponsible, given that a connection hasn’t been scientifically proven between the mosquito-borne virus and the birth defect known as microcephaly, which causes infants to be born with abnormally small heads.

“It’s a global scandal. Brazil has created a worldwide panic,” said Alexandre Dias Porto Chiavegatto Filho, a professor of epidemiology at the University of Sao Paulo, one of the most-respected universities in Latin America. “I’m not saying that Zika is not causing microcephaly, but I am saying that the ministry has yet to present any scientifically credible evidence to support that conclusion.”

Chiavegatto and others argue there are still too many unanswered questions to blame Zika. Why are the vast majority of the cases of microcephaly being reported in Brazil? Why haven’t they also shown up in proportional numbers in other countries hit hard by Zika, such as Colombia? (The answer, some say, is that Brazil was hit by Zika first, and microcephaly cases might be expected to crest elsewhere in the months ahead.)

In an article published Wednesday by the Annals of Internal Medicine, 14 Brazilian and American researchers said the link between Zika and microcephaly “remains presumptive.” The strongest evidence is circumstantial, they said, and there are challenges in confirming the connection.

But Brazilian Health Minister Marcelo Castro recently said he was “absolutely sure” of a causal link between Zika and microcephaly. He and other scientific experts around the world have pointed to studies that detected the presence of Zika in the brains of dead fetuses and in the placentas of babies diagnosed with microcephaly in the womb.

While visiting Brazil on Wednesday, Margaret Chan, director-general of the World Health Organization, said microcephaly can be caused by many things but that her organization was affirming that “Zika is responsible (for it in Brazil) until evidence to the contrary emerges.” And the Atlanta-based Centers for Disease Control and Prevention has warned pregnant women against traveling to more than 30 destinations where the virus has been registered.

Still some critics are not satisfied.

Luis Correia, who teaches scientific method at the Bahia School of Medicine and Public Health, said the small-scale studies cited by health officials don’t equal proof. “There appears to be a sort of scientific illiteracy within the ministry that has led them to mix up association with causality.”


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