Two new studies provide “frightening and sobering” evidence that the Zika virus may be causing not just microcephaly but other negative outcomes during all stages of pregnancy, from fetal death to potential blindness caused by damage to the central nervous system.

The papers, published by the New England Journal of Medicineand Cell Stem Cell, were both published online Friday, hours after the World Health Organization announced an emergency committee meeting next week to review “accumulating evidence” linking Zika with serious neurological disorders.

It will be the second such meeting since the WHO first declared a public health emergency over Zika’s worrying link to the autoimmune disorder Guillain-Barré syndrome and microcephaly, a birth defect associated with abnormally small brains and developmental delays.

Zika’s culpability has yet to be definitively proven —proof is probably months or years away — but these latest studies lend further support to the WHO’s position that Zika is “guilty until proven innocent.”

“The evidence has now become very compelling and I think it’s urgent to continue to study this very aggressively,” said Dr. Mark Schleiss, director of pediatric infectious diseases and immunology at the University of Minnesota Medical School, who was not involved with either study.

Schleiss said study reported in Cell Stem Cell is a “very, very important paper,” demonstrating that Zika can kill brain cells while offering a framework for understanding how the virus might be causing microcephaly.

The NEJM research, which followed 88 pregnant women in Brazil, provided “a rather frightening and sobering” perspective, showing that out of 42 women who had an ultrasound exam, 29 per cent had abnormal results.

“The risk is really probably much higher, as reported in this paper, than what any of us would’ve predicted,” Schleiss said. “So we may just now be seeing the beginning of an increasing epidemic with even more cases. It is very sobering.”

In the Cell Stem Cell paper, U.S. researchers used lab-grown human stem cells to show that Zika can infect cells that form the brain’s cortex. Infected cells were then more likely to die and less likely to divide normally.

“We’re literally the first people in the world to know this, to know that this virus can infect these very important cells and interfere with their function,” said lead author, Hengli Tang, a virologist with Florida State University.

The NEJM paper, on the other hand, is the first “prospective cohort study” of Zika and newborn malformations — meaning U.S. and Brazilian researchers enrolled a group of women and followed them over the course of their pregnancies.

The 88 pregnant women included in the study all developed a rash within five days of being treated by a clinic with the Oswaldo Cruz Foundation in Rio de Janeiro. Seventy-two had blood or urine samples that tested positive for Zika virus between September 2015 and mid-February.

Of the 42 women who consented to ultrasound exams, 29 per cent had abnormal results, according to senior author Dr. Karin Nielsen, a professor and infectious pediatric disease expert with UCLA’s David Geffen School of Medicine. “In a healthy population, it’s usually around 1 per cent or 2 per cent at most,” she said.

By comparison, all 16 women who were not infected by Zika had normal ultrasounds.

The abnormal results included not just microcephaly but also “intrauterine growth restrictions” and brain malformations. Of the eight babies born so far, two were stillborn and three have microcephaly or brain calcifications, according to Nielsen. Two also suffer from retinal impairment, indicating they will probably suffer from vision problems.

Nielsen was surprised that even women infected during their third trimester experienced serious outcomes, including stillbirths and one baby at 40 weeks who had no amniotic fluid.

“Zika seems to be a problem when there is an infection in women in any trimester of pregnancy,” she said. “They’re not out of the woods just because the first trimester is over.”

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Nielsen said Brazil is now suffering a “perfect storm” because this surge in microcephaly is converging with a struggling economy and failure to control the mosquito that spreads Zika. “This will be a big burden on the country,” she said. “Children with brain disorders are very expensive to follow and to maintain, and need a lot of services.”

According to the WHO, only two countries have reported an increase in microcephaly cases during a Zika outbreak so far: Brazil and French Polynesia, which suffered an outbreak in 2013 and 2014.

But this week news reports indicated that Colombian scientists have confirmed their first cases of birth defects associated with Zika. A large prospective study involving roughly 5,000 pregnant women, mostly in Colombia, is still underway, however, and final results probably won’t be available until June, according to WHO.

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