CHICAGO - Researchers on Wednesday reported new evidence strengthening the association between Zika virus and a spike in birth defects, citing the presence of the virus in the brain of an aborted fetus of a European woman who became pregnant while living in Brazil.

An autopsy of the fetus showed microcephaly or small head size, as well as severe brain injury and high levels of the Zika virus in fetal brain tissues, exceeding levels of the virus typically found in blood samples, researchers in Slovenia from the University Medical Center in Ljubljana reported in the New England Journal of Medicine.

The findings help “strengthen the biologic association” between Zika virus infection and microcephaly, researchers from the Harvard School of Public Health and Massachusetts General Hospital in Boston, wrote in an editorial that accompanied the paper. Researchers in Brazil are scrambling to find a link between the arrival of the Zika virus in that country and more than 4,000 suspected cases of microcephaly cases several months later. Moreover, top research institutions, funders and publishers said Wednesday they would make all scientific findings on the Zika virus assailing Latin America available speedily, and free.

A statement signed by the journals Nature, Science and The Lancet, the Chinese Academy of Sciences, France’s Institut Pasteur, the Bill and Melinda Gates Foundation and the Japan Agency for Medical Research and Development said data was a crucial tool in fighting the public health emergency.

“Journal signatories will make all content concerning the Zika virus free to access,” the document said. For their part, research funders will require scientists to share interim as well as final data as rapidly and widely as possible.

The route to publication can be a long, slow one, and research findings are usually not shared until after they have been published in a peer-reviewed journal. “The arguments for sharing data, and the consequences of not doing so, have been thrown into stark relief by the Ebola and Zika outbreaks,” the document stated. “In the context of a public health emergency of international concern, there is an imperative on all parties to make any information available that might have value in combatting the crisis.”

The statement urged other organisations to follow suit. Other signatories included Doctors Without Borders (MSF in its French acronym), The New England Journal of Medicine, PLOS Science Journals, the South African Medical Research Council and the Wellcome Trust.

The move was welcomed by experts as a sea change in public health research. Trudie Lang, director of the Global Health Network, said the response to Zika - even more so than in the case of Ebola - was being hamstrung by the many unknowns.

“We are still to prove that Zika causes microcephaly, and we need to know at what point damage happens in pregnancy, should this be the case,” she said in comments issued by the Science Media Centre in London. “In addition we need to develop better diagnostic tools and agree how to interpret anomaly scans to assess how these affected babies are developing.”

Data needs to be shared as quickly as possible, she said, “to address all these questions concurrently.” Lang also stressed the need to ensure the data is reliable and accurate. This “requires research sites to be well trained and have the resources they need to collect and manage data in ways that avoid error,” she said.

Infectious diseases professor Mark Woolhouse from the University of Edinburgh described the commitment as one of the most welcome developments in decades. “If acted upon, this declaration will save lives,” he said. An outbreak of the usually benign Zika virus in Latin America and the Caribbean has coincided with a surge in babies with microcephaly, a condition that causes them to have unusually small heads and brains, leading to death or disability.

No scientific proof has been found that Zika causes microcephaly, though the UN’s World Health Organization (WHO) has said a link is “strongly suspected” and has declared Zika a “public health emergency of international concern.” There is no cure or vaccine for the virus which, in most people, causes mild symptoms.